Hi again,

You don't actually need twice the amount; you aren't supposed to always use saturated dichromate solutions. If using PD, try to keep the solution strength below or around 10%, with AD the upper (safe) limit would be something around 25%. I never used something stronger than 15% for gum myself - and that was for a short period of testing paper negatives! My usual dichromate concentration is 5%, and the exposure times are around 3-6 minutes with UVBL lightsource - nothing slow here...

Regards,
Loris.