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.
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.
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