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8/10/2019 curatarea_monedelor_2

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COIN CHEMISTRY and CLEANING

Safety First!

DO Understand the materials you are working with

DO Procure a Material Safety Data Sheet for the chemicals you work with. Alwaysunderstand the hazards of each chemical.

DO NOT Mi acids and !ases.

"#$AN%N&' Don(t do it)

NOT$' Most attem*ts at coin cleaning ruin a coin(s condition and +alue. Unless you are+ery familiar with coin *roduction techni,ues- metallurgy and wet chemistry- you shouldcom*letely a+oid cleaning your coin. "leaned coins essentially !ecome damaged or

altered coins and ustify much less demand from collectors- not ust those ali+e today-!ut those in the net generations. An altruistic coin collector thinks not ust of theimmediate enoyment of the coin- !ut the education and enoyment of the coin o+er thenet few hundred years. /e are skin and !ones- destined for a few short decades.Metal coins might stick around for a few thousand more years...

Many new collectors attem*t coin cleaning with good intentions !ut *oor knowledge andtechni,ue. Ty*ical coin cleaning attem*ts include use of im*ro*er or harsh cleansersnot meant for that *articular coins chemistry or the *hysical wi*ing- cleansing- ru!!ingor scru!!ing of the coin face which disru*ts and alters the coin(s natural surface- *atinaor toning. Often seen undesira!le results include *its- unnatural fields or de+ices- *ock

marks- s*ots- scratches or corrosion on the coin.

/hen in dou!t 0 lea+e it out) Unless you are ,uite certain what the end result ofcleaning that *articular coin will !e- de+elo*ed through hard0earned e*erience or study1and likely a few ruined coins in the *rocess)2- suggest you lea+e the coin in its currentunmolested state until such time you are a!le to consult a more knowledgea!le coincurator. Until that time- your !est course of action is *ro!a!ly no action 0 lea+e the coinas is in the condition that first attracted you to it.

Those who can com*etently restore a coin do not clean the coin3 rather they curate thecoin. Think of the great Dutch master *aintings. They are restored or curated from a

damaged or dirty *osition to one more resem!ling the *hysical state ehi!ited when the*ainting was new. "leaning merely alters the surface of a *iece of art through- e+en ifim*erce*ti!le at first- damaging *hysical and chemical alteration.

4red 5einfeld- in his !ook' How to Build a Coin Collection.5e+ised 16th2 edition- sums it u*nicely'

"Since the results of cleaning cannot be accurately foreseen, and since the experts evendisagree on the advisability of cleaning, it is best to refrain".


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"leaning' %f you must do it...

%4 17when)2 you decide to ignore our sage counsel and commence on your home coinchemistry e*eriment in the mother(s8wife(s kitchen sink or o+en- a few to*ic0ti*s thatfollow may *ro+e useful. /hen starting out an Use low +alue common and well

circulated coins

De!ris and Dirt

Do not use a stick- rose thorn or tooth*ick to remo+e grease- grime- dirt- or other+erdigris from a coin surface. 9ou are likely to scratch the coin. The material youremo+e will also lea+e !ehind a *ortion of the coin surface that looks different than therest of the surface 0 *ro+iding an unwanted distraction. Ty*ical dirt that collects in acoins surface de+ices can sometimes !e satisfactorily remo+ed !y laying a film of:aseline with a cotton swa! or ;0Ti* or very fineco**er !rush or a rose thorn followed!y a gentle da!!ing- not ru!!ing- of the coin surface with a dedicated 1one use only2

+ery soft and lint free 1electrostatic2 cloth. Soaking a coin o+ernight 1or longer2 in oli+eoil or warm water or a *otatoes or coca cola is another fairly innocuous cleaning methodfor minor dirt adheringto a coin. &enerally- you are trying to counteract the conditionsthat fouled the coin surface. 4or instance- had !asic soil conditions created the issue-counteracting with acid treatment 1coca cola- muriatic acid2 may work3 or not. Do notuse any of these ti*s on a coin that holds high numismatic +alue. Unless you are !othtrained and e*erienced- DO NOT use acid0!ase chemistry to make your coins look*rettier such as use of' !aking soda- lye- *otash- clay- +inegar- acetic acid- muriaticacid- sulfuric acid- coca cola etc. since these methods will destroy the numismatic +alueof your coin and *otentially cause you health or safety *ro!lems.

