Cardstock (doesn't seem to work on black-I had to try it for myself-and it didn't work.)
Put 1/2 cup of Epsom Salt in a hot tolerant bowl. Add 1/2 cup of boiling water and stir until the salt crystals are dissolved. Use a paint brush to paint the entire surface of the cardstock and cover well.
Do Not go back and try to add more after it begins to dry-it will ruin it. I think it is best to let it dry naturally and plan to make it the first thing we do at my upcoming technique class. We can then finish the card last of all. Be patient....and happy stamping!
Consider trying it for a crystalized ice look too. But....don't use Bashful Blue-it DID NOT work. Marina Mist worked though.