Quote Originally Posted by Akki14 View Post
This is more or less pure cotton canvas as in the material not the artist's medium. We bought it on a huge roll for re-covering theatre flats (large background type canvas & wood things) and I got the offcuts for free. It's not been sized or gessoed or anything of the sort. Just hadn't been washed as I was in a bit of a rush in the circumstances.
I see. But the fact that you're experiencing fogging right after coating implies that there's something wrong with the material - Cyanotype, especially New Cyanotype is a very good purity tester; you'll get inferior results with non-pure / non-suitable materials. Pure cotton never fogs - at least in my experience (I tried at least 4 different cotton fabrics from different sources and never experienced fogging). Does the same sensitizer work well with other substrates? Are you using the same tool for coating and/or the same coating method? Are you using the same water? BTW, don't overlook my suggestion of using silk -> it's a beautiful and most noble fabric for your fine-art prints + it needs neutral/acidic environment - just like Cyanotype.

Another note: I don't include dichromate in my classic sensitizer; I use dichromate just in the new formula. Maybe dichromate tans and stains the fabric?

Hope this helps,