Dust


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acetone !ath must !e done right. Use high ,uality Acetone 1not the stuff you will find atTarget or /almart2. See Acetone !elow.

Proof "oins

Ne+er touch any surface of a *roof coin. These finishes command a high numismatic*remium. Any ru!!ing- *olishing or other touching will ruin the surface.

Toning

"ollectors attached a *remium for attracti+ely toned coins. 5egretta!ly- this *remiumhas con+inced unscru*ulous indi+iduals to doctor u* coins with artificial toning for theirown !enefit. Also- some natural toning is sim*ly unattracti+e. 4or this category coin- a,uick (di*( may remo+e the ugly tone. Additionally- *rofessionals that ha+e *roof coinswith (haze( in the mirrored field will also di* the coins. $ssentially- di*s are sol+ents thatremo+e a +ery thin layer of steel. As such- the coin is essentially now a cleaned coin.

Ne+ertheless- a large *ercentage of the coin industry considers (di**ing( to !e the only(market acce*ta!le( cleaning method. All others are considered +er!oten- and theirdetection !y the Third Party &raders ty*ically will result in the coin !eing returned in a(!ody !ag(' an un0certifia!le coin.

Coin Chemistry at the Coin Mine

Introduction

/hen a sil+er coin is newly minted- the force of the *ress forces the sil+er into thedetails of the die and collar- creating a ?fresh? sil+er surface. As soon as it lea+es the

dies- the coin is e*osed to different en+ironments. %f hermetically sealed- for eam*lein inert *lastic and left in a +ery sta!le *lace- such as a tem*erature and humiditycontrolled +ault containing inert gas 1or +acuum2- it will theoretically stay !right andwhite fore+er- since it will ha+e no elements to react with.Once the coin lea+es the mint- it undergoes +arious chemical and *hysical reactionswhen e*osed to the atmos*here. Some of the atmos*heric com*ounds that can reactwith metals include "ar!onyl Sulfide 1"OS2- @ydrogen "hloride 1@"%2- @ydrogen Sulfide1@S2 and Sulfur Dioide 1SO2. These gasses form naturally and occur as !y*roductsfrom decom*osition or natural or synthetic materials.

Physical *rocesses include a!rasion corrosion- rust- s*otting- mold and mildew- ande*osure to non0gaseous en+ironmental factors such as heat and sunlight. Some*rocesses are !oth chemical and *hysical- such as ru!!ing a coin with ones(s thum! orforefinger. This ru!!ing *roduces a *hysical effect !y softening the details of the coinsstrike to a +ery small degree and also a chemical *rocess that occurs when human fatsand oils interact with the metallic surface of the coin.


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Oidation is ust one chemical *rocess that occurs when a metal is e*osed to a gas.$arly chemists thought that oidation occurred when a metal was e*osed to oygen1and hence the name oidation2 although oidation in the chemical +ernacular refers tothe *rocess where a com*ound undergoes a reaction that remo+es an electron.

4or our *ur*oses- coin oidation de+elo*s an oide layer on the coins surface 1and alsoon the su!surface2. $lectrolysis remo+es the surface oide layer 1or other !y0*roductsof oidation such as car!ide- hydride- halide- nitride and sulfide2 . "ommerciallya+aila!le di*s such as


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means there are ecess hydrogen ions- or *rotons- in solution. Protons in solution will!ond with water 1@O2 to form hydronium ions 1@EOF2.

Solutions may eist with charges !ut gasses do not- ece*t under unusual conditionswhere they are called *lasmas. %n some instances- hydrogen ions 1*rotons2 will !ond to

another ion other than water. 4or instance- when a !asic 1*@ o+er 6.G2 solution iscom!ined with the acidic solution- the *roton will !ond with an hydroyl ion 1O@02eisting in the !asic solution. @ydroyls and hydrogen com!ine to form water. Now- ifwe add a metal to the solution- the solution might stri* an electron to form hydrogen !ycom!ining with *rotons in solution 1hydrogen ions2. This metal ion might not !e sta!leand search for another *roton to !ecome neutral and thence dro* out of the solution asa solid *reci*itate. One must !e +ery careful when forming metal *reci*itates insolution since metal salts could !e *roduced. $am*les of metal salts that are*roduced through coin chemistry are gold chloride 1hydrochlorauric acid2 and sil+ernitrate. Metal salts are used in a wide +ariety of industrial a**lications. 4or instance-Harium "ar!onate is a rodenticide. Although metal salts can !e +ery dangerous they

also ha+e many hel*ful attri!utes and find wide a**lications such as *rinting and*hotogra*hy.

