For reproduction of simple line drawings iodized collodion is used which consists of 2 per cent. raw collodion composed of—
| Ether | 1,000 | ccm. |
| Absolute alcohol | 1,000 | ccm. |
| Pyroxylin | 40 | g. |
Iodizing is done with
| Sodium iodide | 15 | g. |
| Cadmium iodide | 15 | g. |
| Cadmium bromide | 8 | g. |
| Potassium iodide | 1 | g. |
The last salt is dissolved in a few drops of distilled water, the other salts are dissolved in one part of the absolute alcohol. The iodizing solution is filtered into the raw collodion, which has already been allowed to settle and filtered, and allowed to stand for some days.
The sensitizing solution is nitrate of silver in the proportion of 1 : 10, with larger sizes 1 to 12–1 to 14, and the silver bath is faintly acidulated with chemically pure nitric acid.
For a monochrome subject the exposure lasts according to the size of the reproduction, and the rapidity of the objective, from three to ten minutes.
For development an iron developer is used, consisting of:—
| Water | 4000 | ccm. |
| Ferrous sulphate | 150 | g. |
| Copper sulphate | 75 | g. |
| Alcohol (40 per cent.) | 250 | ccm. |
| Glacial acetic acid | 125 | ccm. |
The iron developer, with addition of sulphate of copper, is to be preferred for short exposures to iron and lead developer. If the plate has been correctly exposed the image gradually appears after a short time, and very soon gets vigorous. When the details appear in the deepest shadows the development must be immediately stopped, otherwise fogging will ensue. If the image does not gain vigour by long development it was under-exposed; with over-exposure the image appears quickly and remains thin. The developer, when fresh, works fairly quickly; older developers work slower, but give very clear negatives.