Ferric ammonium citrate green or brown for cyanotype?

Green and brown ferric ammonium citrate are not simply the same substance with a different color. They generally differ in iron content and behavior. For classic cyanotype recipes, the green variant is usually used, because many well-known formulations are tailored to it. Therefore, do not replace green and brown gram for gram without a test or adjusted formula.

What does ferric ammonium citrate do?

Ferric ammonium citrate is the light-sensitive iron component of solution A. When the coated layer receives UV light, some of the iron changes. During rinsing and the reaction with potassium ferricyanide, insoluble Prussian blue is formed in paper or textile fibers.

Green ferric ammonium citrate

The green quality usually has a lower iron content than the brown variety and is widely used for photography and cyanotype. The exact composition may differ per supplier. Therefore, always check specification, purity and recommended concentration on the product label.

• Many classic cyanotype instructions are written for green.
• The solution is light sensitive and should be stored in a dark place.
• Old or contaminated solution can affect contrast and coating.

Brown ferric ammonium citrate

The brown quality usually contains more iron and can dissolve and react differently. That does not automatically make it better or worse, but it does make it a different raw material. A recipe developed for green may become too concentrated or less predictable with brown. Use a validated formula for the chosen quality.

Why replacing gram for gram is not wise

When the iron content differs, the same mass does not provide the same amount of active iron. pH, water content and product specification also play a role. Therefore, treat the color name as an indication, not as a complete technical specification. Note supplier and batch when reproducibility is important.

Which variant do you choose for cyanotype?

Follow the recipe that comes with your kit or raw material. For a classic beginner setup, green ferric ammonium citrate for cyanotype is usually the most logical choice, combined with potassium ferricyanide . Use the supplier's instructions above any recipe on the Internet.

Problems that are not just due to the color variant

• Pale print: can also be caused by underexposure, alkaline paper or insufficiently dry coating.
• Stains: often a result of paper, too much solution or contaminated tools.
• Precipitation: may be related to water quality, concentration, temperature or contamination.
• Little detail: check negative contact and exposure before replacing the chemistry.

Use full diagnostics in Cyanotype failed? .

Storage

Store powder dry, well closed and according to the safety data sheet. Store the stock solution dark and cool in a clearly labeled bottle. Use clean pipettes and never pour back mixed working solution. Date each bottle and first make a test strip for older solutions.

Work safely

Avoid inhalation of powder, ingestion and contact with eyes or skin. Wear gloves when mixing and coating, do not work with food and read the safety data sheet. See cyanotype chemical explanation for more context.

Frequently asked questions

Is darker powder always brown quality?

No. Color may change due to batch, moisture, age and light. Use product name and specification, not just appearance.

Can I combine both variants?

This makes the actual concentration difficult to control. It is better to use one known quality and a suitable recipe.

Why does my kit name a different concentration?

Cyanotype has several formulations. Follow the complete instructions of one system and do not combine separate percentages from different recipes. The cyanotype ratio guide explains how to read percentages.