Hi, My Polaroid 665 pos/neg pack film has arrived so I am eager to make some 645 polaroid negs this weekend I also have the chem for making a negative clearing and hardening combo solution. This way I only need one clearing container in the field. This is Sodium Sulfate (yes sulfate not sulfite) and Potassium alum. I have the formula and the chemicals (they are in a very fine powder form). So, what temp should the water be, and I'm assuming I can mix them both at the same time? Also, are these chems highly toxic or anything to worry about? Thanks!