The time of exposure and the strength of the developers are the most important factors in determining the quality and tone of the resulting transparency. Giving a short exposure and using a strong developer will ensure a vigorous picture with a rich velvety black tone. A long exposure, necessitating a weak developer, will produce fine gradation of light and shade, clear shadows and a warm brown tone.
When making transparencies for the window, cut a mask, with an opening, allowing for the border or margin on the ground glass it is intended to use. A suitable paper for this purpose is of deep orange color and moderately heavy; place the mask between the negative and the dry plate to be acted on, and it will protect the margin from the action of light, leaving it clear glass, and so exhibiting to better advantage the ornamented border of the ground or etched glass, which is placed against and covers and protects the film of the dry plate. When making lantern slides the mask is not necessary.
FERROUS OXALATE DEVELOPER FOR TRANSPARENCIES.
No. 1.
| Sulphate of iron (Anthony's) | 2 ounces. |
| Distilled or ice water | 32 ounces. |
| Sulphuric acid | 8 drops. |
No. 2.
| Neutral oxalate of potassium | 8 ounces. |
| Warm distilled water | 32 ounces. |
| Citric acid (or tartaric) | 60 grains. |
| Bromide of potassium | 180 grains. |
When about to use, mix equal parts of Nos. 1 and 2, always pouring No. 1 into No. 2. p216
The exposure having been made in the camera or in the printing frame, place the plate in the developing tray and pour upon it sufficient of the developing solution, mixed as directed, to cover the plate at once, and keep it in motion from time to time. Develop until detail in the high lights is plainly visible. When this is the case remove the plate, wash well and fix in hypo-solution.
| Water | 20 ounces. |
| Hyposulphite of soda | 6 ounces. |