SearchAbout This SiteTreatment ForumVideo clipsGalleryScienceLibraryTechnology

THE PHOTOGRAPHIC NEWS. March 4, 1859. p.303

A Catechism of Photography

ALBUMEN PROCESS.

Q. Has the albumen process been long known to photographers?

A. It has, having been used many years before the introduction of the collodion.

Q. By whom was the process invented?

A. Sir John Herschel in England, and M. Nièpce de St. Victor in France, who exhibited the first negatives obtained on glass by means of albumen.

Q. Is it a difficult process?

No, the plan is simple enough, but requires considerable care in manipulation.

Q. Is it a successful process?

A. Yes; it rivals the daguerreotype in sharpness of definition.

Q. Is it more or less sensitive than the collodion?

A. It is less sensitive than the collodion, requiring an exposure of minutes where the collodion demands seconds. It surpasses collodion, however, in its capability of rendering depth and transparency of shadow, with extreme brilliancy in the high lights.

Q. What is albumen?

A. White of egg. Albumen is the true starting point from which all tissues are formed, as the egg contains no other nitrogenous compound except albumen; the yolk containing, besides albumen, a yellow fat only.

Q. What is the chief characteristic of albumen?

A. Its coagulability by heat.

Q. How is soluble albumen obtained?

A. It may be obtained in a soluble form by evaporating it at a temperature below 120°. It is then a dry, horny, brittle mass of a yellowish colour, tasteless, and without odour. It is insoluble in alcohol and ether, but soluble in water containing alkaline salt or chloride of sodium. It is an fact that albumen cannot exist in the soluble state in the absence of mineral constituents, and that a slight alkaline reaction is the best condition for photographic operation.

Q. What albumen is best adapted for photographic purposes?

A. That of the hen's egg. The eggs should be perfectly fresh, and not more than four or five days old.

Q. How is the albumen to be obtained from them?

A. By breaking each egg separately into a shallow dish, and retaining the yolk and germ in the shell.

CLEANING THE GLASS.

Q. What sort of glass is the best adapted for this purpose? A. New patent plate glass.

Q. How should the glass be cleaned?

A. By fixing it firmly in a wooden screw or vice, perfectly flat, and rubbing it with a pellet of cotton wool dipped in a solution of alcohol, ammonia, water, and tripoli.

Q. In what proportion should these ingredients be mixed?

A. As follows:--

Alcohol 1 ounce.
Strong liquid ammonia ¼"
Water 1½ "
Tripoli 1 "

Q. How do you proceed with the cleaning process ?

A. As soon as the plates have been thoroughly rubbed over with the solution, they should be allowed partially to dry, then rubbed off with a clean piece of wool, and, finally, polished with another pellet of the same material. The back and edges should be dusted with a hog's hair brush, and the plates then put away in a dry clean box.

ALBUMENISING THE GLASS.

Q. How should the albumen be prepared?

A. In the following manner:--

Albumen 12 ounces.
Saturated solution iodide of potassium ¼ "
Bromide of potassium 23 grains
Water 15 "
Solution of caustic potash 1 drop

These ingredients, having been put together in a. large bottle, should be thoroughly shaken until the bottle is quite filled with white foam. The solution should then be allowed to stand for five or six hours in a cool place; One hour before the solution is to be used, it should be decanted into a glass measure. .

Q. How is it to be spread over the glass?

A. The glass should be taken on the tips of the fingers of the hand, and the albumen poured on to the surface in a sufficient quantity to cover the plate; the excess must be poured off into the measure. It is best to prepare a number of plates at once; four dozen can easily be coated in an hour; each plate takes a considerable time to dry; and, thus albumenised, will keep for any length of time.

(To be continued.)


Home ~ Library ~ Science ~ Technology ~ Gallery ~ Video ~ Forum ~ About ~ Search