Gregory's Server@slyka @gigabecquerel The white is the unexposed part. It's potassium ferricyanide and ferric ammonium citrate. When it's exposed the normally yellow-green paper turns to Prussian blue - after washing out the paper the yellow-green tint goes away.
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Top-level
 @slyka @gigabecquerel The white is the unexposed part. It's potassium ferricyanide and ferric ammonium citrate. When it's exposed the normally yellow-green paper turns to Prussian blue - after washing out the paper the yellow-green tint goes away. 1 comment
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@philpem @gigabecquerel that's one way of making cyanotypes but there are other chemistries around, especially for commercially made cyanotype paper. And you can tell them apart by the color of the unexposed paper, hence my question.
EDIT: by unexposed here I mean the paper pre-exposure and development. Not the highlights of the image, those are obviously white.