Cyanotype blotches

I'm currently testing and diddling around with my first Ware's New Cyano
kit. My first test went fairly well. I used a new foam brush to coat a 4X5
sheet of Bienfang No. 538. Sandwiched my digi step wedges (and threw a
stouffer 21-T on top for good measure) and baked the goods in my (brand
spankin' new {blowing on knuckles}) UV light box for 20 minutes. The test
sheet, once washed, dryed to a beautiful blue -- but way way too much
exposure. My Stouffer wedge was readable only from about steps 5 to 9.
Today, I tried test number two on a piece of Rives BFK as well as Bienfang
again. This time instead of air drying the sensitized paper for an hour I
put it in the print dryer for 15 minutes at 125F. Seemed to work. I reduced
my UV exposure to 6 minutes. The results were puzzling. First, I noticed
5-10mm blotches all over the papers like salt sprinkles. The Beinfang's blue
was OK (not as nice as the initial test) but the sensitiser practically fell
off the Rives BFK paper during the wash rinse -- today using a kodak siphon
tray running slooowly. I use a 10ml syringe fitted with an extension tube to
draw my cyano solution from it's bottle and a separate dedicated eye dropper
for adding the clearing agent. I drew 2ml of sensitiser and used one drop of
clearing agent. It's possible that there were water droplets in the syringe
from being cleaned after the first use, or possibly water in the sponge
coating brush which I also cleaned with water yesterday. What other sources
of contamination are common in this process? Could heat from the print dryer
cause problems? 125F doesn't seem very hot. BTW the blotches were first
evident after the initial coating of sensitiser had dried and I examined the
paper coming out of the dryer, I thought maybe they would go away but
development made the problem quite obvious. Also on the second test I
"worked" the brush a little longer and harder into the paper probably making
at least 4 or 5 passes to ensure the sensitiser was "in" the paper.
Received on Wed Feb 16 23:22:16 2005