I D EN TI FYI N G TH E REAL TH I N G
( Prepared by D. van der Reyden of SCMRE, for School for Scanning, Sponsor ed by t he Nat ional Park Serv ice and Managed by t he Nort heast Docum ent Conserv at ion Cent er , Sept em ber 11- 13, 1996, New York Cit y)
I N TROD UCTI ON
TH E POW ER OF " TH E REAL TH I N G"
H OW TO I D EN TI FY " TH E REAL TH I N G"
BI BLI OGRAPH Y
I N TROD UCTI ON
People oft en go t o m useum s, librar ies and archives t o see " t he real t hing." But " t he real t hing" can be " seen" in m any ways. Appearance can be observed on exhibit or on- line, or m easured in a laborat ory. How ever, m at erials and t echnology can be revealed only by st ylist ic, hist orical and scient ific analysis of " t he real t hing." The findings of t hese various t ypes of analysis by m useum specialist s ( such as curat ors, hist orians, scient ist s, archivist s, conservat ors and ot her expert s) can t hen be
com m unicat ed t o or " seen" by various audiences, ranging from t he general public t o scholars, visit ing on sit e or w orking on- line. The m edia t hrough which findings are " seen" can include exhibit s, publicat ions, com put er program s, lect ures and videos, produced wit h t he aid of ot her m useum professionals ( specializing in exhibit ion, regist rat ion, publicat ion, public relat ions, educat ion, research, collect ions
m anagem ent and com put er science) . But , consider t his: w hen you look at an im age on exhibit ion or on- line, do you know if t hat obj ect is " real" ? How can you t ell? Why does it m at t er?
TH E POW ER OF " TH E REAL TH I N G"
Why is " t he real t hing" so im port ant t o people? Obj ect s are valued not only for t heir appearance, but also for t heir t rem endous sym bolic power. Any obj ect can have sym bolic and visual pow er. How ever, only " t he real t hing" cont ains t he evidence t o support it s sym bolic and visual im port ance. Evident ial, art ifact ual, value is dependent on t he m at erial com posit ion of t he obj ect . Reconciling t he sym bolic, visual,
art ifact ual and evident ial value of " t he real t hing" requires t he convergence of st ylist ic, hist orical and scient ific analysis. Such expert ise is oft en provided by t he collaborat ion of m any expert s found in m useum s like t he Sm it hsonian.
What do people really see when t hey look at an obj ect on exhibit , in a book or on-line? What t hey act ually see is a virt ual realit y, based on t he appearance of t he real t hing. The appearances of obj ect s have t rem endous power t o alt er t he course of hist ory and hum an lives. But m ere superficial appearances can be m isleading. Consider, for inst ance, som et hing as sim ple as a m anuscript . I n fact , consider t hree fam ous m anuscript s: " Howard Hughes' Aut obiography," " Hit ler's Diary," and t he Morm on Church's " Salam ander Let t er." What do t hese docum ent s have in com m on? Each had t he pow er t o great ly influence issues of legal, hist orical or religious
Take, for inst ance, t he case of t he " aut obiography" of Howard Hughes. The reclusive m illionaire Hughes supposedly broke his seclusion t o dict at e an aut obiography t o aut hor Clifford I rving. Hughes lat er prot est ed t hat he had not com m unicat ed wit h I rving, and lengt hy lit igat ion began. No less t han t hree handw rit ing expert s
aut hent icat ed let t ers t hat I rving claim ed were from Hughes. These expert s at t ribut ed t he let t ers t o Hughes based on t he " fact " t hat t he size and t he spacing of t he words w rit t en in t he let t ers were charact erist ic of t he st yle of Hughes' own w rit ing. The result ing long and expensive legal disput e m ight never have been set t led, had not I rving finally confessed t o forging t he let t ers.
The case of t he " aut obiography" illust rat es t he legal im por t ance of verifying " t he real t hing." The case of t he " Hit ler diaries" illust rat es t he pot ent ial pow er of obj ect s t o revise polit ical and social hist ory. I n t he early 1980's Newsweek m agazine published a special report on " Hit ler's 'Secret ' Diaries: How t hey could rew rit e hist ory." The diaries w ere finally exposed as fakes; in part because som e of t he m at erials used t o m ake t hem were not invent ed unt il aft er Hit ler's deat h. Modern opt ical bright eners were det ect ed in t he paper when t he pages w ere exam ined under special illum inat ion ( such as ult raviolet light ) . The binding of t he diaries cont ained m odern synt het ic m at erials, ident ified when sam ples w ere exam ined under high pow ered m agnificat ion ( such as a st ereo or polarized light m icroscope) .
