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What process is this? I've never heard about ammonium dichromate being slower than potassium (though I have heard about sodium dichromate being less active than either of the other 2).Quote:
Originally Posted by edwoo11
You need to make sure you account for the difference in molecular weight of the 2 compounds, but I don't have the numbers at-hand to give you.
--Greg
I agree with Greg here, ammonium dichromate isn't slower than potassium dichromate - given the solutions have the same dichromate ion concentration. When mixing by weight/volume, 1g A.D. is equal to 1.167g of P.D. - that is, A.D. is more sensitive per given weight. (Because you'll end up with more dichromate ions per weight.)
Regards,
Loris.
Good to know thanks, I think I read that somewhere, may be this person was mixing less amonium dichromate to get longer exposure times...
nice for me if is the same, if i can have some later... is it cheaper ? because you need twice as much.
I am doing gum prints.
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.