american hand book of the daguerreotype-第7部分

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Potassa　Solution。The　use　of　a　solution　of　potassa　in　the　preparation　of　the　plate　was　suggested　in　the　early　history　of　the　Daguerreotype。　It　was　thought　to　possess　some　peculiar　property　for　improving　the　tone　of　the　impression。　　It　is　used　for　moistening　the　rotten　stone　in　polishing　the　plate；　and　may　be　prepared　by　putting　about　an　ounce　and　a　half　of　alcohol　in　a　close　bottle；　and　add　half　a　stick　of　caustic　potash。　This　will　soon　become　of　a　deep　red　color。　　For　use；　fill　your　small　bottle；　having　a　quill　in　the　cork；　with　alcohol；　and　add　a　few　drops　of　the　above；　or　enough　to　change　it　to　a　bright　orange　or　saffron　color。

A　Substitute　for　the　Hyposulphite　Solution。M。　DAGUERRE　recommends　the　use　of　a　solution　of　salt　water　for　removing　the　coating　off　the　plate。　I　found　this　of　some　service　at　one　time　during　my　travels。　My　hyposulphite　bottle　got　broke　and　its　contents　lost；　so　as　only　to　leave　enough　for　preparing　gilding。　　I　resorted　to　the　use　of　salt　solution；　and　found　it　to　answer　well。　　Make　a　saturated　solution　of　salt　in　water。　First　wash　the　plate　with　clear　water；　then　immerse　it　in　the　saline　solution；　when　it　should　be　agitated；　and　the　coating　will　soon　disappear。　Another　process　with　a　salt　solution　of　half　the　strength　of　the　above　is　very　interesting　and　effectual。　　The　plate　having　been　dipped　into　cold　water；　is　placed　in　a　solution　of　common　salt；　of　moderate　strength；　it　lies　without　being　acted　upon　at　all；　but　if　it　be　now　touched　on　one　corner　with　a　piece　of　zinc；　which　has　been　scraped　bright；　the　yellow　coat　of　iodine　moves　off　like　a　wave　and　disappears。　It　is　a　very　pretty　process。　　The　zinc　and　silver　forming　together　a　voltaic　pair；　with　the　salt　water　intervening；　oxidation　of　the　zinc　takes　place；　and　the　silver　surface　commences　to　evolve　hydrogen　gas；　while　this　is　in　a　nascent　condition　it　decomposes　the　film　of　iodide　of　silver；　giving　rise　to　the　production　of　hydriodic　acid；　which　is　very　soluble　in　water；　and　hence　instantly　removed。

This　process；　therefore；　differs　from　that　with　hyposulphite。　The　latter　acts　by　dissolving　the　iodide　of　silver；　the　former　by　decomposing　it。　　It　is　necessary　not　to　leave　the　zinc　in　contact　too　long；　or　it　deposits　stains；　and　in　large　plates　the　contact　should　be　made　at　the　four　corners　successively；　to　avoid　this　accident。

Gilding　Solution。To　one　pint　of　pure　rain　or　distilled　water　add　fifteen　grains　of　pure　chloride　of　gold；　and　to　another　pint　add　sixty　grains　of　hyposulphite　of　soda。　When　dissolved；　pour　the　gold　solution　into　the　hyposulphite　by　small　quantities；　shaking　well　after　each　addition。　The　soda　solution　must　not　be　poured　into　the　gold；　as　the　gold　would　be　immediately　decomposed；　and　the　solution　turn　black；　and　be　unfit　for　use。

Some　operators　add　muriate　of　potash　and　other　substances；　but　these　do　not　possess　any　advantage　except　in　cases　where　it　is　necessary　to　bleach　the　solarized　portions　of　the　impression；　and　when　such　is　the　case；　chloride　of　sodium　（common　salt）　is　probably　as　effective　and　is　the　most　convenient。　Add　about　a　teaspoonful　to　two　ounces　of　the　gilding。

