the history and practice of the art of photography-第12章

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lities　are　possessed　to　an　eminent　degree　by　the　French　plates。

Having　already　enumerated　the　various　processesand　the　apparatus　necessary　for　the　manipulation；　I　will　here　give　a　list　of　the　chemicals　to　be　used；　and　then　proceed　to　explain　them　more　fully。　The　requisite　chemicals　are

　NITRIC　ACID；　　　　　　　　　　　　　ROUGE；　　DRY　IODINE；　　　　　　　　　　　　　　MERCURY；　　DRYING　POWDER；　　　　　　　　　　　HYPOSULPHITE　OF　SODA；　　CYANIDE　OF　POTASSIUM；　　　　CHLORIDE　OF　GOLD；　OR　　ROTTENSTONE；　　　　　　　　　　　　　HYPOSULPHITE　OF　GOLD。　　TRIPOLI；　　　　　　　　　　　　　　　　　CHLORIDE　OF　SILVER。　　CHLORIDE　OF　IODINE；　｝　their　compounds；　or　other　　BROMINE　　　　　　　　　　　　　｝　accelerating　mixtures。

FIRST　OPERATION。Cleaning　and　polishing　the　plate。　For　this　purpose　the　operator　will　require　the

Plate　Blocks；

Plate　Vice

Spirit　Lamp；

Polishing　Buffs；

Nitric　Acid；　diluted　in　fifteen　times　its　bulk　of　water

Galvanic　Battery；　to　galvanize　the　plate；　if　it　is　too　imperfect　to　be　used　without；　previous　cleaning　it；　as　directed　in　the　last　chapter。

Rottenstone；

Tripoli；　which　is　too　often　dispensed　with。

Rouge；　or　lampblackthe　first　being　most　preferable。　The　English　operators　mix　the　two　together。

Prepared　cotton　Wool；　or　Canton　flannel。　　If　the　first　is　used；　it　should　be　excluded　from　the　dust；　as　it　is　not　so　easily　cleansed　as　the　latter。

The　plate　is　secured；　with　its　silver　side　upward；　to　the　block；　by　the　means　described　on　page　58having　previously　turned　the　edges　backward　all　around。　　The　amount　of　cleaning　a　plate　requires；　depends　upon　the　state　it　is　in。　　We　will　suppose　one　in　the　worst　condition；　dirty；　scratched；　and　full　of　mercury　spots；　all　of　which　imperfections　are　more　or　less　to　be　encountered。　The　mercury　spots　are　to　be　removed　by　burning　the　plate。　To　do　this　hold　the　plate　over　the　flame　of　a　spirit　lamp；　more　particularly　under　the　mercury　spots；　until　they；　assume　a　dull　appearance；　when　the　lamp　is　to　be　removed；　and　the　plate　allowed　to　cool；　after　which　it　is　attached　to　the　block。

Place　the　block　upon　the　swivle；　and　hold　it　firmly　with　the　left　hand；　take　a　small　knot　or　pellet　of　cotton；　or；　if　you　like　it　better；　a　small　piece　of　canton　flannelwet　it　with　a　little　diluted　nitric　acid；　then　sift　some　finely　prepared　rottenstoneDavie's；*　if　you　can　get　it　upon　it；　and　rub　it　over　the　plate　with　a　continual　circular　motion；　till　all　traces　of　the　dirt　and　scratches　are　removed；　then　wipe　off　the　rottenstone　with　a　clean　piece　of　cotton；　adopting；　as　before；　a　slight　circular　motion；　at　the　same　time　wiping　the　edges　of　the　plate。　Even　the　back　should　not　be　neglected；　but　throughly　cleansed　from　any　dirt　or　greasy　film　it　may　have　received　from　handling。

*　Sold　by　E。　Anthony。

When　this　is　thoroughly　accomplished；　mix　a　portion　of　your　tripoli　with　the　dilute　nitric　acid；　to　the　consistence　of　thick　cream。　Then　take　a　pellet　of　cotton　and　well　polish　the　plate　with　this　mixture；　in　the　same　manner　as　with　the　rottenstone。　　Continue　the　process　till；　on　removing　the　tripoli　with　a　clean　pellet；　the　plate　exhibits　a　clear；　smooth；　bright　surface；　free　from　all　spots；　or　scratches。　Any　remains　of　the　acid　on　the　plate　may　be　entirely　removed　By　sifting　on　it　a　little　Drying　powder；　and　then　wiping　it　carefully　off　with　a　fine　camels　hair　brush；　or　duster。　　The　finishing　polish　is　now　to　be　given。

For　this　purpose　the　rougeor　a　mixture　of　rouge　and　lamp…black；　in　the　proportion　of　one　part　of　the　former　to　seven　of　the　latteris　used。　It　should　be　kept　either　in　a　muslin　bag；　or　wide　mouth　bottle；　over　which　a　piece　of　muslin　is　tiedin　fact；　both　the　rottenstone　and　tripoli　should　be　preserved　from　the　dust　in　the　same　manner。　With　a　little　of　this　powder　spread　over　the　buffdescribed　on　page　53　the　plate　recieves　its　final　polish；　the　circular　motion　is　changed　for　a　straight　one　across　the　plate；　which；　if　intended　for　a　portrait；　should　be　buffed　the　narrow　way；　but　if；　for　a　landscape　or　view　of　a　house；　the　length　way　of　the　plate。