One of hist ory's m ost ext rem e cases of forged docum ent s t hreat ened t o underm ine one of t he world's m ost powerful religions. The case of t he " Freem an's Oat h" and t he " Salam ander let t er" , result ed in t he act ual loss of life. I n t he m id- 80's, a Ut ah dealer, Mark Hofm ann, present ed t he Morm on Church w it h a series of docum ent s, which if real would have great ly em barrassed t he Church. As suspicion grew about t he aut hent icit y of t he docum ent s offered by Hofm ann, he began t o feel cornered. To prot ect him self, and provide a diversion, he resort ed t o m urder, engineering t he deat h of t hree people by blowing t hem up wit h hom e- m ade bom bs. He event ually inj ured him self w hile t ransport ing new bom bs. When arrest ed, he ult im at ely confessed t hat he faked t he docum ent s; t o m ake t hem appear aut hent ic, he used hist oric paper and ink recipes. He claim ed t hat he even art ificially aged t he
docum ent s by oxidizing t hem w it h hydrogen peroxide. This is what lead t o his downfall and arrest in t he first place. His creat ions had becom e suspect when exam inat ion, under high powered m agnificat ion ( such as a st ereom icroscope) , revealed t hat t he ink's m edium of gum arabic was cracking in a st range m anner, t ot ally inconsist ent w it h w hat w ould happen during " nat ural" aging.
H OW TO I D EN TI FY " TH E REAL TH I N G"
How can you t ell t hat an obj ect is " t he real t hing" ? I dent ifying " t he real t hing" requires looking beyond t he m ere superficial surface appearance of obj ect s. Taking obj ect s at " face value" can lead people t o m isunderst and or m isrepresent t he t rue value of obj ect s. The legal, hist oric, social or scient ific significance of obj ect s depends on t hat obj ect 's being " t he real t hing" . Alt hough any obj ect can have " sym bolic value," only " t he real t hing" is w ort hy of it s " sym bolic value" by virt ue of it s evident ial value. Evident ial value can only be support ed by full and accurat e charact erizat ion of " t he real t hing." Charact erizing obj ect s such as a print or m anuscript s can require t he com bined expert ise of curat ors, hist orians,
• St ylist ic Analysis • Hist orical Analysis • Scient ific Analysis
St ylist ic An a lysis
St ylist ic analysis, based on a com parison of t he st yle of an unident ified obj ect t o a known body of work, can provide clues about t hree im port ant aspect s of t he origin of " t he real t hing"( 3)
• Place of Origin
• Period of Origin
• Purpose of Origin
Pla ce of Or igin : St yle m ay vary depending on where an obj ect originat ed. For inst ance, consider obj ect s from China or Europe ( I ll. 1 and 2) . Each of t hese geographic locat ions, or count ries, has dist inct ly different t radit ional designs and m at erials t hat charact erize obj ect s from t hose count ries. For exam ple, a print wit h Chinese charact ers m ight be expect ed t o be from China ( I ll. 1) . An im age show ing t he influence of West ern Civilizat ion m ight have European origins ( I ll. 2)
Pe r iod of Or igin : St ylist ic analysis can also provide clues as t o when an obj ect was m ade, such as during t he Vict orian or Modern period ( I ll. 2 and 3) . A m ix of classical m ot ifs from around t he world ( I ll. 2) m ight charact erize t he t im e of t he Vict orian Em pire ( I ll. 2) . On t he ot her hand, t ot al abst ract ion is generally considered a m odern phenom enon ( I ll. 3) .
Pu r pose of Or igin : St ylist ic analy sis should include an underst anding of t he purpose of an obj ect . For inst ance, t he st yle of a draw ing m ay vary depending on whet her it was proposed be a quick sket ch, a working sket ch, a preparat ory drawing, a det ail st udy, or a finished present at ion piece ( I ll. 2) . Clues t o purpose can be found in t he com posit ion of t he design, such as a few st rokes for a quick sket ch or m odeled shading for a finished piece. Clues can also be found in t he com posit ion of m at erials and t echniques, such as a draw ing hand- sket ched w it h chalk or a print hand- pulled from an et ched and inked m et al plat e.
St ylist ic analysis m ight lead t o t he ident ificat ion of t he general school or specific m aker responsible for " t he real t hing" , or t o which t he obj ect m ight be at t ribut ed. But som et im es an obj ect m ight appear t o be one t hing and act ually be anot her ( I ll. 4 and 5) . There are m any w ays in which " t he real t hing" m ight be im it at ed. Som e print ing processes ( such as soft - ground et ching or lit hography) , can accurat ely copy t he appearance of original drawings, wat ercolors, et c. Det ect ing t hese copies m ight require special illum inat ion t echniques ( such as raking light across t he surface of paper) or high m agnificat ion ( achieved by a st ereoscopic m icroscope) . One m odern day dilem m a for m anuscript collect ors are aut opens and signa signers t hat m ight have been aut horized by t he owner of t he signat ure. I n som e cases, such signat ures can be difficult t o det ect . Not all obj ect s are copied w it h an int ent t o deceive. But if a forger uses t radit ional m at erials and t echniques t o im it at e t he st yle of t he original, it can be especially difficult t o det ect whet her an obj ect is an original, a copy, or a fake.
