to answer both questions on this list at once, no the alum from
Prochemical is quite different from the chemical used to do
pickles.and it's been discussed a couple of times in the archives.
The Alum I have from Dharma Trading is Aluminum Sulfate. I
believe the concentration is different also. I got the alum out of my
cabinet for pickling and it doesn't say on it what it is. I just looked at
Pro Chemicals' site and it says their alum is Potassium Aluminum
Sulphate, but both are suitable for dyeing and marbling and work
well for either.
For the next person, this is a good site for converting
For dry measurements, it says 2 tablespoons equals an ounce.
Also, as I have found, different companies give different directions,
like for the amount of alum to water or methyl cellulose to water.
I use the carageenan gum from either Diane Maurer or Galen Berry.