The　operation　of　cleaning　the　plate　at　first　appears　difficult　and　tedious；　and　many　have　been　deterred　from　attempting　this　interesting　art　on　that　account；　but；　in　reality；　it　is　more　simple　in　practice　than　in　description；　and　with　a　little　patience　and　observation；　all　difficulties　are　easily　overcome。　Great　care　must　be　taken　to　keep　the　buff　free　from　all　extraneous　matter；　and　perfectly　dry；　and　when　not　in　use　it　should　be　wrapped　up　in　tissue　paper；　or　placed　in　a　tight　box。

The　plate　should　be　buffed　immediately　before　the　sensitive　coating　is　given；　particles　of　dust　are　thus　effectually　removed；　the　temperature　of　the　plate　is　also　increased　by　the　friction；　and　the　required　tint　more　readily　obtained。

SECOND　OPERATION。Applying　the　sensative　coating。The　apparatus　and　chemicals　required；　are　an

Iodine　boxsee　fig。　14　page　53。

Bromine　boxsimilar　to　the　iodine　box　but　a　trifle　deeper。

Dry　Iodine。

Bromine；　or　a　compound　of　Bromine　and　Chloride　of　Iodine；　or　other　sensitive　mixture。

Most　of　our　best　operators　use　the　compound　Bromine　and　Chloride　of　Iodine。　　In　the　early　days　of　the　Daguerreotype；　Iodine　alone　was　used　in　preparing　the　plate；　and　although　it　still　plays　a　very　important　part；　other　preparations；　called　accelerating　liquids；　quickstuff；　&c。；　are　used；　and　the　discovery　of　which　has　alone　ensured　the　application　of　the　Daguerreotype　successfully　to　portrait　takingfor　when　first　introduced　among　us　it　took　from　five　to　ten　minutes　to　produce　a　tolerable　good　view；　while　now　but　the　fraction　of　a　minute　is　required　to　obtain　an　accurate　likeness。

To　iodize　the　plate　perfectly　it　must　be　placed　over　the　iodine　vapor　immediately　after　buffing。　　Scatter　from　a　sixteenth　to　the　eighth　of　an　ounce　of　dry　iodine　over　the　bottom　of　your　coating　box；　and　slightly　cover　it　with　cotton　wool。　　The　plate　is　then　dropped　into　the　frame　b；　fig。　12；　with　its　silvered　surface　downward；　and　thrust　under　the　lid　h。　　The　bright　surface　of　the　plate　is　soon　coated　with　a　film　of　iodine　of　a　fine　yellow　color；　it　is　then　removed　and　placed　over　the　accelerating　solution。　It　is　not　absolutely　necessary　to　perform　this　operation　in　the　dark；　although　a　bright　light　should　be　avoided。　Not　so　the　next　part　of　the　process；　viz；　giving　the　plate　its　extreme　sensitiveness；　or　coating　with　the　accelerating　liquids。　In　this　great　caution　should　be　used　to　prevent　the　slightest　ray　of　light　impringing　directly　on　the　plate；　and　in　examining　the　color　reflected　light　should　always　be　used。　A　convient　method　of　examining　the　plate；　is　to　make　a　small　hole　in　the　partition　of　the　closet　in　which　you　coat；　and　cover　it　with　a　piece　of　tissue　paper；　by　quickly　turning　the　plate　so　that　the　paper　is　reflected　upon　it　the　color　is　very　distinctly　shown。　Most　of　our　operators　are　not　so　particular　in　this　respect　as　they　should　be。

ACCELERATING　LIQUID。Of　these　there　are　several　kinds；　which　differ　both　in　composition　and　actionsome　acting　very　quickly；　others　giving　a　finer　tone　to　the　picture　although　they　are　not　so　expeditious　in　there　operations；　or　in　other　words；　not　so　sensitve　to　the　action　of　light。　　These　are　adopted　by　Daguerreotypists　according　to　their　tastes　and　predjudices。　They　are　all　applied　in　the　same　way　as　the　coating　of　iodine。　The　following　are　the　best。

Bromine　waterThis　solution　is　much　used　in　France；　and；　I　shall　therefore　give　its　preparation；　and　the　method　of　using　it；　in　the　words　of　M。　Figeau。　　〃Put　into　a　bottle　of　pure　water；　a　large　excess　of　bromine；　shake　the　mixture　well；　and　before　using　it；　let　all　the　bromine　be　taken　up。　　An　ascertained　quantity　of　this　saturated　water　is　then　diluted　in　a　given　quantity　of　distilled　water；　which　gives　a　solution　of　bromine　that　is　always　identical。〃　M。　Figeau　recommends　one　part　of　the　saturated　solution　to　thirty　parts　its　bulk　of　water；　but　M。　Lesebour　finds　it　more　manageable　if　diluted　with　forty　times。　　In　case　pure　distilled；　or　rain　water　cannot　be　procured；　a　few　drops　of　nitric　acidsay　six　to　the　quart　should　be　added　to　the　common　water。

Put　into　the　bromine　box　a　given　quantity　of　this　solution；　sufficient　to　well　cover　the　bottom；　the　plate；　having　been　iodized　to　a　deep　yellow；　is　placed　over