the history and practice of the art of photography-第13章

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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　it；　the　time　the　plate　should　be　exposed　must　be　ascertained　by　making　a　few　trials；　it　averages　from　twelve　to　forty　seconds。　When　once　ascertained；　it　is　the　same　for　any　number　of　plates；　as　the　solution；　which　of　course　would　become　weaker　and　weaker；　is　changed　after　every　operation；　the　same　quantity　being　always　put　into　the　pot。

Chloride　of　Iodine。This　is　prepared　by　introducing　chlorine　gass　into　a　glass　vessel　containing　iodine；　the　iodine　is　liquified；　and　the　above　named　compound　is　the　result。　Operators　need　not；　however；　be　at　the　trouble　and　expense　of　preparing　it；　as　it　can　be　obtained　prefectly　pure　of　Mr。　Anthony；　205　Broadway；　N。　Y。；　as　also　all　of　the　chemicals　herein　enumerated。　The　compound　is　diluted　with　distilled　water；　and　the　plate　submitted　to　its　action　till　it　is　of　a　rose　color。　　Chloride　of　iodine　alone；　is　seldom　if　ever　used　now　by　American　operators；　as　it　does　not　sufficiently　come　up　to　their　locomotive　principle　of　progression。　The　next　is　also　eschewed　by　the　majority；　although　many　of　our　best　artists　use　no　other；　on　account　of　the　very　fine　tone　it　gives　to　pictures。

Bromide　of　Iodine。This　is　a　compound　of　bromine　and　chloride　of　iodine。　　In　mixing　it；　much　depends　upon　the　strength　of　the　ingredients；　an　equal　portion　of　each　being　generally　used。　Perhaps　the　best　method　of　preparing　it；　is　to　make　a　solution　in　alcohol　of　half　an　ounce　of　chloride　of　iodine；　and　add　the　bromine　drop　by　drop；　until　the　mixture　becomes　of　a　dark　red　color；　then　dilute　with　distilled　water；　till　it　assumes　a　bright　yellow。　Put　about　half　an　ounce　of　this　compound　into　the　pot；　and　coat　over　it　to　a　violet　color；　change　the　solution　when　it　becomes　too　weak　to　produce　the　desired　effect。

Another。Mix　half　an　ounce　of　bromine　with　one　ounce　of　chloride　of　iodine；　add　two　quarts　pure　distilled　water；　shake　it　well　and　let　it　stand　for　twelve　hours　then　add　twenty…five　drops　of　muriatic　acid；　and　let　it　stand　another　twelve　hours；　occasionally　shaking　it　up　well。　Dilute　six　parts　of　this　solution　in　sixteen　of　water。　　Coat　over　dry　iodine　to　a　deep　yellow；　then　over　the　sensitive　to　a　deep　rose　color　approaching　purplethen　back；　over　dry　iodine　from　four　to　eight　seconds。

Roach's　Tripple　Compound。This　is　one　of　the　very　best　sensitive　solutions；　and　is　very　popular　among　Daguerreotypists。　To　use　this；　take　one　part　in　weight；　say　one　drachm；　of　the　compound　and　dilute　it　with　twelve　of　water；　coat　over　dry　iodine　to　yellow；　then　over　the　compound　to　a　rosy　red。　The　effect　in　the　camera　is　quick；　and　produces　a　picture　of　a　fine　white　tone。

Gurney's　Sensitive。This　is　another　preparation　of　bromine；　and　gives　a　fine　tone。　　To　two　parts　of　water　add　one　of　the　sensitive；　and　put　just　sufficient　in　the　box　to　cover　the　bottom；　or　enable　you　to　coat　in　from　eight　to　ten　seconds。　Coat　over　dry　iodine　to　a　dark　yellow；　and　over　the　quick　till　you　see　a　good　change；　then　back　over　the　dry　iodine　from　two　to　three　seconds。

Bromide　of　Lime；　or　Dry　Sensitive。This　is　a　compound　but　recently　introduced；　and　is　becoming　somewhat　of　it　favorite；　owing　principally　to　the　slight　trouble　it　gives　in　its　preparation；　and　the　tone　it　imparts　to　the　picture。　　To　prepare　it；　fill　your　jar　about　half　or　quarter　full　of　dry　slacked　lime；　then　drop　into　it　bromine；　till　it　becomes　a　bright　orange　red。　The　plate　is　generally　coated　over　this　compound；　after　the　iodine　coating　to　yellow；　to　a　violet；　or　plum　color；　but　it　will　work　well　under　any　circumstances；　the　color　being　of　little　consequence；　if　coated　from　thirty　to　ninety　seconds；　according　to　its　strength。

Mead's　Accelerator。I　merely　mention　this　as　being　in　the　market；　not　knowing　any　thing　in　regard　to　its　merits。　The　directions　given　for　its　use　are　as　follows：　Mix　one…third　of　a　bottle　with　a　wine　glass　full　of　water；　coat　the　plate　over　dry　iodine　to　a　dark　gold　color；　then　over　the　accelerator　to　a　violet；　then　back　over　dry　iodine；　or　chloride　of　iodine；　from　three　to　five　seconds。

