In taking Collodion Pictures, it is always advisable for the sitter to be arranged before the glass is taken from the bath: this will save time and there will be less liability of the collodion drying.
A Good Negative may be known by its possessing the following characteristics:—By transmitted light the figure is bright, and appears to stand out from the glass; the dark shadows are clear, without any misty deposit of metallic silver; the high lights black almost to complete opacity.
A Glass Coated with Collodion, if kept too long before immersion in the bath, will not be equally sensitive over its surface; the parts most dry being the least sensitive.
Glass Pans, for Scales, can be procured by every one at trifling expense: Take a watch crystal, and place in the common metal pan; balance this with lead, or any weight: this can easily be kept clean, and is the most advisable for weighing all deliquescent salts, and chemicals employed in the collodion process.
Caution.—Persons engaged in making collodion, and using ether and alcohol, must bear in mind that these chemicals are very inflammable; hence extreme caution is necessary to avoid exposing them to the flame of a lamp or candle. I have known of several serious accidents, of recent date, all of which were caused by the imprudence of the experimenter in the particular above mentioned.
Wipe the Plate-holder every time before the glass is put into it: this will prevent spots, which might otherwise occur from the presence of nitrate of silver solution which drained from the plate previously used. These spots are of an opaque yellowish tinge, and in shape resemble the stain which would be occasioned by a splash of water.
Glass jar Positives.—A good white or light-green glass will answer for the collodion coating. Glass which contains air-spots can be used, if it be placed in such a manner as to let the light of the image come over them, as the spots cannot be seen through the opaque surface. Only the best white glass should be used for covering the picture. Some operators use the convex glass, which is very clear, and answers the purpose.
The Nitrate of Silver Bath should be kept covered, except when in use.