,,the ,,mysterious ,,box3 ,nuclear ,science and ,art by ,bernard ,keisch ,contents ,the ,mysterious ,box #b ,how ,old ,is a ,painting8 #aa ,who ,was the ,artist8 #bd ,other ,new ,tools for ,art ,authentication #cf ,one ,mystery ,solved #db ,reading ,list #dd ,united ,states ,atomic ,energy ,commission ,office of ,information ,services ,library of ,congress ,catalog ,card ,number3 #gj-fjfjdj #aigj2 #aigd 7rev47 ,the ,author ,illustration3 ,bernard ,keisch ,dr4 ,bernard ,keisch received his ,b4,s4 degree from ,rensselaer ,polytechnic ,institute and his ,ph4,d4 from ,washington ,university4 ,he is a ,senior ,fellow with the ,division of ,sponsored ,research of ,carnegie-,mellon ,university in ,pittsburgh4 ,he is presently engaged in a project that deals with the applications of nuclear technology to art identification4 ,this is jointly sponsored by the ,u4 ,s4 ,atomic ,energy ,commission and the ,national ,gallery of ,art4 ,previously he was a nuclear research chemist with the ,phillips ,petroleum ,company and senior scientist at the ,nuclear ,science and ,engineering ,corporation4 ,he has contributed articles on art authentication to a number of journals4 ,for the ,,aec1 in addition to this booklet1 he has written ,the ,atomic ,fingerprint3 ,neutron ,activation ,analysis1 ,secrets of the ,past3 ,nuclear ,energy ,applications in ,art and ,archaeology1 and ,lost ,worlds3 ,nuclear ,science and ,archaeology4 ,nuclear energy is playing a vital role in the life of every man1 woman1 and child in the ,united ,states today4 ,in the years ahead it will affect increasingly all the peoples of the earth4 ,it is essential that all ,americans gain an understanding of this vital force if they are to discharge thoughtfully their responsibilities as citizens and if they are to realize fully the myriad benefits that nuclear energy offers them4 ,the ,united ,states ,atomic ,energy ,commission provides this booklet to help you achieve such understanding4 ,the ,cover ,this painting1 originally believed to be the work of the ,dutch artist ,frans ,hals 7#aehj-afff71 is a fake4 ,measurements of the naturally radioactive isotopes1 polonium-#baj and radium-#bbf1 in lead white from the paint proved that it was no more than #ej years old4 ,illustration3 ,a ,van ,meegeren forgery of a ,vermeer4 ,the ,mysterious ,box ,the ,new ,jersey sun was high overhead and the day was hot4 ,the three boys walking along a deserted stretch of beach didn't mind because they were barefoot and in their swimsuits4 ,occasionally they would dash in and out of the surf to cool off4 ,suddenly ,martin let out a yell as his toe hit something hard hidden in the sand at the water's edge4 ,a moment later ,bill and ,harley were helping ,martin dig out a large wooden case4 ,it was heavy1 well built1 tightly sealed1 and had foreign words written on it4 8,maybe it's a pirate treasure chest10 said ,martin1 who was almost eight and had just read ,treasure ,island for the first time the week before4 8,you're crazy10 said ,harley1 who1 nearly ten1 was much older and wiser4 ,bill1 going on twelve1 thought aloud1 8,it must be something worthwhile2 maybe we can sell it and buy those model rockets we wanted40 ,the three boys soon found that they couldn't open the box and that it was too heavy to drag along the sand easily4 8,martin10 said ,bill1 8get ,dad while ,harley and ,i stand guard40 ,two hours later the box was at their house and everyone in the family was trying to read what was written on it4 ,about all that was readable was a large 8,u0 followed by what appeared to be two numbers4 ,some of the other marks looked like old ,german script and there was a date1 #aide4 8,you know10 said ,bill1 8,i bet that came from a ,world ,war ,,ii ,german submarine that our ,coast ,guard or ,navy sank40 8,let's open it up60 said ,harley as ,martin ran to get the screwdrivers4 ,inside they found a thoroughly waxed carton that they had to cut open4 ,everyone held their breath as their father lifted the top4 8,nothing but a bunch of pictures10 said ,martin who was still hoping for pirate treasure4 8,paintings can be worth a lot of money10 said ,dad1 8thousands or even millions of dollars40 8,well then we're rich60 yelled ,harley and ,bill together4 8,not so fast10 said ,dad4 8,first of all1 we don't know if the paintings are really valuable4 ,also1 it looks like these might be part of the art treasures that the ,nazis stole from the countries they conquered in ,world ,war ,,ii4 ,maybe someone was trying to get them by submarine to a neutral country1 like ,argentina1 just before the end of the war1 and the sub was sunk4 ,if they are real and stolen1 they'll have to go back to their rightful owners4 ,but cheer up1 maybe there's a reward40 8,how do we collect it80 asked ,bill4 8,if the ,nazis grabbed them1 aren't they real for sure80 8,not necessarily10 ,dad continued4 8,the ,nazis were fooled sometimes by people who sold them fakes4 ,there was one painting that ,hitler's sidekick1 ,gring1 bought that was supposed to be a #agth century painting by ,vermeer1 a ,dutch painter4 ,because ,vermeer's work is so valuable1 it's usually impossible to buy one for any amount of money4 8,vermeer is regarded as a national hero by the ,dutch4 ,the matter was investigated and the painting traced to ,han ,van ,meegeren1 a modern ,dutch painter who had only a fair talent4 ,when ,van ,meegeren realized he might be charged with treason by the ,dutch for selling a ,vermeer to the ,nazis1 he confessed that he had painted it himself4 ,he also confessed that he had painted other forgeries that fooled some of the experts and were sold for a lot of money4 8,many people1 however1 thought ,van ,meegeren was only lying to save himself from the charge of treason1 and the whole thing had to be decided by a committee of scientific art experts appointed by a court of law4 ,using the methods that were then available1 the experts showed that ,van ,meegeren had done a remarkable job of forgery and they were convinced that he had been telling the truth about painting those pictures4 8,at the time1 the important ways the experts used to examine a painting included studying the work with ,x rays1 which could show another painting underneath1 analyzing the pigments 7or coloring materials7 used in the paint1 and examining the painting for certain signs of old age4 ,illustration3 ,han ,van ,meegeren listens to the evidence at his trial in ,amsterdam4 ,in the background is 8,the ,blessing of ,jacob01 which was sold in #aidb as the work of ,vermeer4 ,illustration3 ,an authentic ,pieter de ,hooch work1 8,the ,card ,players01 painted in the #agth century4 ,illustration3 ,a forgery of a ,pieter de ,hooch picture painted in the #bjth century by ,han ,van ,meegeren4 ,illustration3 8,head of ,christ0 by ,van ,meegeren4 8,van ,meegeren was well acquainted with these methods4 ,he scraped the paint from old paintings that weren't worth much just to get the canvas and tried to use pigments that ,vermeer would have used4 ,he knew that old paint was very1 very hard and impossible to dissolve2 so he cleverly mixed a chemical 7phenolformaldehyde7 into his paint1 and this hardened into ,bakelite when he heated the finished painting in an oven4 8,for some of the paintings1 ,van ,meegeren became careless and the experts did find traces of a modern pigment 7cobalt blue7 in the paint4 ,they also found the ,bakelite4 ,for one or more paintings1 ,van ,meegeren did so well that1 in spite of all this evidence1 a few people still weren't convinced that these paintings were painted by ,van ,meegeren and not by ,vermeer40 ,bill1 who by this time was bursting with questions1 interrupted1 8,you mean they still aren't sure about some of those paintings after #be years8 ,aren't there better ways of telling whether a painting is genuine or not8 ,you're a scientist4 ,can't scientists like you do something about it now80 8,yes1 recently a method was developed to settle just such a question4 ,it's based on measurements of natural radioactivity in one pigment that all artists used hundreds of years ago4 ,and the method was applied to some of the ,van ,meegeren paintings including the best one of them all40 8,how did it come out80 asked ,martin4 ,illustration3 ,an ,x ray of part of the ,van ,meegeren forgery1 8,christ and ,his ,disciples at ,emmaus04 ,in the white circle are traces of paint from the original painting that ,van ,meegeren scraped off to obtain the old canvas4 ,when the painting was believed to be a genuine ,vermeer1 it was sold for about #cjj1jjj4 ,illustration3 ,the complete painting4 ,illustration3 ,a ,van ,meegeren forgery of a ,vermeer4 8,how does it work80 asked ,harley4 8,you mean paintings are radioactive80 exclaimed ,bill4 8,can we do it to the paintings we found80 asked all three together4 ,how ,old ,is a ,painting8 8,one question at a time4 ,i'll tell you how the method works and what it does if you're really interested40 8,we're interested6 ,we're interested60 chorused the boys4 8,in the first place1 this method works only in certain cases of suspected forgery4 ,over the last #ej or #ajj years1 a number of paintings have turned up that seemed1 even to the best art experts1 to be several hundred years old4 ,some of these were genuine1 and some were painted by forgers who could not resist the high prices paid for works of art4 ,the ,national ,gallery of ,art1 in ,washington1 ,d4 ,c41 thinking that there might be a way of detecting these forgeries1 gave its support to a group of scientists who developed a method for this purpose4 8,to understand how the method works1 you need to know a little about how radioactive atoms disintegrate to form atoms of other elements4 ,in this case we are interested in the natural radioactivity that occurs in certain rocks4 ,as a matter of fact1 in almost all rocks in the earth's crust there is a certain small quantity of uranium40 8,i thought uranium was rare10 interrupted ,bill4 8,it is1 but we're talking about such small quantities that its difficult for scientists using the most sensitive equipment to detect it4 ,the uranium in the rock decays to another radioactive element and that one decays to another1 and another1 and another1 and so forth1 in a series of elements that results in lead1 which is not radioactive4 ,in this series are two radioactive elements1 radium and a radioactive isotope of lead1 that help us to date paintings4 ,to understand this1 we must first understand how radioactive elements decay4 8,all radioactive elements have what is known as a #8half-life'2 that is1 in a certain period of time1 half of the element disintegrates to another form4 ,in another equal period of time1 half of what is left disintegrates1 and then half again1 and so on4 ,in the case of the uranium1 which starts the series ,i am describing1 the half-life is over #d1jjj1jjj1jjj years4 ,because of its long half-life there is plenty of uranium around and will be for a long1 long time4 ,on the other hand1 radium1 which ,i mentioned a moment ago1 has a half-life of only #afjj years4 ,in #afjj years1 half of it would be gone1 and in another #afjj years half of that would be gone1 and so on4 8,the radioactive lead that we're interested in has a half-life of only #bb years4 ,this means that if you start with a small quantity of this radioactive isotope of lead1 which is called lead-#baj1a then in only a few hundred years it would have disappeared4 ,however1 in rock1 where there is uranium1 the uranium keeps feeding the elements following it in the series1 so that as fast as they decay they are reproduced by the element before them40 ,illustration3 ,the ,uranium ,series4 ,in this simplified diagram1 the double vertical arrows represent alpha radioactivity and the single slanted arrows represent beta radioactivity4 ,the times shown on the arrows are the half-lives for each step4 ,uranium-#bch #d billion years ,thorium-#bcd #bd days ,protoactimum-#bcd #a minutes ,uranium-#bcd million years ,thorium-#bcj #hj thousand years ,radium-#bbf #afjj years ,radon-#bbb #c days ,polonium-#bah #c minutes ,lead-#bad #bg minutes ,bismuth-#bad #bj minutes ,polonium-#bad less than one second ,lead-#baj #bb years ,bismuth-#baj #e days ,polonium-#baj #ach days ,lead-#bjf 7,not ,radioactive7 8,i don't quite understand how that works10 said ,harley4 8,what do you mean #8it keeps feeding it'80 8,well1 think of a series of lakes connected by waterfalls4 ,at the top1 the highest lake has an enormous supply of water4 ,following the waterfall coming out of the lake you find a smaller lake and then maybe a medium-sized lake1 and after another waterfall1 a smaller lake1 then a tiny lake1 and so on4 8,as long as that big lake on top is full or nearly full1 all the other lakes1 whether they are small or medium-sized1 will still be getting water as fast as it pours out4 ,but if you cut off the supply of water from the upper lake to the next lake1 then the smaller lakes will in time run dry4 ,the same thing works with the radioactivity4 ,in this series headed by uranium1 as long as uranium is present all the other elements below it are kept supplied so that