t o t hink in t erm s of t he m aker's int ent : how det ails of t he design's com posit ion ( space, light , form , and lines) are define; how t he qualit ies of line and color are expressed; and how well- execut ed and charact erist ic of t he m aker t he piece is. Take, for exam ple, an original m anuscript ( i.e. w rit t en by hand) as com pared t o a forgery, also hand- writ t en. Forensic expert s not e t hat original m anuscript s generally have writ ing t hat show s speed, consist ency, uniform st rengt h, pressure and carelessness. There should be backflow of ink only where t he ink crosses over let t ers or where a refill of newer ink m ight backflow int o t he lines of t he old ink. Fiber alignm ent on t he paper surface can indicat e t he direct ion of a st roke t o confirm whet her it is correct . Words would rarely have breaks wit hin t hem , and t hey would begin and end wit h flying st rokes. A forged m anuscript , how ever, m ight show a slow , hesit at ing hand wit h uneven pressure and bot h bold and weak st rokes of ink int erm ingled. Let t ers m ight be rew orked, or show a t rem or not associat ed w it h age or ill healt h. Words m ight be st opped in t he m iddle and t hen com plet ed, w it h a puddle of ink backflow at t he j unct ure. Or t he ink m ight feat her in creases, indicat ing t hat t he paper was creased before t he ink was applied.
St ylist ic analysis can be confirm ed or count ered by hist oric and scient ific analysis.
H ist or ica l Ana lysis
To be " t he real t hing" , an obj ect m ust be m ade w it h m at erials and t echniques consist ent w it h t he st yle of t he obj ect and t he hist ory of m at erials and t echniques associat ed wit h t he t im e and place of origin of t he obj ect . To illust rat e, consider t he hist ory of paper m aking and m edia t echnology, w hich is in it self full of m yst ery and int rigue. An hist orical analysis of obj ect s on paper w ould need t o include inform at ion on
• Mat erials and Techniques of Paper Making
• Mat erials and Techniques of Media
M a t e r ia ls a n d Te chn iqu e s of Pa pe r M a k ing:
Alt hough t he origin of paper is disput ed, early Chinese hist ory records t hat in t he second cent ury AD, t he scribe Ts'ai Lun present ed t he Em peror w it h his invent ion of paperm aking. This invent ion, an obvious im provem ent over cum bersom e
on paper, ingredient s like st arches ( rice, pot at o) or prot eins ( glue, gelat in) can be dispersed in wat er. The fibers were t hen cast random ly upon a paperm aking m old. Each m old consist ed of a fram e holding a porous screen. Mold t ypes varied
depending on t heir origin, but each im part ed a charact erist ic im pression on t he sheet of paper. For inst ance, a paper m ade wit h a " laid and chain" m old ( like fine " ant ique laid" w rit ing paper) w ould have a pat t ern of a series of t hin, parallel t ranslucent lines ( laid- lines) linked w it h occasional perpendicular lines m arking t he locat ion of t he " chain" st it ches holding t he screens' laid- lines in place. This configurat ion act ually derives from early orient al m at s ( m uch like m odern bam boo place m at s) . " Wove" paper has, inst ead of parallel lines, a weave im pression im part ed by fabric or wire m esh screens.
One com m on charact erist ic of t rue " hand- m ade" papers is a " deckled edge" where slippery paper fibers gat her under t he m old fram e as w at er is dispelled. Anot her charact erist ic t hat can help det erm ine t he dat e and origin of papers is t he
" w at erm ark," t radit ionally form ed from a raised design on t he m old, but w hich can be falsified by a " dandy roll" im pression. Mold charact erist ics and finishing
t echniques can also affect surface t ext ure. For inst ance, rough paper surface t ext ure m ay be t he result of t he im pression of t he raised wires of t he paper m old or t he hairs of t he felt s used for couching. This gives paper it s so called right side, ( t he felt ed side) , and wrong side ( t he wire side which could cause skipping of t he m edia) . These don't have as m uch effect as t he sm oot h surface induced by calendaring, which is caused by rolling over wit h a st eel cylinder. This com pressed effect can be dist ort ed by t he sw elling of fibers follow ing exposure t o wat er. The paper m ight also be
finished by a coat ing, which could be dissolved by w at er or solvent s. Any coat ing can rest rain a paper or be cracked by expansion and cont ract ion of t he paper fibers. Types of coat ings would include t he carbonat e used for m et alpoint s, album en coat ing on a phot ograph, or a gelat in glaze t o increase t he int ensit y of som e colors, for inst ance in a Currier and I ves print , or a varnish on a paper m ap.