Chloride　of　Bromine。M。　Bissou；　a　French　experimentalist；　has　found　that　bromine　associated　with　chlorine；　prepared　in　a　similar　manner　to　chloride　of　iodine；　already　described；　a　solution　of　bromine　being　substituted　for　the　iodine；　is　a　very　sensitive　solution；　by　means　of　it　daguerreotype　proofs　are　obtained　in　half　a　second；　and；　thus　very　fugitive　subjects　are　represented；　making　it　the　very　best　compound　for　taking　children。　So　quick　is　its　operation；　that　even　persons　or　animals　may　be　taken　in　the　act　of　walking。

Hungarian　Liquid。This；　I　believe；　has　never　been　used　here；　or　imported　into　this　country；　and　the　composition　of　it　is　not　generally　known；　even　in　Europe；　where　it　has　taken　precedence　of　all　others。　It　acts　quickly　and　with　considerable　certainty。　　It　is　used　by　diluting　it　with　from　ten　to　fifteen　times　its　bulk　of　water；　putting　a　sufficient　quantity　into　the　jar　to　cover　the　bottom。　The　plate　being　previously　iodized　to　a　light　yellow；　is　submitted　to　this　mixture　till　it　assumes　a　light　rose　tint。

Bromine　and　Fluoric　Acid；　in　combination；　are　used　by　some　Daguerrean　artists　as　a　sensitive；　but　any　of　the　above　compounds　are　better；　besides　this；　the　fluoric　acid　is　a　dangerous　poison；　and　the　quick　made　from　it　will　not　repay　the　risk　to　the　health　in　using　it。

As　I　have　before　said；　great　caution　should　be　observed　in　examining　the　color　of　the　plate；　even　by　the　feeble　light　allowed；　which；　when　attained；　must　be　immediately　placed　in　the　holder　belonging　to　the　camera　and　covered　with　the　dark　slide。　You　then　pass　to　the

THIRD　OPERATION。Submitting　the　Plate　to　the　action　of　Light　in　the　Camera。Experience　alone　must　guide　the　operator　as　to　the　time　the　plate　should　be　exposed　to　the　influence　of　the　light；　this　being　dependent　on　a　variety　of　circumstances；　as　clearness　of　the　atmosphere　and　here；　a　reference　to　the　hygrometer　will　be　of　advantage　time　of　day；　object　to　be　taken；　and　the　degree　of　sensitiveness　imparted　to　the　plate　by　the　quickstuff。　　As　I　have　before　said；　the　artist　should　be　careful　to　see　that　the　interior　of　the　camera　is　clean　and　free　from　dust；　as　the　small　particles　flying　about；　or　set　in　motion　by　the　sliding　of　the　holder　into　the　box；　attach　themselves　to　the　plate；　and　cause　the　little　black　spots；　by　which　an　otherwise　good　picture　is　frequently　spoiled。　Care　should　also　be　taken　in　withdrawing　the　dark　slide；　in　front　of　the　plate；　from　the　holder；　as　the　same　effect　may　be　produced　by　a　too　hasty　movement。　　The　lens　is　the　last　thing　to　be　uncovered；　by　withdrawing　the　cap　c。　fig。　5。；　which　should　not　be　done　until　you　have　placed　the　sitter　in　the　most　desirable　position。　When；　according　to　the　judgment　and　experience　of　the　operator；　the　plate　has　remained　long　enough　to　receive　a　good　inpression；　the　cap　is　replaced　over　the　lens；　and　the　dark　slide　over　the　plate；　which　is　then　removed　from　the　camera。

Daguerreotypists　generally　mark　time　by　their　watches；　arriving　at　the　nearest　possible　period　for　producing　a　good　picture　by　making　several　trials。　As　a　ready　method　of　marking　short　intervals　of　time　is；　however；　a　very　important　consideration；　and　as　any　instrument　which　will　enable　an　artist　to　arrive　at　the　exact　period；　must　be　an　improvement；　and　worthy　of　universal　adoption；　I　will　here　describe　one　invented　by　Mr。　Constable　of　England；　which　he　calls　a

Sand　Clock；　or　Time　Keeper。〃It　consists　of　a　glass　tube；　about　twelve　inches　long；　by　one　in　diameter；　half　filled　with　fine　sand；　similar　to　that　used　for　the　ordinary　minute　glasses；　and；　like　them；　it　has　a　diaphram；　with　a　small　hole　in　the　centre　through　which　the　sand　runs。　The　tube　is　attached　to　a　board　which　revolves　on　a　centre　pin；　on　the　side　is　a　graduated　scale；　divided　into　half　seconds；　the　tube　is　also　provided　with　a　moveable　index。　This　instrument　is　attached；　in　a　conspicuous　place；　to　the　wall。　The　glass　tube　being　revolved　on　its　centre；　the　index　is　set　to　the　number　of　half　seconds　required；　and　the　sand　running　down；　the　required　time　is　marked　without