they don't run out40 8,i understand that10 said ,bill1 8but how do we use that to date a painting80 8,one of the pigments used by artists for over #bjjj years is known as lead white and it is made from lead metal4 ,the lead metal in turn is extracted from a rock called lead ore1 in a process called smelting4 ,the radioactive lead1 this lead-#baj that ,i mentioned1 behaves like ordinary lead metal and goes along with it4 8,the radium1 which has a fairly long half-life1 doesn't follow the lead metal1 but is removed with other waste products in a material called slag4 ,since the longer-lived ancestor of the lead-#baj is removed1 the supply of lead-#baj is cut off4 7,or we can say that one of the waterfalls is shut off47 ,the lead-#baj will then decay with its #bb-year half-life40 ,illustration3 ,the radioactive series that starts with uranium is like a series of lakes connected by waterfalls4 ,as long as uranium1 the big one on top1 has water in it1 the others will be full and the falls will keep flowing4 ,but when the first waterfall is shut off1 the small lakes below it will run dry4 8,i get it10 said ,bill4 8,that means that when you take a sample of old lead white paint1 there shouldn't be any radioactive lead-#baj left40 8,that's right4 ,but that would only be true if you removed all the radium4 ,actually1 in the smelting process it's more usual to remove only #ij or #ie of the radium4 ,in that case1 the lead-#baj would decay only until the amount left would be equal to the small amount of radium that wasn't removed4 ,in effect1 this would be like shutting off only part of the waterfall40 8,so what do you find10 asked ,harley1 8if you measure the radioactivity in a sample of lead white paint80 8,we find that if the paint is old1 compared to the #bb-year half-life of the lead1 let's say #ajj years old or more1 then the amount of radioactivity from the lead-#baj in the sample of paint will be equal to the amount of radioactivity from the radium in the sample4 ,but if the paint is modern1 let's say only #bj years old or so1 then the amount of radioactivity from the lead-#baj will be greater than the amount of radioactivity from the radium40 ,martin1 who had been quiet through all this explanation1 finally spoke up4 8,well1 was it finally tried out8 ,how did it work80 8,hundreds of samples were analyzed4 ,these samples were taken from paintings of all ages1 from some over #cjj years old right up to others only a couple of years old4 ,the old samples always showed equal amounts of radioactivity from lead-#baj and radium while the modern ones always showed larger amounts of radioactivity from lead-#baj than from radium4 ,that meant that scientists had a way of definitely telling if a lead white paint was modern or not4 8,eventually1 the method was tried on a number of paintings believed to be by ,van ,meegeren4 ,sure enough1 every one of them showed that the paint couldn't possibly have been more than #cj or #dj years old and that ,van ,meegeren probably was telling the truth when he said that he had painted them4 ,the paintings certainly were not genuine ,vermeers from the #agth century40 8,okay1 ,dad10 said ,martin1 8can we use the method on any of the paintings we found8 ,are any of these paintings supposed to be old enough so that we can use this test80 8,not so fast4 ,to find that out we have to do a lot of checking first40 8,how do we go about it80 asked ,bill4 8,let's see now4 ,there are nine paintings in the box you found4 ,the first thing we should do is take them down to a museum or gallery and let the art experts look at them4 ,since we have a few weeks of vacation time left1 what do you say we take a trip down to ,washington1 ,d4 ,c41 and show them to some experts at the ,national ,gallery of ,art80 ,over the next few weeks quite a few things happened to the boys and their paintings4 ,three of them were discarded right away because they were immediately recognized as being copies of no value4 ,two were relatively modern paintings with the signature ,alfred ,sisley2 if genuine1 they were less than #ajj years old4 ,the remaining four appeared to be very old paintings4 ,two of them seemed to correspond to paintings that disappeared during the ,second ,world ,war4 ,photographs and ,x rays were taken and sent to the museum in ,holland1 which had owned the missing pictures1 so that they could make a preliminary examination4 ,illustration3 uncaptioned ,radioactivity of ,lead-#baj ,lead-#baj decaying with a half-life of #bb years4 ,when no radium is present there is almost none left after #f half-lives or #acb years4 ,radioactivity of ,radium-#bbf ,over the same period of time1 a small amount of radium decays very little because its half-life is about #afjj years4 ,radioactivity of ,radium #bbf ,radioactivity of ,lead-#baj ,but when lead-#baj decays in the presence of radium-#bbf1 the radioactivity of the lead-#baj only decreases until it is equal to the radioactivity of the radium4 ,that left two that could have been old but whose origins were unknown4 ,a series of simple chemical tests were begun on these and the boys watched experts take very small samples of paint for examination under the microscope4 ,after several months a list of the pigments present in the paintings was prepared4 ,all the pigments found were typical of old paintings and the ordinary examinations and tests couldn't prove whether the works were old or not4 ,finally1 it was decided that the only way to tell if these paintings were truly old was to apply the test that ,dad had described to the boys4 ,the boys watched a painting restorer remove samples of nearly white paint right at the edge of the paintings4 ,he worked carefully1 using a very sharp scalpel and a stereo-binocular microscope1 through which objects appeared to be sixty times larger than they really were4 ,the sample of paint weighed approximately twenty-thousandths of a gram4 ,the boys and their father took the samples to a radiochemical laboratory where they watched a radiochemist do the required analysis for lead-#baj and radium in the samples4 ,first the chemist dissolved the paint in acetic acid4 ,this removed the lead white from the oil and from the small amounts of other pigments in the paint4 ,the solutions were then heated and stirred with a silver disc hanging in the liquid4 ,after several hours the disc still looked clean1 but the chemist said that a radioactive element1 polonium-#baj1 was now plated onto the silver4 ,polonium-#baj is a member of the uranium series following the lead-#baj1 and a measurement of