Solution；　for　Increasing　the　Brilliancy　of　the　Daguerreotype。This　solution　will　have　the　effect　to　thoroughly　cleanse　the　surface　of　the　gilded　plate　and　excite　a　powerful　influence　on　the　general　character　of　the　impression。　To　a　solution　of　three　ounces　of　water；　in　which　is　dissolved　a　quarter　of　an　ounce　of　cyanide　of　potassium；　add　one　teaspoonful　of　a　solution　containing　six　ounces　of　water　and　half　an　ounce　of　each　pure　carbonate　of　potash；　alum；　common　salt；　gallic　acid；　sulphate　of　copper；　and　purified　borax。　While　the　plate　is　wet；　pour　on　a　little；　and　heat　it　with　a　powerful　blaze。　The　effect　will　be　quickly　produced；　in　from　three　to　fifteen　seconds。　Rinse　and　dry；　as　in　the　gilding。

Bleaching　Solution。Make　a　saturated　solution　of　muriate　of　ammonia　（sal　ammoniac）　in　pure　water；　and　filter　through　paper。　Reduce　with　an　equal　quantity　of　water　when　used。　　When　the　linen　or　any　other　portion　of　the　impression　is　badly　solarized；　after　removing　the　coating；　rinse　with　water；　then　pour　this　upon　the　surface　in　the　same　manner　as　the　gilding　solution。　If　the　solarization　be　very　deep；　apply　the　lamp　beneath；　and　warm　the　plate　a　trifle。　　Now　pour　off；　and；　without　rinsing；　apply　the　gilding。　　The　whole　operation　must　be　quickly　performed；　or　the　chlorine　soon　attacks　the　shades　of　the　picture。　When　properly　done；　however；　the　solarized　parts　are　restored　to　a　clear；　transparent　white。

Electro；　or　Cold　Gilding。This　process　I　have　adopted；　and　it　produces　exceedingly　beautiful　impressions　for　the　stereoscope；　adding　a　great　charm　to　the　pleasing　effect　of　that　instrument。　It　also　possesses　a　pretty　and　curious　effect　on　views。　It　is　easy　of　trial；　and　may　be　used　by　dissolving　one　gramme　of　chloride　of　gold　in　half　a　litre　of　ordinary　water；　and　thirty　grammes　of　hyposulphite　of　soda　in　another　half　litre　of　similar　water；　then　pour　the　solution　of　chloride　of　gold　into　that　of　soda；　by　little　and　little；　agitating　it　exactly　as　in　M。　Fizeau's　preparation；　of　which　there　is　but　a　variation。

When　you　wish　to　use　it；　pour　some　into　a　plate；　or　any　other　vessel　of　the　same　kind；　sufficient　to　cover　the　proof；　then；　after　having　added　to　it　a　drop　of　ammonia；　immerse　the　plate　in　it　as　soon　as　you　take　it　out　of　the　mercury…box；　after　having　wiped　its　back　and　edges；　and　agitate　the　mixture　quickly　from　right　to　left；　so　as　to　dissolve　rapidly　the　coating　of　iodide　of　silver　as　usual。　As　soon　as　the　plate　appears　white；　cease　all　rapid　motion；　but　continue　to　give　it　a　slight　undulating　one；　for　if　it　were　allowed　to　remain　still　for　only　a　few　minutes；　the　proof　would　be　clouded。　By　little　and　little；　the　surface　of　the　plate　takes　a　yellow　tint；　which　darkens　more　and　more；　approaching　to　bistre。　　You　stop　therefore；　at　the　color　you　wish；　and　when　the　proof　has　been　washed　and　dried；　in　the　manner　previously　explained；　it　will　be　found　to　be　fixed；　without　any　stain；　with　a　limpid　surface；　and　an　extraordinary　warm　tone。　If　you　were　to　augment　the　proportions　of　the　ammonia　or　chloride　of　gold；　the　operation　would　progress　much　quicker；　but　then　the　middle　of　the　proof　would　be　always　much　clearer　than　towards　the　border。　The　mixture　may　be　used　several　times　without　being　renewed。　It　does　not；　however；　give　such　a　beautiful　color　to　the　impression　as　when　it　is　newly　prepared。　　By　communicating　to　the　vessel　containing　the　solution　a　continual　motion；　the　impression；　when　once　immersed；　will　be　fixed。　　During　that　time；　and　while　attending　to　anything　else；　watch　its　color；　and　at　the　end　of　ten　minutes　or　a　quarter　of　an　hour；　take　it　out　of　the　bath　and　dry　it。