"o**er- like sil+er- is a grou* CC transition metals. @owe+er co**er has significantlydifferent reduction *otential and therefore will react with many more solutions than willco**er. That is why co**er coins ty*ically ehi!it much more en+ironmental damagethan sil+er coins such as corrosion- *itting and the (green gunk(.

4or many collectors one of the features that adds eye a**eal is the toning- or addition ofcolor to the coins surface- o+er time.

The color ehi!ited !y a coin is related to the thickness of the thin oide layer on thecoin surface and the wa+elength of light that is reflected off the surface. Some of thelight is reflects off of oide surface !ack to the +iewers eye- hence light is seen. Theremaining *ortion of the light *enetrates the the oide layer to the *hysical face of thecoin and then reflect !ack to the +iewers eye. These different distance that the lighttra+els is enough to create +arious hues +isi!le to the naked eye. Some light may onlymake it *art way through the oide layer !efore reflecting !ack. Sometimes the +ariouswa+elengths com!ine as either constructi+e or destructi+e forces to either reinforce orcancel out certain colors. These distances of the oide layer through which lightwa+elengths *ass are so small that they are measure in angstroms- or nanometers 1CGangstroms2. :isi!le wa+elengths with +arying fre,uencies *roduce +arious colors.

Different wa+elengths re*resent different s*ectrums of the energy !and. The length ofthe wa+e- the distance !etween two *eaks formed in a sine wa+e +ia oscillation- is usedto define the energy of the wa+elength. Only a *ortion of the energy !and is +isi!le aslight to the human eye. $nergy wa+elengths that oscillate slower than +isi!le lighttoward the red end of the s*ectrum include infra0red and radio wa+es. /a+es !eyondthe other end of the s*ectrum include ultra+iolet light- and radiation wa+es such as I0rays and gamma0rays. 5adio wa+elengths are measured as the num!er of cycles the


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wa+elengths com*lete o+er a fied *eriod of time 1hertz2- and are e*erienced whenhitting the human eardrum as sound. $ach wa+elength is a se*arate sound. 4oream*le- fre,uencies that resonate at JJG cycles *er second are defined as the musicalnote A.

There are ways to determine the actual metallic com*osition- e+en of layered cladcoins- using S$M0$DI testing.

See more on Toning.

Use of some treatment- or any 0 de*ending u*on your *ersonal integrity and*rofessional mettle 0 may trigger the re,uirement to *ro+ide notice that your coin wasworked on or otherwise modified3 that the coin no longer has original surfaces.

"oin "leaning and "uration 5eference

A!sor*tion 0

Acetone 0CGG> acetone can !e a +alua!le tool in the right hands for the right o!. Theright o! may include detection of fake mint marks that ha+e !een added with e*oy orin cleaning the surface of the coin for haze or recent finger*rints. Acetone is a sol+ent-not an acid- so it does not remo+e metal from the coin. @owe+er- it can lea+e a !rownishlooking haze- es*ecially along the rim- when not rinsed *ro*erly. That is- after anacetone !ath 0 which should only take a cou*le seconds- the coin must then !e rinsedimmediately in distilled water. Distilled water is essential !ecause we want none of theim*urities- such as can !e found in natural water- to remain on the surface of the coin 0after all- that is the reason we di**ed it in the first *lace. Although certain +ery *ure

alcohols can also !e used as a *ost0acetone !ath- this ty*e of chemistry is morecom*licated3 so kee* it sim*le with distilled water.

Use a glass sealed container 1*refera!ly with a wide mouth so you can reach in the arto get the coin !ack out !y hand2. 9ou could fold u* a na*kin and line the !ottom of the

ar which will *re+ent the nickel from getting nicked !y friction against the glass side ofthe ar.

