American Hand Book of the Daguerreotype — Story, Setting & Ideas

The Chemistry of Accelerators

The excerpts focus heavily on preparing "accelerators"—compounds that speed up the plate's sensitivity. Humphrey details making hydrate of lime by slaking quicklime in warm water, warning against overheating lest it revert to carbonate. He specifies using "oyster-shell lime" for purity, as impurities prevent bromine combination. For bromide of lime, he instructs filling a four-quart bottle two-thirds full of hydrate, adding bromine in increments, shaking well, and letting it stand for hours. The compound "improves by age." The desired color is a "fine red." These instructions reveal a trial-and-error craft: the practitioner must judge colors and textures, not just follow fixed ratios.

Gurney's Two-Temperature System

Humphrey presents Gurney's American Compound in two formulations: No. 1 for temperatures above 65–70°F, No. 2 for lower. No. 1 adds pulverized burnt alum, a trace of chloride of lime, and dry iodine to the hydrate of lime—just enough iodine to prevent "flaring" or "scum-coating." The iodine must be "thoroughly combined" over one or two days before adding bromine to a "light red color." No. 2 omits iodine. The coating sequences differ: for No. 1, coat iodine to "bright yellow," then compound to red, then recoat iodine for one-sixth the first time; for No. 2, recoat for one-fourth to one-half. These precise variations show how environmental conditions dictated recipe adjustments.

Dry Quick and Starch Additives

Another compound, Dry Quick, No. 1, mixes equal quarts of hydrate of lime and finely pulverized starch, then adds bromine until "deep yellow or pink." Humphrey notes the claim that starch holds bromine longer, but he doubts it: "Our experience in practice has led us to the conclusion that there is no great difference as respects durability." However, he concedes a difference in "the tone of the impressions." He adds that starch may be added to any dry mixture. The coating instruction is similar: iodine to deep yellow, then quick to red, recoat one-sixth. This section exemplifies the book's empirical tone—Humphrey tests claims against his own practice and reports honestly.

Reading the Recipes as a Practitioner

These excerpts are not a narrative but a set of operational protocols. The reader must interpret phrases like "coat over the iodine to a rose red" as visual benchmarks, not numerical targets. The repeated warnings—against overheating lime, against impurities, against insufficient iodine—indicate common failure points. The book assumes the reader has equipment (camera, buffs, mercury bath) and chemicals (iodine, bromine, hyposulphite). The dedication to Gurney and the mention of "Gurney's American Compound" suggest a community of practitioners sharing refinements. A first-time reader should approach the text as a lab manual: read each recipe fully before mixing, and note the color descriptions as critical quality checks.

Humphrey's handbook rewards careful, sequential reading. The recipes build on each other: understanding hydrate of lime is prerequisite to bromide of lime, which is prerequisite to Gurney's compounds. The book's value lies in its specificity—exact bottle sizes, color targets, and warnings against common errors. Readers interested in historical photographic practice will find a detailed record of mid-19th-century chemical craft, while modern practitioners may adapt the methods with appropriate safety precautions.