american hand book of the daguerreotype-第23部分

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ng；　to　be　able　to　procure　an　even　perfect　surface；　from　the　fact　that　a　pure　surface　of　silver　could　scarcely　be　obtained；　the　manufacturers　deeming　it　too　much　trouble　to　prepare　silver　plated　copper　with　pure　silver　the　result　was；　that　in　attempting　to　polish　perfectly　such　plated　metal　as　could　be　procured；　the　plates　would　become　cloudy；　or　colored　in　spots；　from　the　fact　of　having　more　or　less　alloy；　according　as　more　or　less　of　the　silver　surface　was　removed　in　polishing　the　plate　fit　for　an　impression。　To　explain　more　clearly；　it　was　the　practice　of　most　silver　platers　to　use　an　alloy　for　silver…plating。　In　the　reduction　of　the　ingot　to　sheet　metal；　annealing　has　to　be　resorted　to；　and　acid　pickles　to　remove　oxides；　etc。　　The　number　of　times　the　plated　metal　is　exposed　to　heat　and　acid　in　its　reduction　to　the　required　thickness；　produces　a　surface　of　pure　silver。　The　most　of　this　surface　is；　however；　so　rough　as　to　be　with　difficulty　polished；　without　in　places　removing　entirely　this　pellicle　of　pure　metal；　and　exposing　a　polished　surface　of　the　alloy　used　in　plating。　　Whenever　such　metal　was　used；　very　unsightly　stains　or　spots　frequently　disfigured　the　portraits。　The　portrait；　or　portion　of　it；　developed　upon　the　pure　silver；　being　much　lighter　or　whiter　than　that　developed　upon　the　alloy；　it　therefore　appeared　that　the　purer　the　silver；　the　more　sensitive　the　plate　became。　　Accordingly；　we　directed　Messrs。　Scovills；　of　Connecticut；　to　prepare　a　roll　of　silver…plated　metal；　with　pure　silver；　it　fortunately　proved　to　be　a　good　article；　but；　unfortunately；　a　pound　of　this　metal　（early　in　1840）　cost　the　round　sum　of　9。　Like　descriptions　of　metal；　the　same　gentlemen　would　be　glad　to　furnish；　at　this　time；　for　4。　Soon　after　this；　some　samples　of　English　plated　metal；　of　a　very　superior　quality；　came　to　our　possession；　and　relieved　us　from　the　toil　of　making　and　plating　one　plate　at　a　time；　an　expedient　we　were　compelled　to　resort　to；　to　command　material　to　meet　the　pressing　demands　for　portraits。

Having　it　now　in　our　power　to　obtain　good　plated　metal；　a　more　rapid　mode　of　polishing　than　that　recommended　by　Daguerre　was　attempted　as　follows：

This　metal　was　cut　to　the　desired　size；　and　having　a　pair　of　〃hand　rolls〃　at　hand；　each　plate；　with　its　silvered　side　placed　next　to　the　highly　polished　surface　of　a　steel　die；　was　passed　and　repassed　through　the　rolls　many　times；　by　which　process　a　very　smooth；　perfect　surface　was　obtained。　The　plates　were　then　annealed；　and　a　number　of　plates　thus　prepared　were　fastened　to　the　bottom　of　a　box　a　few　inches　deep　a　foot　wide；　and　eighteen　inches　long；　this　box　was　placed　upon　a　table　and　attached　to　a　rod　connected　to　the　face　plate　of　a　lathe；　a　few　inches　from　its　centre；　so　as　to　give　the　box　a　reciprocating　motion。　　A　quantity　of　emery　was　now　strewn　over　the　plates；　and　the　lathe　set　in　motion。　The　action　produced　wag　a　friction　or　rubbing　of　the　emery　over　the　surface　of　the　plates。