its radioactivity would be an accurate measurement of the radioactivity of lead-#baj4 ,the silver discs prepared from the two samples were each placed in an instrument called an alpha-particle spectrometer4 ,this instrument is extremely sensitive and can measure the very small amounts of polonium-#baj prepared from the tiny sample of paint that they started with4 ,while the instruments were making the measurements1 which took a couple of days1 the chemist turned to the remaining solutions and began the analyses for radium4 ,illustration3 ,a painting being sampled under a stereo-binocular microscope4 ,illustration3 ,lead white weighing twenty-thousandths of a gram 7#bj milligrams74 ,this is the amount needed to measure lead-#baj and radium-#bbf to determine if the lead white is old4 ,in a series of chemical steps1 he purified the solutions1 removing the lead and other materials so that finally he had a small amount of solution that contained little else but the original radium and a very small amount of barium 7an element that he deliberately added and one which is very similar to radium in its chemical properties74 ,by adding dilute sulfuric acid1 he prepared an insoluble material1 barium sulfate1 which was barely visible suspended in the solution4 ,illustration3 ,polonium plating apparatus4 ,a heated solution of lead white in acetic acid is stirred with silver discs for #d to #h hours4 ,illustration3 ,the disc above appears clean after removal1 but on its surface it retains a minute amount of polonium which can be measured4 ,by forcing the solution through a special thin plastic filter having tiny holes1 the particles of barium sulfate together with the radium that had been in the solution were caught on the surface of the filter4 ,this was mounted on a solid disc so that it too could be placed in the alpha-particle spectrometer for the measurement of radioactivity from the radium4 ,two weeks later the results were ready4 ,dad1 the boys1 and one of the experts from the museum met with the chemist to discuss them4 ,for one of the two paintings1 the polonium-#baj radioactivity was about ten times that of the radium activity4 ,the boys were disappointed because this meant that the painting could not have been #cjj or #djj years old as it first appeared to be4 ,illustration3 ,an alpha-particle spectrometer is used to measure the radioactivity of the radium and polonium prepared from the lead white4 ,illustration3 ,a plastic disc on which is cemented a filter containing a nearly invisible deposit of barium sulfate 7,ba,s,o7 that 8carried0 the radium4 ,but in the second painting the radioactivity from the polonium-#baj and from the radium-#bbf were just about equal4 ,that meant that this painting was at least #ajj years old and1 from its appearance1 probably more4 ,the boys were excited4 8,we have a really valuable painting60 said ,martin4 8,not so fast1 boys10 cautioned ,dad4 8,we don't know who painted it and we don't know exactly how old it is40 ,the ,gallery's expert was happy too4 ,he believed that the second picture was a genuine ,dutch painting from the #agth century4 ,it was a landscape and the artist might have been ,aelbert ,cuyp4 ,illustration3 8,the ,maas at ,dordrecht01 a genuine painting by ,aelbert ,cuyp4 8,what do we do now80 asked ,harley4 8,how can we prove that the painting was painted in ,holland in the #agth century by ,cuyp80 8,there is a method now being developed10 said ,dad1 8that could give us that kind of information40 8,how does it work80 ,martin asked4 ,who ,was the ,artist8 8,do you know how criminals are caught by using fingerprints80 asked ,dad4 8,sure we do10 said ,martin4 8,each person has a set of fingerprints that is different from anyone else's40 ,harley spoke up4 8,did the artist leave his fingerprints on the paintings80 8,probably not10 said ,dad4 8,besides1 they would have been wiped off long ago4 ,also1 who knows what each artist's fingerprints were like80 8,then what do you mean80 asked ,bill4 8,what ,i mean is1 there is another kind of #8fingerprint' that scientists are just now learning to use in all kinds of identification problems4 ,it's not really a fingerprint1 but it's just as distinctive as a real fingerprint4 8,you see1 in every material1 no matter how pure you try to make it1 there are always other substances contained in it in very1 very small quantities1 which are there only by chance4 ,usually the person making or using that material doesn't even know they are there1 and the quantities are so small they don't do any harm4 ,during the last several years1 scientists have developed extremely sensitive methods of analysis1 which have been applied to all kinds of problems4 8,one such method is called neutron activation analysis4 ,in this method these small amounts of impurities can be detected in tiny samples of material4 ,this is quite important because only very small samples can be taken from a precious painting without damaging it4 ,normally1 a scientist or an art restorer takes samples that are no bigger than the head of a pin40 8,how can you do anything with a sample that small80 asked ,bill4 ,illustration3 uncaptioned 8,with neutron activation analysis you can do a great deal4 ,to give you an example of how sensitive this method is1 think of a bathtub containing #ejj quarts of milk4 ,add #a drop of an acid containing a speck of gold dissolved in it4 ,after you mix the acid and milk thoroughly1 you won't be able to tell by looking at it that anything was added4 ,but if you take a thimble full of liquid out of the bathtub1 you can easily tell with neutron activation analysis that gold was added to the milk4 8,scientists call low concentrations of accidental impurities #8trace elements'1 and the amounts that are present are measured in parts per million rather than percent4 ,one part per million is one ten-thousandth of a percent40 ,bill spoke up again4 8,so how does that make a fingerprint1 ,dad80 8,it works this way4 ,suppose an artist used lead white in several paintings4 ,now if the lead white were absolutely pure it would contain only lead1 carbon1 oxygen1 and hydrogen4 ,but the lead white the artist used would also contain very small quantities of other elements1 these trace elements that ,i spoke of4 ,in that particular batch of lead white1 certain trace elements will be present in a certain quantity4 ,the kind and amount of the trace elements will be present in that exact pattern only in that batch of lead white4 8,now suppose you analyze the lead white from several paintings that you know were