Originally Posted by Kerik
Thanks for your kind words concerning my work.
F/STOP: I'm making an educated guess here: f/256 - f/384 - could be wider. My intial tests were at 15 mins and turned out to be good negative exposures - the Ambrotype exposures were between 4 - 6 mins. This is all in BRIGHT SUNNY weather.
KEEP THE PLATE WET: I wrap the back in a wet, cold cloth (insulating/almost freezing it), I keep the plate FLAT, collodion side up and I DO NOT wipe excess silver from the plate when pulling from the bath. Using all of these methods, I can go (easily) 15 minutes in the winter/cool weather.