Cyanotype proportions: recipe in grams and milliliters
A classic cyanotype recipe consists of two stock solutions that are mixed in equal volumes only just before use. By keeping solutions A and B separate, they remain usable longer and you prevent the light-sensitive working solution from reacting in the bottle. Weigh accurately, label everything and always follow the instructions of your specific kit or supplier if they differ.
The classic relationship
A commonly used classic formulation is:
- Solution A: 20% ferric ammonium citrate in water.
- Solution B: 9% potassium ferricyanide in water.
- Working solution: Mix A and B at a ratio of 1:1 by volume just before use.
Twenty percent here means 20 grams of substance supplemented with water to a total volume of 100 milliliters. Nine percent means 9 grams made up to 100 milliliters. There are also recipes with other concentrations; therefore do not randomly mix parts from different systems.
Quantities for different volumes
| Eindvolume voorraadoplossing | Oplossing A bij 20% | Oplossing B bij 9% |
|---|---|---|
| 25 ml | 5 g ferric ammoniumcitraat | 2,25 g kaliumferricyanide |
| 50 ml | 10 g ferric ammoniumcitraat | 4,5 g kaliumferricyanide |
| 100 ml | 20 g ferric ammoniumcitraat | 9 g kaliumferricyanide |
First fill with about three quarters of the required water, dissolve the substance completely and then fill to the final volume. “20 grams plus 100 ml of water” is not the same as “20 grams added to 100 ml”.
Supplies
- A scale that measures small quantities reliably.
- Two separate, clean measuring cups and stirrers.
- Distilled or demineralized water when tap water causes problems.
- Two light-tight or amber-colored, clearly labeled bottles.
- Gloves and a protected work surface.
The loose raw materials are available as green ferric ammonium citrate and potassium ferricyanide . If you don't want to weigh the first time, use a complete starter kit .
Mix step by step
- Clean work surface and materials and put on gloves.
- Label bottle A and bottle B before you begin.
- Weigh the correct amount for solution A and dissolve it in some of the water.
- Make up to the chosen final volume and close bottle A.
- Use clean tools and repeat separately for solution B.
- Store both bottles in a cool, dark place and out of the reach of children.
- Just before coating, mix only a small amount of A and B in a 1:1 ratio.
How much working solution do you need?
That depends on size, paper and coating method. Start sparingly: a few milliliters of mixed solution are often enough for several small sheets. A slightly absorbent paper requires less than rough or highly absorbent material. Make a note of what you actually consume; after that you can mix virtually without residue per session.
Why solutions A and B remain separate
The combination is light sensitive and responds faster than the separate stock solutions. Therefore, do not store the mixed working solution for later and never pour residues back into bottle A or B. Use separate pipettes or rinse them thoroughly to avoid cross-contamination.
Common calculation errors
- Confusing grams and milliliters: a solid is weighed; water or solution is measured by volume.
- Do not add water to final volume: this will make the solution too dilute.
- Using a kitchen spoon: powders have different densities; spoons are not accurate.
- Pre-mix all working solution: this causes the mixture to age unnecessarily quickly.
- Combine recipes: use concentrations as one coherent system.
Safety and storage
Do not use eating utensils, avoid dust formation and prevent inhalation, ingestion and prolonged skin contact. Do not mix potassium ferricyanide with strong acids or heat it. Consult the safety data sheets of the purchased substances and follow local regulations for residues and waste water. Also read Is cyanotype poisonous? for a sober explanation of the risks.
Frequently asked questions
Can I use tap water?
Often yes. In case of precipitation, unexpected color or variable results, distilled or demineralized water is a simple control test.
Why are there crystals in the bottle?
This can be caused by evaporation, low temperature or too high a concentration. Let the bottle come to room temperature and check if everything dissolves again. Do not use a contaminated or highly modified solution blindly for important work.
How long do the solutions last?
That depends on water quality, storage, contamination and recipe. Store in a dark and cool place, date the bottles and test older solution on a small strip before coating a full print.