Cyanotype problem - blotching on paper

Hi everyone,

I had troubles with cyanotype lately as there are some blotches showing as you can see in the image. The blotching appears when the solution coated paper dries and then after exposure the blotches just remain there.
I am using liquid A+B cyanotype solution on paper Fabriano Accademia 200 gr. I would say 50% of the prints have this problem and I can't seem to understand why. I had this occur to me with better papers but rarely.

The size of the paper shown is A4, I am using brushes to coat the paper and there is no tap water included in the mixing of the cyanotype solution.

Also I am aware this paper is not ideal for cyanotype but I am curious as to why this mistake only occurs sometime.

Any advice or similar experiences?

Thank you!

Welcome to Photrio!

Try a different paper. This will likely fix your problem. Fabriano Accademia is an attractively priced paper that's great for sketching etc, but it may not be the best choice for cyanotype.
If you really want to continue using this paper, consider giving it a soak in a weak solution of citric, acetic or sulfamic acid and then hang up to dry. This should neutralize the carbonate buffer in the paper, which (together with subtle structural differences) is likely the cause for the bleaching you're seeing.

But really, using a better-suited paper is generally easier/more straightforward. The added benefit is that this gives you an excuse to head over to your nearest artist's store and sample all the nice papers they have!

koraks said:

…gives you an excuse to head over to your nearest artist's store and sample all the nice papers they have!

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I like trying new papers for both drawing and cyanotypes.. We have a new art supply store here and I went over to get a sheet of something new for an upcoming cyanotype project. “Nice papers” run up to $28/sheet. I ended up with a Bockingford hot press 140lb for about $5.

Hello - I am new to this site and quite new to cyanotype. I have a similar issue with some of my pieces where the sensitizer appears evenly covered on the paper but blotches appear during exposure. I am using the Classic formula and Canson Montval, a recommended paper, and also Daler Rowney Smooth Carriage paper. I am thinking I might not be letting the paper completely dry?

It would seem likely that alkaline buffer could cause that but I’m not positive. I use a sulfamic acid pre soak to remove those buffers. not much acid either maybe a tea spoon to a gallon seems to work fine. If a buffer is present it will bubble a bit in the bath. You’re already getting lovely blues with your technique but for me an acid pre wash seems to get me deeper blues. It will also reduce your exposure time significantly. In the states you can get the acid at hardware stores for cheap.

It would seem likely that alkaline buffer could cause that but I’m not positive.
Thanks for the reply to my inquiry. Per various sources, Canson Montval, is listed as "acid free" but maybe that isn't answering about a buffer? I am willing to give the pre-soak a try to see the difference. I have Sulfamic Acid to use.

msh said:

Per various sources, Canson Montval, is listed as "acid free"

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That's a good indicator that it's indeed buffered, as virtually all papers are. Just try a different paper; quite a few papers work well with Cyanotype without further treatment. Especially classic Cyanotype is very forgiving.