w it h alkaline agent s like calcium carbonat e, like m odern perm anent - qualit y office paper, t hese high alpha cellulose papers are relat ively st able.( 5)
The hist ory of paper cont inues t o be replet e wit h a seem ingly infinit e num ber of variables of furnish m at erials and form at ion t echniques, from addit ives like bleaches t o processes like fiber beat ing and supercalendering. And t his is t he inform at ion ext ract able from a single sheet of paper, by exam ining it in various light s, w it h different m agnificat ion, or by organic and inorganic analysis. For inst ance, wat erm arks on paper can be seen using raking or t ransm it t ed light . Modern
addit ives, or specific t ypes of st ains, m ight fluoresce special colors under ult raviolet light ( t he sam e w ay a whit e shirt washed in a det ergent wit h opt ical bright eners fluoresces in a disco blacklight ! ) . Ot her addit ives can be ident ified w it h m ore com plex inst rum ent s like X- ray Fluorescence or Dispersion ( XRF or XRD) , Fourier Transform I nfrared Spect roscopy ( FT- I R) , or Scanning Elect ron Microscopic im aging ( SEM) or Elem ent al Dispersive Spect roscopy ( SEM- EDS) . Fibers in a paper can be ident ified as st able cot t on or acidic ground w ood using sim ple analyt ical t echniques on a polarized light st age m icroscope.
M a t e r ia ls a n d Te ch n iqu e s of M e dia :
Added t o t he wealt h of inform at ion inherent in t he base support of obj ect s is t he inform at ion inherent in t he m edia found on obj ect s. Media can be defined as t he im age or script found on paper or ot her obj ect s. The hist ory of m edia is as t elling as t hat of paper.( 6) For inst ance, before t he advent of t he pencil, art ist s and draft sm en m aking finely det ailed draw ings had t o rely on a m et al st ylus dragged across a coat ed paper. Even t he invent ion and fat e of t he seem ingly ubiquit ous graphit e pencil was bat t ered by hist ory. The Napoleonic wars blocked t he t rade wit h England in graphit e. This lead t o adult erat ion of nat ural graphit e w it h clay t o creat e so- called art ificial graphit e in t he lat e 18t h cent ury. I t is easy t o ident ify bot h t hese form s of graphit e using SEM im aging. Pure graphit e consist s of plat elet s, w hile art ificial graphit e has plat elet s m ixed wit h clay spheres. Consequent ly, a draw ing w it h art ificial graphit e can not be dat ed earlier t han t he lat e 18t h cent ury regardless of w het her it s st yle is consist ent w it h an earlier t im e or not . Many m odern m edia are not w hat t hey claim t o be, and t his can m ake t hem difficult t o ident ify. None- t he-less, each t ype of m edia has charact erist ic applicat ion processes, com posit ions and aging propert ies. Media can be divided int o several cat egories based, for inst ance, on w het her it is applied by
• Draw ing
• Paint ing
• Print ing
D r a w in g M e dia : Early drawing m edia consist ed of friable m edia like charcoal and chalk. Like m edia used lat er, such as graphit e and past el, t hese m edia have low am ount s of binder rat ios and so t hey don't adhere t ight ly t o surfaces. Consequent ly, t hese m edia charact erist ically are friable and t end t o sm udge or sm ear wit h handling over t im e, unless housed in appropriat e w indow m at s and glazed wit h non- abrasive and non- st at ic m at erials.
cause a piece t o be m isident ified. Silver point can be reconvert ed t o it s original appearance by exposure t o hydrogen peroxide.
I nk, a t erm originally derived from encaust ic by w ay of " inchiost ro"( 7) has oft en been used as a w rit ing, paint ing and print ing m edium , alt hough it is usually applied in t hin w ashes rat her t han t hick im past o. I nk t radit ionally has cont ained binders of oil, glue, gum s, resins, and waxes m ixed wit h pigm ent s or dyes, part icularly in m odern " print er's ink" . Som e m odern inks, developed for gravure, cont ain
acrylics.( 8) I nks can be bot h friable and soluble, especially as t hey age, leading t o flaking and sm udging. I ron gall ink has special problem s ow ing t o it s acidit y ( from t he oxidat ion of it s iron com ponent ) , which can in severe cases cause it t o eat t hrough t he paper support . This can cause bot h loss of legibilit y because of st rike-t hrough, or acrike-t ual loss of paper. Modern inks, and especially felrike-t - rike-t ips, can be fugit ive, fading in light . They also t end t o be highly soluble. I nks low in carbon, like bist re, becom e invisible when exam ined under infrared illum inat ion.