painted by that particular artist1 and you find that there is silver1 mercury1 antimony1 tin1 and barium in every one of the samples4 ,also1 each of these elements is always present in a certain concentration4 ,suppose also1 that you have a painting which looks like it was painted by that particular artist but you're not quite sure4 8,well1 if you take a sample of lead white from that unknown painting and you find that the pattern of impurities is the same as in the paintings you knew were genuine1 then the #8fingerprints' match4 ,the chances of duplicating impurities of this kind by pure accident are extremely small1 just about as small as the chances of finding two people with the same fingerprints4 ,that's why we call this a #8fingerprint method'40 8,that sounds like a good idea10 said ,harley4 8,who thought it up80 x one part per million 7ppm7 ,a known ,rembrandt4 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x silver chromium zinc manganese iron cobalt ,unknown painting ,a x x x x x x x x x x x x x x x x x x x x x x x x x x x x silver chromium zinc manganese iron cobalt ,unknown painting ,b x x x x x x x x x x x x x x x x x x x x x x x x x x x x x silver chromium zinc manganese iron cobalt ,known forgery x x x x x x x x x x x x x x x x x x x x x x x x x x x x silver chromium zinc manganese iron cobalt ,match the patterns of these lead white 8fingerprints04 ,unknown painting ,a is not a ,rembrandt2 it is by the same forger who painted the known forgery at the bottom4 ,unknown painting ,b is either by ,rembrandt1 one of his fellow citizens1 or one of his students using the same paint4 8,it was thought of many times by many people4 ,but1 it's never been used for identifying paintings4 ,in #aifd in the ,netherlands1 two scientists1 named ,houtman and ,turkstra1 analyzed about #dj different samples of lead white1 #bj of which came from ,dutch and ,flemish paintings4 ,the rest were samples of lead white not taken from paintings but obtained directly from the manufacturers4 ,they analyzed these samples for different elements4 ,these included silver1 mercury1 chromium1 manganese1 tin1 antimony1 and a couple of others4 8,they found that the concentrations of these elements in the lead white from all the old ,dutch and ,flemish paintings were very similar4 ,and the trace element concentrations were quite different in the modern lead white samples analyzed in the same way4 ,at the time1 they presumed that it was because the lead white in the paintings was manufactured so long ago4 ,they may have been right to a certain extent4 8,for example1 they found that in all the old paintings there were from #aj to #cj parts per million of silver in the lead white1 while in the modern samples of this pigment there were generally less than #aj parts per million of silver4 ,all of them had been painted before the #aith century1 and all the samples of pure lead white were manufactured during the latter part of the #aith century or during the #bjth century4 ,they believed that the reason the silver concentration was lower in the more modern material was because during the #aith century1 lead refiners were doing a better job of removing all the valuable silver from lead4 ,illustration3 ,silver concentrations in lead white4 ,the concentrations generally decreased after the middle #ahjjs4 ,notice also how the concentrations were very similar for all the older paintings 7before #agjj7 which were ,dutch or ,flemish4 8,however1 in #aifg in ,germany1 two men1 named ,lux and ,braunstein1 discovered that in some old paintings produced in ,italy1 lead white also contained low quantities of silver just like modern material4 ,they believed that the higher concentrations of silver in lead white were typical of ,dutch and ,flemish painters while the lower concentrations were typical of ,italian paintings of about the same age4 8,the whole case is still unsettled because not enough measurements have been made to show how reliable this method can be4 ,that is1 no one knows if samples of paint from several paintings by one artist would all have the same pattern of impurities in the same pigment4 ,it may be that of the many pigments present in an artist's paintings only a few will be suitable for use in this #8fingerprinting' method40 ,illustration3 ,quartz vials 7right7 containing samples are sealed in the aluminum can on the left4 ,they are then bombarded with neutrons in a reactor like the one in the picture below4 8,it sounds complicated10 said ,bill4 8,it is1 and it's going to take years of work before the method is proven1 if it is at all4 ,it may turn out that you can't tell one artist from another1 but only groups of artists like #agth century ,dutch painters or #aith century ,english painters40 8,tell us something about neutron activation analysis10 said ,martin4 8,how do you measure such small amounts of impurities80 8,the best way to tell you how this works is to show you4 ,how would you boys like to visit a laboratory where neutron activation analysis is being done80 8,do you have to ask80 said ,harley4 8,of course we would60 ,a few weeks later it was all arranged4 ,at a laboratory close by a nuclear reactor1 the boys watched a radiochemist place a few specks of material inside small quartz tubes that were then sealed4 ,the tubes were put in an aluminum can and placed in the nuclear reactor4 ,the can was fastened on the end of a long pole that was then submerged in a deep pool of water4 ,at the bottom of the pool the boys could see a bright blue glow4 ,illustration3 ,this type of nuclear reactor is used for neutron activation analysis4 8,so that's what a nuclear reactor looks like60 said ,bill4 8,yes10 said ,dad4 8,where you see the blue glow you can also see rows of fuel elements4 ,each one contains slugs of uranium encased in aluminum4 ,this is one of a number of different types of reactors4 ,but every nuclear reactor is arranged so that the uranium atoms divide 7or fission7 many1 many times each second4 8,when this happens1 heat is produced that is carried away by the water1 and also many1 many free neutrons are produced4 ,those samples1 placed down next to the reactor in the bottom of the pool are being bombarded by the neutrons1 and some of the elements in the samples absorb the neutrons and become radioactive40 ,after a while the samples were removed and carried back to the laboratory in a lead box4 ,a short while later1 the radiochemist opened the aluminum can1 broke open the quartz capsules1 and removed the samples for analysis4 ,the boys watched the chemist mount each