AlternativePhotography.com: Does cyanotype chemicals react to metal?

Cyanotype chemicals in a rusty old jar

The myth: Don’t use a brush with a metal ferrule! True or not? Malin Fabbri finds out.

It has been said that a brush with a metal ferrule cannot be used for coating cyanotypes, because the metal on the brush may react with the cyanotype chemicals. True or false?

Taking this myth to the extreme, 4 sets of solutions were prepared.

Using glass bowls for mixing the chemicals and a hake brush.

Using glass bowls and a brush with a metal ferrule.

Mixing the chemcials in a rusty jar.

Mixing the chemcials in a rusty jar and leaving the mixed solution in the rust for 24 hours before coating the paper.

Coating the papers, the solution C from the rusty jar was slightly greener than A and B from the glass bowls. Solution D that had been left in the rusty jar for 24 hours was dark green, almost blue when coated onto paper. Clearly a reaction had taken place.

AA. Using glass bowls for mixing the chemicals and a hake brush.

B.Using glass bowls and a brush with a metal ferrule.

C. Mixing the chemcials in a rusty jar.

D. Mixing the chemcials in a rusty jar and leaving the mixed solution in the rust for 24 hours before coating the paper.

A negative and a Stouffer step wedge were used to make four prints. The prints using solution A (top image) and B from the glass bowl and solution C from the rusty jar were almost identical. But, the print using solution D that had been sitting in the rusty jar for 24 hours was quite different (bottom image). The highlights had oxidized and turned blue.

True or false? The conclusion: False! Though a rusty jar is not recommended when mixing chemicals - a brush with a metal ferrule can be used with no harm. If there is a reaction, it is too small to be noticable.

A lot more about cyanotypes can be learnt in the book Blueprint to cyanotypes.

Blueprint to cyanotypes - Exploring a historical alternative photographic process
by Malin Fabbri and Gary Fabbri
A well illustrated step-by-step guide to cyanotypes.

A lot more information on the process, chemicals, coating, exposure, printing, making negatives, washing and troubleshooting is available in this book.

Strongly recommended for beginners

Looking for chemicals or kits? is one of our recommended suppliers and ships worldwide.
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Cyanotype chemicals in a rusty old jar

The myth: Don’t use a brush with a metal ferrule! True or not? Malin Fabbri finds out.