Pa in t ing M e dia : I nk can also be used as a paint ing m edia if applied in a w ash of solvent . Paint ing m edia can be cat egorized in several ways, based on t he
com posit ion of colorant s and binders, such as t em pera, gouache, wat ercolor, oil and acrylic. For exam ple, gouache differs from w at er color in t hat it is an opaque for acrylics, can also be soluble in w at er. Oil paint is occasionally used on paper, and t he problem here is t w ofold. The oil paint layer m ay be st ronger t han t he paper and 15t h cent uries ( when it replaced encaust ic unt il superseded by oil paint ) regained popularit y in t he 19t h cent ury. Egg t em pera consist s prim arily of egg yolk, w hich is a nat ural em ulsion cont aining a drying oil t hat can t ake up t o a year t o dry. I t is not very flexible and can crack if t hickly applied. Egg em ulsified w it h oil is also used in t em pera. Glue t em peras use anim al product s such as casein ( m ilk) and gelat in ( skin, bones) and m ay have glycerine added t o reduce cracking and form alin t o reduce w at er solubilit y. Gum t em peras use plant product s ( sap) and t end t o be brit t le if applied t hickly. Gum arabic, used for t em pera ( em ulsified w it h drying oils) , gouache ( m ade flexible w it h honey, sugar or glycerine) and wat ercolor, m ay require a
preservat ive ( halogenat ed or chlorinat ed phenols, boric acid, or sodium benzoat e) and m ay be em ulsified wit h oils and resins and m ixed wit h ot her aqueous m edia. St arch, also derived from plant s, can be used as a base for t em pera em ulsions. Egg-oil em ulsions and casein t em peras com prise m ost com m ercially produced t em peras t oday since upon aging t o a m at t or sem i- m at t appearance t hey becom e insoluble in wat er. Those wit h oil em ulsions can be t hick and flexible, alt hough t hey can develop hairline cracking and discolor wit h age. The use of t em per was supplant ed by
Gouache, a generic t erm possibly derived from " gouazzo" or paint ing w it h glue size, t ypically has a gum arabic ( acacia) or dext rin ( st arch) binder; a filler or w hit e pigm ent t o provide body and highlight s, and a m at t appearance upon drying. Gouache t radit ionally is suscept ible t o surface m arring or cracking if applied t hickly, and rem ains w at er soluble, unless as in m odern t im es acrylic is added t o m ake it abrasion and wat er resist ant . Gouache is oft en confused wit h w at ercolor.
Wat ercolor differs from gouache in com posit ion ( having no w hit e filler for body or highlight s) , in appearance ( applied as a t hin w ash) , and propert ies ( less solubilit y and cracking aft er drying) . Wat ercolor becam e est ablished in t he 18t h cent ury, used t o illum inat e books and m anuscript s where t he fugit ive nat ure of such a lean m edium would be prot ect ed. However, in t he 19t h cent ury m oist or sem i- m oist wat ercolor was m ade by adding glycerine, replacing sugar or honey which were added t o im prove flexibilit y and reduce cracking of cakes of wat ercolors; ox gall or ot her surfact ant w et t ing agent s m ay be added t o reduce surface t ension and im prove flow. St udent grade wat ercolors m ay cont ain dext rin rat her t han gum arabic and m ay have fillers. While w at ercolor rem ains soluble, oft en t he appearance of a t hin w ash m ay not change since fine pigm ent s penet rat e and lodge wit hin paper support s. Highlight s are creat ed by t he reflect ion of t he paper.( 9)
Pr in t in g M e dia : Paint and ink have t radit ionally been used as print m edia. The cat egories of print s are based on in how t he m edia is applied. Print ing is a t ransfer process; m edia is t ransferred from one subst rat e t o anot her subst rat e. The t ransfer m et hods vary. There are several m aj or cat egories of print s: relief, int aglio,
planographic, st encil, and phot om echanical.
Relief print s are m ade by carving aw ay areas of a print ing block, usually w ooden, t o leave raised areas t hat carry t he ink. When t he block is placed in cont act w it h a piece of paper and pressed or rubbed, t he ink is pressed int o t he paper, som et im es
act ually indent ing or im pressing t he paper slight ly. This is especially apparent in Japanese woodblock print s or in let t erpress print s found in early broadsides and new spapers. The m aj or problem w it h relief print s is t hat t his dist inct im pression around t he inked areas, evidence of relief t echniques, could be flat t en or lost if im properly cared for or t reat ed.