sample on a card and take it to a room where there was equipment for measuring radioactivity4 ,illustration3 ,gamma-ray spectrometer4 ,the sample to be measured is placed on a stand over a gamma-ray detector4 ,the pulse-height analyzer is a device that sorts electrical impulses from the detector according to the energy of the gamma rays causing the impulses4 ,the screen displays the gamma-ray spectrum and the electric typewriter automatically types out the data collected when the measurement is complete4 ,one by one the samples were placed inside a shield consisting of a big pile of lead bricks4 ,when the heavy door was opened1 the boys could see a metal can inside the shield1 which housed a detector 7called a lithium-drifted germanium detector7 that measured the gamma rays emitted by the sample4 ,as each sample was placed near the detector the chemist turned on a gamma-ray spectrometer to which the detector was connected4 ,a tiny sample of lead white sample is sealed in a quartz vial vial which is bombarded with neutrons in a reactor4 ,illustration3 uncaptioned ,many of the atoms become radioactive1 emitting gamma rays4 ,illustration3 uncaptioned ,the sample is placed in a gamma-ray spectrometer and the gamma rays are separated according to their energy4 ,illustration3 uncaptioned ,gamma-ray spectrum ,copper ,zinc ,antimony ,lead ,silver ,height ,antimony ,the location 7energy7 of each peak indicates what is present and the height indicates how much6 ,illustration3 ,a gamma-ray spectrum as it appears on the screen of a pulse-height analyzer4 ,the gamma-ray peaks are marked with the name of the element whose radioactive isotope emits the gamma ray2 two for cobalt and zinc and one for cesium4 ,there1 on what looked like a small television screen1 flashes of light appeared that gradually formed a curve with many peaks and valleys4 ,after a few minutes the spectrometer was stopped and an electric typewriter automatically typed out rows and columns of numbers4 ,the chemist explained1 8,this curve1 which you see on the screen1 is a gamma-ray spectrum and tells us what elements are in the sample4 ,the typed-out data give us an accurate measure of the shape of the curve on the screen4 ,by measuring the gamma-rays' energies we know what elements in the sample were made radioactive4 ,the height of each gamma-ray peak tells us how much of that element is present in the sample4 8,that gives us the information we need to calculate the concentrations of the small quantities of materials in our samples4 ,we can do this because at the same time ,i irradiated a set of standards4 ,standards are materials that are just like the samples except that they contain known amounts of the impurities ,i am trying to measure40 ,as the boys were leaving the laboratory1 the chemist apologized for not having enough time to explain the activation analysis procedure more thoroughly1 but he did give the boys a list of books to read on the subject of radioactivity and radioisotopes4#b ,they thanked him for his help4 ,during the ride home1 they discussed the paintings that were still unproven4 8,it's too bad that the method of activation analysis fingerprinting hasn't been fully developed yet10 said ,dad4 8,yes10 said ,bill4 8,then we could prove whether or not that last old painting was really by ,aelbert ,cuyp as the expert from the gallery believed4 ,but what about those paintings that we found in the box that were not so old80 8,well10 said ,dad1 8if the activation analysis method were workable1 we might be able to prove if they were painted by ,alfred ,sisley4 ,meanwhile1 until the method is really developed we don't know if we can do it that way or not40 8,so what do we do now80 asked ,martin4 8,we'll have to wait until scientists can thoroughly investigate this method and several others that they're working on40 8,other methods60 exclaimed ,bill4 8,what other methods80 ,illustration3 8,the ,banks of the ,oise01 a genuine painting by ,alfred ,sisley4 ,other ,new ,tools for ,art ,authentication 8,there are several new tools that scientists are working on now10 said ,dad4 8,these involve methods that have been developed by scientists for other purposes1 but are now being explored for use in authenticating works of art4 8,for example1 in ,los ,angeles1 the county museum purchased an instrument known as a ,spark ,source ,mass ,spectrometer4 ,like activation analysis1 this instrument will also measure small traces of impurities1 but they have just set that up and it will take them years to explore the use of it for the type of problem we have been discussing4 8,x-ray diffraction is another method that has been around for quite awhile but hasn't been used much for art identification until recently4 ,with ,x-ray diffraction1 samples of pigments can be identified by the pattern formed when ,x rays are bent by passing through the sample of pigment40 8,how's that80 asked ,harley4 8,there are #c or #d different compounds with about the same chemical composition as lead white4 ,chemically1 they are almost impossible to distinguish4 ,but with ,x-ray diffraction1 a chemist can easily tell them apart4 ,the hope is that the type of lead white will indicate how it was manufactured4 ,until the middle of the #aith century1 lead white was produced mainly by packing strips of lead in clay pots with a little vinegar in the bottom4 ,the clay pots were stacked in a large building with layers of decaying organic matter on the floor4 ,the building was sealed for several weeks during which time the lead corroded in the fumes and became covered with a white substance4 ,the white substance1 lead white1 was scraped off1 ground1 and washed to make the pigment4 8,but1 in the #aith century1 when people began to learn more about chemistry1 they looked for faster ways of making lead white and some of these methods produced a lead white of somewhat different composition4 ,by using ,x-ray diffraction1 chemists now hope that they can tell how the lead white was manufactured4 ,this may provide another means of dating the lead white in a painting40 8,are there any other methods80 asked ,harley4 ,illustration3 ,the stack process for making lead white4 ,rows of clay pots containing lead and vinegar are packed to the ceiling of the building1 and fermenting tanbark on the floor produces carbon dioxide and heat4 ,the fumes of vinegar and the carbon dioxide corrode the lead in #b to #d months1 and the corrosion is lead white4 8,yes1 isotope mass spectrometry is one4 ,all lead consists of #d different isotopes or atoms of