The coin should then !e air dried 1not forced air23 or- after the !ath- *at 1not ru!- notwi*e2 the coin dry using tissue *a*er.

Di**ing in acetone is done to remo+e *lastic from a coin. Ty*es of *lastic such as P:"may form residue on a coin from im*ro*er storage or en+ironmental conditions. Sinceacetone is an organic sol+ent- it will only react with *lastic 1or other organics2 and NOTthe coin. Use of CGG> high grade acetone is essential3 it(s stored in metal *int or ,uarttins in the *aint section at the hardware store- not at /almart or Target.


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This site contains a fair amount of information on co**er chemistry'htt*'88www.dig!i!le.org8restoration.html

"uration 0

"yanide 0"yanide has !een used +ery effecti+ely to mine and treat metals. 9ears agoco**ersmiths treated co**er with *otassium cyanide. Potassium cyanide has also!een used !y coin counterfeiters in attem*ts to add a matte0like finish to cu*ro0nickelcoins. "urrent uses *rimarily occur in the metal etching and *lating !usiness sincecyanide in com!ination with strong acids can kee* *recious metals in solution.

/orking with cyanide can !e *erilous. "yanide salts are *articularly dangerous. 4oream*le- sodium cyanide is used in the gas cham!er !ecause when sodium cyanide- orany other cyanide salt is mied with a strong acid- hydrogen cyanide is released. 4orthis reason cyanide salts are also *oisonous when ingested- !ecause the acid in yourstomach will also li!erate hydrogen cyanide.

Deller(s "o**er "leaner 0A**ears to !e *etroleum elly and sulfur *owder.

$lecto*lating 0$lectro*lating is the de*osition of a metallic coating onto an o!ect !y*utting a negati+e charge onto the o!ect and immersing it into a solution which containsa salt of the metal to !e de*osited. The metallic ions of the salt carry a *ositi+e chargeand are attracted to the *art. /hen they reach it- the negati+ely charged *art *ro+idesthe electrons to reduce the *ositi+ely charged ions to metallic form.

$lectrolysis 0 4or our *ur*oses- coin oidation de+elo*s an oide layer on the coinssurface 1and also on the su!surface2. $lectrolysis remo+es the surface oide layer.

"ommercially a+aila!le di*s such as


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$lectrowinning 04rom 4inishing.com 1htt*'88www.finishing.com8fa,s8howworks.html2

eBest 0A chemical di*3 likely a diluted sol+ent. Not recommended whatsoe+er.

&old 0


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Of course- natural !eauties do not need the knife)

Solder 0 4or remo+ing solder from a coin used as old ewelry- consider using a co**er!raid to *roduce flu that will then a!sor! the old solder.

Tri Sodium Phos*hate 0

Toning 0Toned coins show +arious colors reflected in their fields or de+ices as o**osedto an a**earance uniform in color. Heware of artificial toning gained through nefariousa**lication of heat or chemicals to *roduce toning. This gentleman *ro+ides a +erygood write u* on the science of toning'

htt*'88www.i+yleaguecoin.com8*ages868inde.htm

Ultrasonic "leaners 0These mechanical de+ices use sound wa+es to mechanically+i!rate soil and grime off of surfaces. They do work !ut can ha+e unintentionalconse,uences- such as lea+ing a dra! and *ale surface a**earance on your coin. Onething to consider is *lacing a coin at the !ottom of the container on to* of a small *ieceof gauze. This way- when the ultrasonic cleaner is turned n the coins will +i!rate againstthe gauze surface- not ht glass surface. This will reduce the large num!er of micromarks on the coin *ick0u* *oints 1the raised features23 these micro marks com!ine tolook like *olish 0 which detracts from the coin a**earance.

Iylene 0"an !e used to clean light corrosion on co**er- using a fine horsehair !rush for

a**lication. Ortho and Meta Iylene are !oth sus*ected carcinogens so use in a well+entilated area.