I nt aglio print s are m ade by incising a plat e, usually m et al, by any of several
processes. The incisions are filled w it h ink, and t he plat e is w ipe so t hat t he surface is clean. The plat e is t hen invert ed ont o a dam p piece of paper and run t hrough a press t o force ink t o sit on t op of t he paper. As a result , t here is an ink build up on t op of t he paper, and a creased, st ret ched edge around t he im age edge know n as a plat e m ark. The raised ink is sensit ive t o abrasion, and t he plat e m ark m ay be weakened or flat t en. Occasionally t he plat em ark is even cut down or off by
insensit ive collect ors or fram ers who aim for a bet t er fit in an album or fram e. The plat e m ark is one bit of evidence for t he aut hent icit y of an int aglio ( alt hough t hey can be forged as well) and so it should never be cut down. When m at t ing, t he
Planographic print s, usually m onot ypes or lit hographs, are creat ed by placing a flat subst rat e, such as lit ho st one or piece of glass, w it h an inked design coat ing t he surface, against a piece of paper and exert ing pressure. This is charact erized by having a virt ually flat plane of bot h ink and paper w it h only t he slight est possible expansion of t he paper corresponding t o t he area of t he inked surface. This
t echnique is oft en used t o im it at e ot her m edia such as draw ings, et c. These print s are com m on and relat ively durable, and t hey pose relat iv ely few problem s for
housing, st orage, display and t reat m ent unless handcolored or glazed. One except ion t o t his is t he special case of m onot ypes. The im age is draw n direct ly on t he
planographic plat e, which can t hen be print ed only once, aft er which t he bulk of t he m edium is com plet ely t ransferred. Different t ypes of m edia can be used, so t hese print s m ay have problem s arising from different solubilit ies.
The st encil process involves allow ing ink or paint t o com e in cont act wit h only t he design areas of t he paper by essent ially blocking t he negat ive areas of t he paper in a variet y of ways. The ink is brushed or squeezed ont o t he paper around t he negat ive space or t hrough a blocked screen. Edges of im age color oft en have lit t le pinholes from burst air bubbles in squeezed paint .
Phot om echanical print s are dist inguished from " fine art s" print s in several w ays. Fine art s print s are hand- pulled in lim it ed edit ions since t he qualit y of print ed im age event ually changes as print ing plat es w ear down. Phot om echanical print s can be m ass- produced wit hout any change t o t he im age because t hey are m ade by t ransfer of an im age t o a m achine by a phot ographic process before print ing. The ink used in a phot om echanical is usually not wat er soluble and t ends t o be fairly durable, and t here are seldom any hand applied coloring or glazes w hich m ight be sensit ive. Consequent ly, phot om echanicals are not usually inherent ly fragile unless m ade of ground w ood pulp, and not inherent ly com plicat ed t o house, display or t reat . The phot oelect ric process is t hat used t o m ake phot ocopies bot h colored and non-colored. These print s should never be in cont act w it h vinyl as t he plast icizers can solubilize t heir m edia.
Scie n t ific Ana lysis
Det erm ining t he m at erials and t echniques of obj ect s m ay require not only st ylist ic and hist orical analysis, but also scient ific analysis ( Table 2) . There are m any ways t o cat egorize scient ific analysis of obj ect s. Obj ect s can be charact erized qualit at ively and/ or quant it at ively by using dest ruct ive or non- dest ruct ive chem ical or physical analysis of form at ion t echniques or furnish m at erials ( bot h organic and inorganic) . Qualit at ive analysis reveals what m at erials ( elem ent s or com pounds) are present . Quant it at ive analysis m easures how m uch of t he elem ent s or com pounds are present . The quant it y can be m easured num erically and t he num bers can be
m inerals ( like oxides of carbon) . Scient ific analyt ical t echniques can fall int o several broad cat egories:
• I llum inat ion
• Radiography
• Magnificat ion
• Elem ent al Analysis
• Propert y Measurem ent s
I llu m ina t ion : An obj ect 's m orphology ( size, shape, t ext ure) or opt ical propert ies ( color, gloss, et c.) can be revealed t hrough different w avelengt hs of light . The appearance of obj ect s changes depending on t he t ype of exam inat ion used.
Wavelengt hs of light can illum inat e, radiat e, and irradiat e obj ect s. For exam ple, light covered by red or yellow filt ers can reveal obscured w rit ing under st ains or in
shadows. Monochrom e sodium arc lam ps suppress chrom at ic aberrat ions in order t o penet rat e glazes or overlayers t o reveal signat ures.
Visible light , t he range t hat w e see norm ally, show s different t hings about an obj ect depending on whet her it is aim ed at t he obj ect from a spect ral, raking or t ransm it t ed angle or dir ect ion. Spect ral illum inat ion, aim ed direct ly ( or spect rally) at obj ect s shows us t heir color, shape and size, and reveals t he presence of surface coat ings or gloss. Raking light passes across t he surface of t he paper and dram at ically reveals paper and m edia t echniques and t ext ure, and dam ages t o t he surface of t he paper support ( like cockling) and m edia ( like flak ing binder) . Transm it t ed light , penet rat ing t hrough paper, can show m old charact erist ics and wat erm arks, as well as t ears or repairs. I t can also provide ot her inform at ion about t he t ype of m old on w hich t he paper w as cast , such as whet her it w as of a laid and chain t ype or wove t ype. By show ing variat ions in densit ies, it displays fiber dist ribut ion, which indicat es how t he m old was m ove about during cast ing, and m ay also reveal dam ages and repairs not ot herwise apparent .
