I use corn starch according to the directions in Crawford's Keepers of Light
(i.e., dissolve 5 grams of starch in 80 mL cold water, and add this to
200 mL of boiling water and boil for 3 minutes. I find that one-quarter
of this recipe is about the right amount for a 20x24 print if you brush it
on - 1.25 grams starch in 20 mL cold water, added to 50 mL of boiling water.)
The solution should be used while warm, but "unlike gelatin, starch
cannot be hardened effectively and is therefore a less durable sizing
material, not recommended for multiple-printing techniques."
I practice multiple-printing techniques.