Qestion Someone "a#e me a $n%h of &ffa'o Ni%(e's that 'oo(ed 'i(e they)ere %'eaned )ith Ta$as%o Sa%e* +hy did they do that, and )hat sho'd I do toma(e them 'oo( more natra'-

Ans)er

He used Tabasco b.c. he only partially knew what he was doing and b.c.:

1)

Contains vinegar, a weak acid

2) Contains capsaicin andor other astringents

!oth acids and astringents are used to "etch# $etal. In the case o% the bu%%alo nickel people use

acids to bring out the date, known as acid dates.
http://www.ivyleaguecoin.com/pages/7/index.htmhttp://www.ivyleaguecoin.com/pages/7/index.htm


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To understand how to re$ove an ite$, you $ust understand the che$ical properties. The %irst

place to go is the &'(' %or each:

http:www.skcinc.co$instructions*+*.pd%

http:www.aversiontech.co$capsaicin.ht$l

The way to neutrali-e an acid is to either dilute using neutral) or $odi%y using basicalkali).

/sing $alt vinegar won#t work that e%%iciently, since you are using a vinegar to work on a

vinegar. 0ow, that is %ine i% you are using a stronger acid to re$ove a weaker acid, but you still

need to neutrali-e and re$ove the acid, which reuires neutral or base.

'o, you need to conduct a physical re$oval process, such as electrolysis, or a che$icalacidbase che$ical reaction. I% you aren#t that %a$iliar with che$istry probably not sa%e %or you

to do your own acidbase che$istry.

&y suggestion is soap and water, as you said, and arti%icially retone by storing %or a long ti$e 3

with added heat 3 against sul%ur paper.

!ut, 4ust %or kicks. These bu%%s are only worth several cents each 3 no $onetary reason to

%urther $ess with the coin.

5ood luck. !e sa%e. Have 6un.

Sor%es

"oin Preser+ation @and!ook."harles 4rank. Pu!lished !y "oinguard %ndustries. C=J.@ardco+er. 4ine. :ery minor sulfur staining inside !ack co+er from where old *a*er wasstored3 small old *rice written on inside co+er. @ard !ook to find- im*ortant referencework. 5eference.

Methods of "hemical and Metallurgical %n+estigation of Ancient "oins 1edited !y $. T.@all and D. M. Metcalf- C=62-

FORGERIES

"o**er

&old


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Co..er s.ots Since US gold coins are a cu8au alloy- many ha+e a co**er s*ot 0areas of co**er toning. #ook for these as indication of authenticity.

Cast For"eriesMost forgeries are cast forgeries- unso*histicated and easily 1usually2detected and therefore the mot common ty*e of coin fraud.

"ast forgeries ty*ically ha+e !u!!les. 5ealize that a cast forgery- e+en a high ,ualityforgery with ust minimal !u!!les and +ery good diagnostic and design detail- will likely!e slightly undersized and underweight. /eight is a maor determining factor forauthenticity. Die0struck counterfeits are the most common ty*e of gold counterfeit.

The most e*erienced coins dealers that % ha+e done !usiness with ha+e re*orted thathe least counterfeited gold !ullion coin is the US &old $agle followed !y the "anadianMa*le #eaf and then the SA Kreuggerand. The most commonly counterfeited gold!ullion coins are the Hritish So+ereigns 1die0struck2 and Middle $astern coins includingSaudi &uineas- and many Turkish and %ranian gold coins.

The first *lace to !egin when ensuring authenticity of gold !ullion is to check size-weight and mass. A 4isch detector *ro+es most +alua!le here as it measures !oth massand size 1called dimensions for coins2 3 use the Two05and 4isch to authenticateso+ereigns.

Unfortunately- one thing we need to start looking out for are gold coins that are diestam*ed. The core is tungsten core and the *lating is gold. These can !e machined tothe right s*ecs and therefore etremely difficult to detect !y density or rotational inertia.@owe+er microsco*ic analysis- ultrasound and I0ray with thermal conducti+ity may workat detection methods. Tungsten has historically !een !oth and e*ensi+e and difficult to

turn into coin0worthy *lanchets. As the "hinese increase their so*histication andmastery of machine and milling techni,ues- this will increasingly !ecome a more +eing*ro!lem.

One way to side ste* the issue- and another reason to !uy smaller denomination coins-is to a+oid one0ounce coins in fa+or of half or ,uarter0ounce !ullion coins.

$lectro*lating"leaning in its myriad formsDi**ing

Artificial tones

Hust augmentation$agle feather im*lantsMint mark remo+al and addition4lat out date alteration- and5eha!ilitation- restoration- and other of the ilk.

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