different weights4 ,three of these #d are the end products of a radioactive decay chain4 ,depending upon the history of the rock formation in which the lead ore occurred1 the relative amounts of the lead isotopes vary in a special way4 ,in other words1 if we know the different amounts of lead isotopes in the world's lead ore deposits1 and we have a sample of lead white from a painting1 we can tell from which deposit the lead1 which formed the lead white1 came4 ,if1 for example1 we find that the isotope pattern in a sample from a painting is the same as in lead ore from ,australia1 then the painting can't be very old because lead white wasn't produced from lead mined in ,australia until about #ajj years ago40 ,illustration3 ,x-ray diffraction patterns from three different lead compounds that might occur in lead white4 ,the middle one is the ideal lead white produced for over #bjjj years4 ,while some of the bottom compound may be found mixed with it1 the compound shown at the top is only a #bjth-century invention4 #d,pb,c,o #b,,pb7,,oh7 ,pb,o #b,pb,c,o ,,pb7,,oh7 ,pb,c,o 8,how do you measure lead isotopes80 asked ,harley4 8,with an instrument called a mass spectrometer4 ,this instrument is capable of separating the lead isotopes4 ,first1 the atoms of lead in the sample are electrically charged and #8fired' in a beam down the length of a tube between the poles of a strong magnet4 ,there1 the charged atoms 7or ions7 in the beam are deflected by different amounts according to how heavy they are4 ,thus the different isotopes are separated4 ,this method is also still being studied and1 although it shows great promise1 it will be some time before it can solve problems of art identification4 ,also the study of the natural variation in isotopes of other elements1 such as sulfur1 is useful for identification of other pigments as well4 ,illustration3 ,diagram of a simple mass spectrometer4 ,the ionized atoms of lead travel in a beam at the same speed4 ,the heavier atoms bend less than the lighter ones when the beam passes the magnet4 ,thus two beams emerge instead of one4 ,actually there are four isotopes of lead so there will be four beams4 ,illustration3 8,agostina01 a genuine painting by ,jean ,baptiste ,camille ,corot4 8,another new method that shows great promise has been developed1 but this one is not applicable to the paintings that you boys found in the box40 8,why not80 asked ,bill4 8,since the ,second ,world ,war1 the art forgery business has been growing rapidly4 ,for example1 it has been said that of the #bjjj pictures that ,corot1 a #aith century ,frenchman1 is known to have painted1 more than #ejjj of them are in the ,united ,states4 ,this may be only a humorous exaggeration1 but a large number of forgeries have been produced in the last several years4 ,these are usually supposed to be paintings that are less than #ajj years old4 ,present-day forgers like to forge paintings that aren't very old because it's easier to get away with4 ,now this new method1 which will detect such recent forgeries1 is based upon the presence of carbon-#ad1 a radioactive isotope of carbon1 in our atmosphere and in all things that grow on our planet4 8,ordinarily1 carbon-#ad is produced only by cosmic rays1 and its concentrations in the atmosphere and in growing things would remain at a constant level4 ,but since the middle of the #aiejs the testing of nuclear weapons has increased the amount of radioactive carbon in our atmosphere by quite a bit4 ,many artist's materials1 such as linseed oil1 canvas1 paper1 and so on1 come from plants or animals1 and so will contain the same concentrations of carbon-#ad as the atmosphere up to the time that the plant or animal dies4 8,therefore1 linseed oil 7from the flax plant71 for example1 produced during the last few years will have a much greater concentration of carbon-#ad in it than linseed oil produced more than #bj years ago4 ,scientists at ,carnegie-,mellon ,university have shown that this method will work4 ,it is only a matter of making the measurements on the small samples available from presumably valuable paintings40 ,illustration3 ,the changing concentrations of carbon-#ad in our atmosphere4 ,high levels of carbon-#ad in linseed oil and other painting materials will indicate that a work of art is only a few years old4 ,carbon-#ad radioactivity ,older materials contain less as the carbon-#ad decays away4 ,in this period1 decrease is due to the burning of large quantities of coal and oil as industry grew4 ,this diluted the newly formed carbon-#ad4 ,increases due to testing of atomic weapons in the atmosphere4 ,carbon-#ad produced by cosmic rays only ,neutron ,nitrogen ,carbon-#ad proton ,carried down by rain in carbon dioxide 8,there are also a number of other methods being studied including the use of ,messbauer ,effect ,spectroscopy to study pigments that contain iron1 thermoluminescent dating of pottery and terra-cotta statuary1 ,x-ray fluorescence analysis as a general tool1 and neutron autoradiography as a means of studying the technique of artists4 ,you can read all about them if you wish40#c 8,it sounds like forgers are going to have a tough time in the future10 said ,harley4 8,that's right4 ,it may even turn out that producing forgeries to pass all these new tests will be so difficult and expensive that forgers will stop trying40 ,one ,mystery ,solved ,a year later an important letter arrived at the boys' house4 ,dad opened it1 read it quickly1 and said1 8,good news1 boys6 ,this letter is from the ,dutch government4 ,remember those two paintings that we thought might have been stolen from a ,dutch museum80 8,yes10 said ,bill4 8,well1 it seems that after a year of studying them1 the ,dutch have decided that they really are the paintings that were stolen40 8,that is good news10 said ,harley4 8,at least we know that two of the paintings we found are genuine40 8,what are they going to do with them80 asked ,martin4 8,of course1 they have to go back to their original owners4 ,but this letter says that the ,dutch government wants us to come to ,holland as their guests as a reward for finding those paintings40 ,illustration3 ,these two paintings 8,the ,lacemaker0 and 8,the ,smiling ,girl0 were thought to have been by ,vermeer4 ,a series of tests1 including some of those described in this booklet1 showed that the paintings are fairly old4 ,however1 some of the materials used are not typical of ,vermeer1 and the pictures are now thought to have been painted by a follower of the artist4 8,that's great60 said ,bill4 8,looks like we're