Agent　for　Neutralizing　Bromine；　Chlorine；　and　Iodine　Vapors。　Aqua　ammonia；　sprinkled　about　the　chemical　or　coating　room；　will　soon　neutralize　all　the　vapor　in　the　atmosphere　of　either　chlorine；　bromine；　or　iodine。　　No　operator　should　be　without；　at　least；　a　six…ounce　bottle　filled　with　ammonia。　A　little　of　its　vapor　about　the　camera…box　has　a　decided　and　happy　effect。　　Burnt　coffee；　pulverized；　has　also　the　property　of　destroying　the　vapors　of　the　above　chemicals；　as　also　almost　any　other　agent　employed　about　the　Daguerreotype　room。　Its　deodorizing　properties　are　such　that　if　brought　in　contact　with　air　filled　with　the　odor　of　decomposing　meat；　it　will　instantly　destroy　all　disagreeable　smell。　It　can　easily　be　used　in　the　Daguerreotype　room　by　placing　a　little　of　the　raw　bean；　finely　pulverized；　on　an　old　plate；　and　roasting　it　over　the　spirit…lamp。

Buff　Dryer。There　are　various　methods　for　keeping　buffs　dry　and　free　from　dust。　　Some　place　a　sheet　of　iron　against　the　wall　at　an　angle　sufficient　to　put　a　lamp　between　it　and　the　wall；　and　then　let　the　buff　rest　against　the　top　of　the　sheet。　　By　this　method　the　buff　is　for　its　full　length　close　to　the　heated　iron；　and　at　the　same　time　exposed　to　the　heated　atmosphere　and　any　dust　that　may　be　free。　I　would　recommend　some　arrangement　by　which　the　buff　would　be　inclosed。　I　have　found　the　following　to　answer　the　purpose　well；　which　is　a　box　of　sheet　iron　twenty　inches　long；　eight　wide　and　five　high；　with　one　end　left　open　and　the　other　closed；　the　cover　is　made　of　the　same　material；　with　the　edges　bent　over　to　go　on　and　off。　There　are　several　wires　running　through　the　centre　of　the　sides；　which　it　is　necessary　to　cover　with　cloth　or　paper　to　absorb　all　the　moisture　that　may　be　made　by　applying　the　heat；　and　the　buffs　are　put　in　and　taken　out　at　the　open　end。　In　order　that　the　heat　may　be　as　nearly　uniform　as　possible；　an　iron　bar　one　inch　wide；　eighteen　inches　long　and　one　half　inch　thick；　is　so　bent　that　the　centre　is　one　quarter　inch　from　the　bottom　of　the　box；　and　that　at　least　two　inches　of　each　end　come　in　contact　with　the　bottom；　this　being　riveted　on　the　bottom；　and　a　lamp　with　a　small　blaze　applied　to　the　centre　of　the　bar　of　iron。　This　will　constitute　one　of　the　best　and　cheapest　buff　dryers　in　use。　It　may　be　suspended　from　the　wall　by　placing　wires　around　it；　or　it　may　stand　upon　legs。　　Perhaps　a　more　convenient　plan　is　to　place　it　under　the　workbench　in　a　similar　position　to　a　drawer。　One　precaution　is　necessary：　　when　first　heating　the　dryer；　apply　but　a　very　gentle　heat。　　This　will　prevent　an　accumulation　of　moisture；　which　would　otherwise　pass　off　in　steam；　coming　in　contact　with　the　buff；　thus　causing　a　dampness。　　Another　caution：　never　have　the　temperature　of　the　air　in　the　heater　more　than　ten　degrees　above　that　which　surrounds　it。

When　wheels　are　used；　they　should　be　encased　in　a　sheet　iron　or　wood　case。　All　those　made　for　our　market　are　provided　in　this　respect。

Keeping　Buffs　in　Order。This　is　one　of　the　most　important　objects　to　arrest　the　attention　of　the　operator。　　Every　buff　is　more　or　less　liable　to　get　out　of　order　by　dust　falling　upon　or　coming　in　contact　with　the　polishing　powder　employed　in　cleaning　the　plate。　　The　edge　of　every　plate　should　be　thoroughly　wiped　and　freed　from　any　material　that　may　adhere　while　cleaning。　I　have　adopted　the　following　method；　which　proves　highly　successful：

Rub　the　buff　leather；　holding　the　face　down；　with　the　sharp　edge　of　a　pair　of　shears　or　a　piece　of　glass。　　Th