I nfrared reflect ography reveals carbon cont aining m at erials and ot herw ise " invisible" m edium . Carbon m edia hidden under ret ouching, dirt , or ot her m edia can be seen, revealing underdraw ings or pent im ent i ( lit er ally changes in t hought ) , or render ot her m edia invisible, such as bist re inks. I nfrared illum inat ion is especially useful w it h som e drawing m edia. I t can reveal covered signat ures, or erased pencil and ink, or abraded or faded drawings. I t can even penet rat e paint layers t o show prim at ura, or prelim inary draw ings.
Ra diogr a ph y : Radiography, using X- rays or m ore sensit ive bet a- and xero- rays, reveals changes in elem ent al densit y, so t hat t he physical st ruct ure of an obj ect m ay be art iculat ed t o show different layers, addit ions, elem ent s, et c. For bet a
radiography, t he paper obj ect is placed bet ween a radioact ive plat e and a piece of film for about 30 m inut es. The film is t hen developed and produces a negat ive sim ilar t o an x- ray. This can provide docum ent at ion of w at erm arks, m old
charact erist ics and ot her relat ive densit ies of t he paper. Xero- radiography is m ore powerful for denser papers and can som et im es reveal layers of papers.
M a gn ifica t ion : I n addit ion t o illum inat ion, m agnificat ion is a useful and relat ively sim ple m eans of exam ining an obj ect . A m agnifying glass can oft en help t o ident ify inclusions in paper or t he t ype of m edia. However, som et im es m uch higher
m agnificat ion is required.
St ereoscopic m icroscopes equipped wit h cool t em perat ure fiber opt ic raking light and ring can clarify t he nat ure of m edia by revealing t he size and shape of part icles, t he locat ion of t he m edia ( whet her it rest s above, on t op of or w it hin t he surface fibers) , t he layers of m edia or coat ings, t he t ype of det erior at ion ( such as live m old) , and t he ext ent of dam age, ret ouching or repairs.
A st age m icroscope wit h polarized light can m agnify sam ples m ore t han 100 t im es. Special feat ures of t his t ype of m icroscope can aid in t he ident ificat ion of an unknow n com ponent not only by m agnifying t heir feat ures, but also by allowing m easurem ent of t he opt ical propert ies of cryst als, such as refract ive index, ext inct ion, and
birefrengence. When carefully select ed, sam ples m ay provide inform at ion w hich is not only approxim at ely qualit at ive ( i.e. what is present ) , but also quant it at ive ( i.e. how m uch is present ) . Thin sect ions of obj ect s can also be m ore closely exam ined, and layers ident ified, by t his t echnique. Oft en a st age m icroscope is used in
conj unct ion w it h m icrochem ical t est s. For t his, t he sam ple is exposed t o various chem ical reagent s or solut ions w hich have a known react ion w it h specific m at erials. For inst ance, ident ificat ion of fiber t ypes can be furt her confirm by not ing t he colors t hey t urn when exposed t o cert ain st aining solut ions.
Ele m e n t a l Ana lysis: There are m any form s of qualit at ive and quant it at ive
inst rum ent al analyt ical devices for ident ifying bot h organic and inorganic elem ent , such as SEM elem ent al dispersive spect roscopy ( EDS) , Fourier- Transform - I R spect roscopy ( FT- I R) , Gas Chrom at ograph Mass Spect roscopy ( GCMS) , Thin- Layer Chrom ot ography ( TLC) , X- Ray Diffract ion ( XRD) and X- Ray Fluorescence ( XRF) . Follow ing various m eans of int eract ing w it h elem ent s, a m easurem ent or graph is creat ed t hat serves as a fingerprint of t he unknown com ponent t o be m at ched up wit h t hat of a known m at erial.
Pr ope r t ie s M e a sur e m e n t s: The chem ical and physical propert ies of m at erials change upon exposure t o oxidat ive, hydrolyt ic or m echanical forces. Propert ies t hat can be m easured and charact erized include color, gloss, opacit y, st rengt h, acidit y and degree of polym erizat ion, am ong ot her t hings. Depending on t he hist ory of exposure or use of m at erials, such changes m ay be predict able, or t hey m ay be accelerat ed or anom alous. For exam ple, t he rat es of det eriorat ion from t herm al or phot o oxidat ion can be ext rapolat ed from art ificial aging st udies using aging ovens and weat her- o- m et ers.
Dat ing a paper obj ect conclusively is next t o im possible. There are several t echniques for dat ing organic m at erials, such as radiocarbon dat ing,
paper. As indicat ed at t he st art of t his sect ion, t he best result s can com e from collaborat iv e curat orial effort s.
BI BLI OGRAPH Y
Bruyn, J. " The Concept of School," Jaffé, H.L.C. et al, edit ors. Aut hent icat ion in t he Visual Art s, Am st erdam , l979, pp. 1- 25.
Chat elain, Jean. Le Problem s des Faux en Mat iere Art ist ique. Et udes Sect eur Cult urel. 1979.