getting something out of finding that box after all40 8,yes10 said ,dad4 8,and don't forget the other unidentified paintings may also be genuine4 ,we've proved that one is a fake1 the experts believe that three of the others are copies1 and then there are the two that might be ,sisleys and are only waiting for a method to prove it4 ,and we have one more that science managed to prove was really old4 ,i'm sure that in a few years methods will be developed to tell us exactly who painted it4 8,and now let's make arrangements for our trip to ,holland40 ,reading ,list ,about ,atomic ,power for ,people1 ,edward and ,ruth ,s4 ,radlauer1 ,childrens ,press1 ,chicago1 ,illinois #fjfjg1 #aifj1 #dg pp41 #b4ej4 ,grades #e-i4 ,all ,about the ,atom1 ,ira ,m4 ,freeman1 ,random ,house1 ,inc41 ,new ,york #ajjbb1 #aiee1 #adf pp41 #b4ej4 ,grades #d-f4 ,atoms at ,your ,service1 ,henry ,a4 ,dunlap and ,hans ,n4 ,tuch1 ,harper and ,row1 ,publishers1 ,new ,york #ajjaf1 #aieg1 #afg pp41 #d4jj4 ,grades #g-i4 ,carbon-#ad and ,other ,science ,methods that ,date the ,past1 ,lynn and ,gray ,poole1 ,mc,graw-,hill ,book ,company1 ,new ,york #ajjcf1 #aifa1 #afj pp41 #c4ie4 ,grades #i-ab4 ,experiments with ,atomics 7revised edition71 ,nelson ,f4 ,beeler and ,franklyn ,m4 ,branley1 ,crowell ,collier and ,macmillan1 ,inc41 ,new ,york #ajjbb1 #aife1 #afj pp41 #c4ej4 ,grades #e-h4 ,the ,fabulous ,isotopes3 ,what ,they ,are and ,what ,they ,do1 ,robin ,mc,kown1 ,holiday ,house1 ,inc41 ,new ,york #ajjbb1 #aifb1 #ahi pp41 #d4ej4 ,grades #g-aj4 ,inside the ,atom 7revised edition71 ,isaac ,asimov1 ,abelard-,schuman1 ,ltd41 ,new ,york #ajjai1 #aiff1 #aig pp41 #d4jj4 ,grades #g-aj4 ,introducing the ,atom1 ,roslyn ,leeds1 ,harper and ,row1 ,publishers1 ,new ,york #ajjaf1 #aifg1 #bbd pp41 #c4ie4 ,grades #g-i4 ,our ,friend the ,atom1 ,heinz ,haber1 ,golden ,press1 ,inc41 ,new ,york #ajjbb1 #aieg1 #afe pp41 #d4ie 7out of print but available through libraries72 #j4ce 7paperback7 from ,dell ,publishing ,company1 ,inc41 ,new ,york #ajjag4 ,grades #g-i4 ,radioisotopes1 ,john ,h4 ,woodburn1 ,j4 ,b4 ,lippincott ,company1 ,philadelphia1 ,pennsylvania #aiaje1 #aifb1 #abh pp41 #c4ej4 ,grades #g-aj4 ,the ,story of ,atomic ,energy1 ,laura ,fermi1 ,random ,house1 ,inc41 ,new ,york #ajjbb1 #aifa1 #ahd pp41 #a4ie4 ,grades #g-aa4 ,the ,useful ,atom1 ,william ,r4 ,anderson and ,vernon ,pizer1 ,the ,world ,publishing ,company1 ,new ,york #ajjbb1 #aiff1 #ahe pp41 #e4ge4 ,grades #g-ab4 ,working with ,atoms1 ,otto ,r4 ,frisch1 ,basic ,books1 ,inc41 ,publishers1 ,new ,york #ajjaf1 #aife1 #if pp41 #c4ej4 ,grades #i-ab4 ,footnotes #a;,it is called this because #baj is the total number of protons and neutrons in its nucleus4 #b,see the reading list on page #dd4 #c,see ,secrets of the ,past3 ,nuclear ,science and ,archaeology1 which is listed on the inside back cover of this booklet4 ,,photo ,,credits ,cover courtesy ,groninger ,museum voor stad en ,lande ,page #e ,yale ,joel1 ,life magazine1 copyright ,time1 ,inc4 #f ,her ,majesty the ,queen1 copyright reserved #g #h ,ullstein ,bilderdienst #aj ,rijksmuseum1 ,amsterdam #bc ,national ,gallery of ,art1 ,washington1 ,d4 ,c41 ,andrew ,mellon ,collection #ce #dj ,national ,gallery of ,art1 ,washington1 ,d4 ,c41 ,chester ,dale ,collection #dc ,national ,gallery of ,art1 ,washington1 ,d4 ,c41 ,andrew ,mellon ,collection ,u4,s4 ,,government ,,printing ,,office3 #aigd--gdg-eef_/ae ,the ,u4 ,s4 ,atomic ,energy ,commission publishes this series of information booklets for the general public4 ,the booklets are listed below by subject category4 ,if you would like to have copies of these booklets1 please write to the following address for a booklet price list3 ,,usaec--,technical ,information ,center ,p4 ,o4 ,box #fb ,oak ,ridge1 ,tennessee #cghcj ,school and public libraries may obtain a complete set of the booklets without charge4 ,these requests must be made on school or library stationery4 ,chemistry ,,ib-#cjc ,the ,atomic ,fingerprint3 ,neutron ,activation ,analysis ,,ib-#cja ,the ,chemistry of the ,noble ,gases ,,ib-#cjb ,cryogenics3 ,the ,uncommon ,cold ,,ib-#cjd ,nuclear ,clocks ,,ib-#cjf ,radioisotopes in ,industry ,,ib-#cjg ,rare ,earths3 ,the ,fraternal ,fifteen ,,ib-#cjh ,synthetic ,transuranium ,elements ,biology ,,ib-#aja ,animals in ,atomic ,research ,,ib-#ajb ,atoms in ,agriculture ,,ib-#aje ,the ,genetic ,effects of ,radiation ,,ib-#aaj ,preserving ,food with ,atomic ,energy ,,ib-#ajf ,radioisotopes and ,life ,processes ,,ib-#ajg ,radioisotopes in ,medicine ,,ib-#aji ,your ,body and ,radiation ,the ,environment ,,ib-#bja ,the ,atom and the ,ocean ,,ib-#bjb ,atoms1 ,nature1 and ,man ,,ib-#dad ,nature's ,invisible ,rays ,general ,interest ,,ib-#jji ,atomic ,energy and ,your ,world ,,ib-#jaj ,atomic ,pioneers--,book #a3 ,from ,ancient ,greece to the #aith ,century ,,ib-#jaa ,atomic ,pioneers--,book #b3 ,from the ,mid-#aith to the ,early #bjth ,century ,,ib-#jab ,atomic ,pioneers--,book #c3 ,from the ,late #aith to the ,mid-#bjth ,century ,,ib-#jjb ,a ,bibliography of ,basic ,books on ,atomic ,energy ,,ib-#jjd ,computers ,,ib-#jjh ,electricity and ,man ,,ib-#jje ,index to ,,aec ,information ,booklets ,,ib-#caj ,lost ,worlds3 ,nuclear ,science and ,archeology ,,ib-#cji ,the ,mysterious ,box3 ,science and ,art ,,ib-#jjf ,nuclear ,terms3 ,a ,glossary ,,ib-#jac ,secrets of the ,past3 ,nuclear ,energy ,applications in ,art and ,archaeology ,,ib-#jag ,teleoperators3 ,man's ,machine ,partners ,,ib-#jad1 ,worlds ,within ,worlds3 ,the ,story of ,nuclear ,energy ,volumes #jae1 #jaf #a1 #b1 and #c ,physics ,,ib-#dja ,accelerators ,,ib-#djb ,atomic ,particle ,detection ,,ib-#djc ,controlled ,nuclear ,fusion ,,ib-#djd ,direct ,conversion of ,energy ,,ib-#daj ,the ,electron ,,ib-#dje ,the ,elusive ,neutrino ,,ib-#daf ,inner ,space3 ,the ,structure of the ,atom ,,ib-#djf ,lasers ,,ib-#djg ,microstructure of ,matter ,,ib-#dae ,the ,mystery of ,matter ,,ib-#daa ,power from ,radioisotopes ,,ib-#dac ,spectroscopy ,,ib-#dab ,space ,radiation ,nuclear ,reactors ,,ib-#eja ,atomic ,fuel ,,ib-#ejb ,atomic ,power ,safety ,,ib-#eac ,breeder ,reactors ,,ib-#ejc ,the ,first ,reactor ,,ib-#eje ,nuclear ,power ,plants ,,ib-#ejg ,nuclear ,reactors ,,ib-#eaj ,nuclear ,reactors for ,space ,power ,,ib-#ejh ,radioactive ,wastes ,,ib-#eaa ,sources of ,nuclear ,fuel ,,ib-#eab ,thorium and the ,third ,fuel ,illustration3 ,,aec logo ,u4 ,s4 ,,atomic ,,energy ,,commission ,office of ,information ,services ,transcriber's ,notes --,silently corrected a few typos4 --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4