>> I use a diluted hydrochloric acid bath to heighten the blues in my
>> cyanotypes.
Since no one commented on this sentence, I would like to add a note:
The *hydrochloric acid* bath will heighten the blues if your water is
alkaline, like ours. We have found that the blue gets quite faded after
a half hour wash in our tap water. No wonder - I think the ph meter
read 3.5! (Don't remember exactly, except it was VERY alkaline) From
then on we always add a few drops of Stop Bath in the wash, and have no
problems since.
Sam