De Forest , P.R. et al. " Quest ioned Docum ent Exam inat ion," Forensic Science: An I nt roduct ion t o Crim inalist ics. McGraw- Hill, 1983. pp. 360- 382.
Denier van der Gon, J.J. " Spont aneit y in Mot or Expression," Jaffé, H.L.C. et al, edit ors. Aut hent icat ion in t he Visual Art s, Am st erdam , l979, pp. 93- 102.
Fay, S. et al. Hoax: The I nside St ory of t he Howard Hughes- Clifford I rving Affair, Viking Press, N.Y., l972.
Feller, R.L. " The Chem ist as Det ect ive: The t echnical Exam inat ion of Museum Obj ect s," The I ndicat or, Dec. 1959. pp. 20- 28.
Flem ing, S.J. " An evaluat ion of Physico- chem ical Approaches t o Aut hent icat ion," Jaffé, H.L.C. et al, edit ors. Aut hent icat ion in t he Visual Art s, Am st erdam , l979, pp. 103- 134.
Hanna, Georgia A. " Art Forgery: The Role of t he Docum ent Exam iner," Journal of Forensic Sciences, Vol. 37, No. 4, July 1992, pp. 1096- 1114.
Harrison, W.R. Suspect Docum ent s, Praeger, N.Y., l958.
Hughes, Robert . " Brilliant , But Not For Real," Tim e Magazine, May 7, 1990, pp. 118-119.
- - - . " Sold," Tim e Magazine, Novem ber 27, 1989, pp. 60- 65. Kurz, Ot t o. Fakes, Dover Publicat ions, New York, 1964 ( ?) .
McCrone, W. " The Vinland Map," Analyt ical Chem ist ry, Vol. 60, No. 10, May 15, l988, pp. 1009- 1019.
Naifeh, S. et al. The Morm on Murders, N.Y. l988.
New m an, R. " Aut hent icat ing your Collect ions," Caring for Your Collect ions, Abram s, New York, 1992, pp. 172- 180.
Osborn, A.S. Quest ioned Docum ent s, Boyd Print ing Co., N.Y., l946.
Perrig. A. " Aut hent icit y Problem s w it h Michelangelo: The Draw ings on t he Louvre sheet No. 685," Jaffé, H.L.C. et al, edit ors. Aut hent icat ion in t he Visual Art s, Am st erdam , l979, pp. 27- 54.
Rendell, Kennet h W. " The Det ect ion of Forgeries," Aut ographs and Manuscript s: A Collect or's Guide, Schribner's, N.Y., l978. Berkeley, E., edit or, pp. 73- 91.
Rendell, Kennet h W. " Fam ous Forgers: Their Successes and Downfalls," Aut ographs and Manuscript s: A Collect or's Guide, Schribner's, N.Y., l978. Berkeley, E., edit or, pp. 93- 99.
Wert hm ann, B. et al. " Nat urw issenschaft liche Aspekt e der Echt heit spruefung der songenannt en " Hit ler- Tagebuecher," Malt echnik- Rest auro, Vol. 90, No. 94, l984, pp. 65- 72.
ENDNOTES:
1. For lit erat ure on t hese cases, see Rendell. For t he Hughes " aut obiography" , see Fay. For Hit ler's " diaries" , see Wert hm ann. For t he Morm on fakes, see Naifeh.
2. For analyt ical t echniques, see Newm an.
3. For lit erat ure on st ylist ic analysis, see Konrad Oberhuber; Rendell.
4. For inform at ion on t he hist ory of paper m aking, see Dard Hunt er; John Krill. 5. To recap: what one should know about a paper support in order t o ascert ain it s qualit y or presence of inherent vice w hich is or m ay be a problem :
o t he fiber direct ion - it influences curl, st rain
o whet her t he fibers are long or short - influences fold endurance, st rengt h o whet her t he paper has been bleached - influences st rengt h and color o w het her t he paper is acid - m igrat es t o ot her it em s; discolors
o w het her it has m any im purit ies - sensit ive t o hum idit y & light o w het her it is coat ed or not - m akes it sensit ive t o m oist ure 6. For inform at ion on t he hist ory of m edia, see t he following foot not es. 7. East lake, C.L., Met hods and Mat erials of Paint ing of t he Great Schools and Mast ers, Vol. 1, Dover Publicat ions, I nc. New York, 1960, p. 151.
approach t o t he inst rum ent al analysis of nat ural finishes and binding m edia," Preprint s, Am erican I nst it ut e for Conservat ion, Washingt on D.C., 1988, pp. 67- 83; Burachinsky, B.V. " Print ing I nk," McGraw - Hill Encyclopedia of Science and
Technology, Vol. 7, New York, 1977, pp.123- 128.
9. For t radit ional m edia, see Cohn, M. B., Wash and Gouache, The Cent er for Conservat ion and Technical St udies, Fogg Art Museum , Cam bridge, MA, 1977;
