Quote Originally Posted by eggshell
EricNeilson, Oh yes, I'm using a hairdryer to dry the coating. Didn't occur to me that the paper is de-humidified in this manner. Thanks for making me realise that.
Then the question becomes, How much time elapses between coating /drying and then printing? If you are drying your paper with a hair dryer, and then printing straight away, I'd guess that your paper,in an environment of 72% RH is getting down to somewhere between 20% and 35% RH. It would need to rest for about 20 minutes to 30 minutes, before it would get back to 72% as in the room. That all of course depends on how long you dry, what you dry it on, ...

The RH in the paper at time of exposure will also be influenced by the paper/negative sandwich and what that is being held by when getting the exposure and how hot that light source is getting the glass.

Are you using a contact frame or vacuum frame? Backing the paper with another non porous material will help keep the moisture in the paper. Do your images show much image when you pull them out of the contact frame? No image can be an indication of very low RH in the paper. It can also be caused by the type of Ferric Oxalate being used. I ran test with B&S powder, Formulary Liquid, my liquid, Brian Miller's liquid, and some of Jeffrey's powder. While there was a difference in print out (this is with FO not AFO) I was hard pressed to find a direct correlation to speed, but there were differences in print color.


Eric Neilsen