Introduction
Ralston introduced a notation for basic recipies for dichromated gelatin emulsions. He use a sequence of three numbers that indicated the quantities of dichromate, gelatin, and water, respectively, used in the formulation. For example, 5-30-200 in Ralson's scheme meant 5 grams of dichromate with 30 grams of gelatin and 200 grams (exactly equivalent to ml) of water made up the recipe. The normal for Ralston's notation was 30 grams of gelatin, while the dichromate and water ratios were allowed to vary.
Many amateur holographers use common food-grade gelatin in their work. Knox Gelatin is the most typical. In the United States, Know Gelatin is available in convenient 1 oz. packets. An ounce is roughly 14 grams, so it can be convenient to express Ralston recipes using a 14 gram reference for gelatin instead of the more common 30 grams. Common Ralston recipes then become:
| Ralston Recipe | Rescaled Recipe |
| 5-30-250 | 2.3-14.250 |
| 10-30-600 | 4.4-140200 |