When　continued　for　some　time；　a　greyish　polish　was　the　result。　Linseed；　when　used　in　the　same　manner；　gave　us　better　hope　of　success；　and　the　next　step　resorted　to　was　to　build　a　wheel　and　suspend　it　after　the　manner　of　a　grindstone。　The　plates　being　secured　to　the　inner　side　of　the　wheel　or　case；　and　as　this　case　revolved；　the　seeds　would　constantly　keep　to　the　lower　level；　and　their　sliding　over　the　surface　of　the　plates　would　polish　or　burnish　their　surfaces。　　This；　with　the　former；　was　soon　abandoned；　rounded　shots　of　silver　placed　in　the　same　wheel　were　found　not　to　perform　the　polishing　so　well　as　linseed。　Buff…wheels　of　leather　with　rotten…stone　and　oil；　proved　to　be　far　superior　to　all　other　contrivances；　and；　subsequently；　at　the　suggestion　of　Professor　Draper；　velvet　was　used　in　lieu　of　buff　leather；　and　soon　superseded　all　other　substances；　both　for　lathe　and　hand…buffs；　and　I　would　add；　for　the　benefit　of　new　beginners　that　those　who　are　familiar　with　its　use；　prefer　cotton　velvet。　The　only　requisite　necessary　is；　that　the　buffs　made　of　cotton　velvet　should　be　kept　dry　and　warm。

The　greater　number　of　operators；　with　whose　practice　I　am　familiar；　use；　for　polishing　plates；　prepared　tripoli；　imported　from　France；　or　Browne's　rotten…stone。　The　former　of　these　articles　is　very　objectionable；　inasmuch　as　there　is　no　positive　certainty　of　being　enabled　to　procure　or　make　the　article　of　uniform　gritthe　nature　of　the　substance　rendering；　it　impossible　to　reduce　it　to　varying　degrees　of　evenness；　by　the　well　known　process　of　washing；　for　that　purpose；　and　the　burning　of　rotten…stone　changes　its　chemical　nature　somewhat；　at　the　same　time　rendering；　this　invaluable　article　harsh　and　gritty。　And　especially；　no　reliance　can　be　placed　upon　burned　rotten　stone　if　purchased　from　those　who　do　not　give　very　great　attention　and　care　to　its　preparation；　and　the　same　remarks　apply　to　rouge。

The　best　article　for　polishing　Daguerreotype　plates　is　rotten…stone；　such　as　can　be　procured　in　any　town；　prepared　after　the　following　manner：　　Procure；　say　half　a　dozen　wide…mouthed　bottles；　of　suitable　dimensions；　numbering　each　from　one　to　six。　Put　into　No。　1　about　half　a　pound　of　rotten…stone。　and　nearly　fill　the　bottle　with　water。　　Then；　with　a　proper　stick　or　spatule；　mix　well　the　rotten…stone　and　water；　after　which；　let　No。　1　rest　for；　say　one　minute；　then　carefully　pour　off　into　bottle　No。　2　（or；　what　would　be　better；　draw　off　by　a　syphon）　as　much　of　the　floating　particles　of　rotten…stone　as　is　suspended　in　the　water。　Again　fill　bottle　No。　1　with　water；　agitate　it　as　before；　and　decant　it　to　bottle　No。　2；　care　being　taken　to　draw　off　only　the　suspended　particles　of　rotten…stone。

When　a　sufficient　quantity　of　washings　from　bottle　No。　1　is　collected　into　bottle　No。　2；　a　similar　process　must　be　gone　through。　　as　above　stated；　for　No。　1；　the　difference　being　in　the　care　required；　and　in　the　time　allowed　between　the　stirring　or　mixing　the　rotten…stone　and　water。　The　floating　particles　of　rotten…stone；　after　four　minutes'　subsiding；　will　be　found　fine　enough　for　the　finest　Daguerreotype　polishing　required。

A　quantity　of　such　washings　may　be　collected　in　a　large　bottle；　and　allowed　to　stand　a　few　hours；　when　all　the　rotten…stone　will　have　settled。　　The　water　may　be　poured　off　and　the　rotten…stone　put　into　an　evaporating　dish；　and　while　being　dried；　must　be　constantly　stirred　to　obtain　an　impalpable　powder。

