I. ALBUMENIZED-PAPER PRINTING PROCESSES.
There are two processes to be described under this head—a sun printing process and a development-printing process.
1..The Sun-printing Process.
To prepare the Albumen.—Take a sufficient number of fresh laid fowls' eggs, each of which contains nearly an ounce of albu men. Break each egg on the edge of a cup, and collect the white, or albumen, carefully rejecting the germ and yelk. Put all these whites together into a large basin, and add an equal quantity of clean rain water, and 6 grains of common salt to every fluid ounce of the mixture. Then beat the whole up to a -very stiff froth with a burich of quills. Allow it to settle till the next day, and decant the liquid, which is then fit for use.
The albumen, before being beaten up, is contained in small mem branous cells, which are broken in the process of beating, and the albumen liberated. This membranous tissue is highly soluble in an alkali, and the addition of a few drops of ammonia to the albumen has been recommended by M. Davanne, as a means of rendering it more fluid. The ammonia, being volatile, mostly escapes from the albumenized paper while drying.
The proportion of water to the albumen may be varied ac,cording to the nature of the subject to be printed. More water gives less glaze, and vice-versa.
To Albumenize the Paper.—Filter the salted albumen through two folds of fine muslin, previously damped, into a shallow bath, to the depth of at least a quarter of an inch. Turn back a corner of the paper, and place the face of it on the liquid, leaving it in contact for about a minute. Then hang it up to dry, by pinning the dry
corner to the edge of a shelf. Unless the membranous cells which contain the albumen are thoroughly broken up, it is very liable in drying to form streaks and waves on the paper.
The best paper to employ is that which has the smoothest and finest surface. The paper manufactured in France by Messrs. Marion, and Canson Freres, is generally preferred.
To excite th.e Paper.—Float the albumenized side on a 60 grain N. S. bath, for two minutes, and hang it up to dry in the dark.
This is the full strength of the bath. A weak negative requires a strong silver bath, and a short exposure ; a strong negative a weaker silver bath, and a longer exposure.
The Exposure to Light. —Expose in the pressure-frame either to sunshine or diffused light (the latter is best for feeble negatives abounding in half-tone), until the print is somewhat darker thail you wish it to be ultimately.
The particulars of this process will be found under the head of " Printing by Development." The paper must be albumenized in the same way as for sun-printing, and the remaining operations are identical with those for printing by devdopment on plain paper. It may be as well, however, in this process to omit the ammonia in the albumen bath, as free alkali in the paper is likely to oc,casion. discoloration in the process of development.