Collodion Ratio Calculator
Enter a multi-part ratio from your own reference source and a target batch size to see each part scaled proportionally.
Scaled batch
Scaling, not sourcing, a historical ratio
Given a documented ratio of parts — say 3:2:1 — the total number of "shares" is the sum of the parts, six in that example. Each part's volume in a target batch is simply its share of that total: part ÷ total shares × target batch size. Scale the batch up or down and every part grows or shrinks together, keeping the same proportions the original recipe called for.
This calculator is a general ratio scaler applied to the multi-part recipes common in historical photographic literature. It performs the arithmetic only and carries no chemical, safety, or sourcing information of its own.
Frequently Asked Questions
Why are historical recipes written as ratios instead of exact amounts?
Wet-plate and other 19th-century processes were documented long before standardized modern measurement was universal in the darkroom, and practitioners routinely scaled a known-good recipe up or down for whatever batch size they needed that day. A ratio travels well across unit systems and batch sizes in a way a single fixed recipe doesn't.
Does this tool tell me what the collodion recipe should be?
No. You supply the ratio parts from your own archival source, historical text, or reference material; this calculator only scales those numbers proportionally to your target batch size. It has no built-in formulation and does not recommend specific chemicals, proportions, or sourcing.
How many parts can I scale at once?
The tool here supports up to three named parts, which covers most documented ratios, but the underlying math (scaling any list of ratio numbers so they sum to a target total) works for any number of parts.
Is wet-plate collodion chemistry something I should try without guidance?
Historical wet-plate collodion work involves flammable solvents and other hazardous materials, and should only be attempted with proper training, protective equipment, ventilation, and current safety data sheets for every material involved. This site covers the history and math of the process, not a how-to for handling the chemistry.
Educational and historical-reference tool only — plain ratio arithmetic on numbers you supply. Not a chemical formulation, sourcing guide, or safety guidance. Historical photographic chemistry can involve flammable and toxic materials; consult current safety data sheets and a qualified instructor before any hands-on process work.