Further　washings　may　in　like　manner　be　resorted　to　for　finer　qualities　of　rotten…stone。　In　my　practice；　I　have　used　the　articles　at　two　and　four　minutes'　settling；　and　occasionally　have　prepared　it　after　standing　for　eight　minutes。　So　fine　a　quality　as　this；　however；　is　seldom　required。　In　using；　rotten…stone；　I　mix　with　it；　for　polishing；　fine　olive　oil；　until　I　obtain　a　thin　pasteand　the　best　of　all　methods　for　polishing　（well　planished）　Daguerreotype　plates；　is　one　like　that　used　for　glass　by　lens　polishers；　that　is；　by　using　a　disc　or　buff…wheel；　and　having；　a　suitable　holder　by　which　to　secure　the　plate；　and　then　by　pressing　the　plate　against　the　revolving　buff；　well　saturated　with　the　mixed　oil　and　rotten…stone；　a　very　good　surface　is　obtained。　A　quantity　of　plates　may　be　prepared　in　this　way；　and　all　the　adhering　oil；　etc。；　may　be　removed　by　a　clean　hand；　or　lathe　buff；　after　which　each　plate　must　be　heated　to　the　point　necessary　to　burn　off　the　remaining　oil　great　care　being　required　not　to　overheat　the　plate。　　A　very　slight　excess　of　temperature　will　at　once　destroy　all　the　polish　previously　obtained。　The　test　for　ascertaining　the　right　temperature　is　at　hand；　the　adhering　oil　will　be　driven　from　the　plate　in　the　form　of　smoke　when　the　right　temperature　is　reached。　　The　moment　the　smoke　ceases　to　rise　from　the　plate；　the　heat　must　he　removed；　and　the　plate　quickly　cooled　upon　a　piece　of　iron。

A　quantity　of　plates　thus　prepared　may　be　kept　on　hand　for　any　required　time；　and　the　labor　of　one　minute；　with　a　lathe　or　hand…buff　with　dry　charcoal；　or　rather；　prepared　lampblack；　will　perfectly　polish　the　surface　ready　for　indexing；　etc。　This　lampblack　also　requires　some　care　in　preparing。　Take　a　small…size　crucible；　properly　temper　it　by　a　slow　fire；　that　it　may　not　be　cracked　after　which；　fill　it　with　common　lampblack；　cover　it　over　with　a　piece　of　soap…stone；　and　again　replace　it　in　the　fire。　　Build　a　good　hard　coal　fire　around　it　continue　the　heat　for　two　or　three　hours；　being　careful　not　to　raise　the　cover　till　the　crucible　be　quite　cold。　　Pulverize　when　using　it。　It　is　very　desirable　to　keep　this　lampblack　dry　and　warm。　Some　operators　use　much　rouge　I　would　recommend　the　above　in　preference；　but　those　who　feel　that　they　cannot　dispense　with　the　use　of　rouge；　had　better　try　a　large　addition　of　prepared　lampblack　to　a　small　one　of　rouge；　as　this　latter　article；　unless　great　pains　be　taken　in　its　preparation；　will　adhere　and　work　itself　into　the　body　of　the　surface；　so　that　it　cannot　be　removed　therefrom；　and　I　have　seen　many　specimens　of　Daguerreotype　very　much　injured　in　effect　from　this　rouge　tint　disseminated　throughout　their　shaded　features；　at　the　same　time　that　the　whole　general　effect　of　such　pictures　is　that　of　a　want　of　life。　It　is　true　that　with　the　use　of　rouge　a　very　high　degree　of　polish　may　be　obtained；　but　probably　not　higher　than　can　be　produced　with　many　other　substances　of　a　less　objectionable　nature。

From　the　announcement　of　the　discovery　by　Daguerre　to　the　beginning　of　the　year　1840；　I　am　not　aware　of　any　attempt　to　lessen　the　time　for　the　action　of　an　image；　or　an　impression；　other　than　that　of　the　reflecting　camera　invented　by　Mr。　Wolcott。　　Early；　however；　in　1840；　Mr。　Wolcott　was　desirous　to　be　enabled　to　further　shorten　the　time　for　a　sitting；　and　having　some　knowledge　of　bromine　and　its　action；　by　request；　Dr。　Chilton　prepared　a　small　quantity；　but　Mr。　Wolcott　did　not　succeed　very　well　with　it；　he　having　invariably　used　too　much　in　combination　with　iodine　to　produce　that　sensitive　coating　now　well　known　to　the　profession。　Professor　Morse；　of　this　city；　Dr。　Goddard；　of　Philadelphia；　and　others；　in　the　years　1840　and　1841；　were　acquainted　with　the　use　of　bromine。　N。　Griffing；　of　this　city；　or　myself；　used　with　tolerable　success；　iodine　in　large　excess　to　nitric　acid　and　water；　a