For the recommendation of not sandblasting the surface, you can always use a Kleenex with some of the porcelain laying in the bottom of your porc build up drawer. Otherwise, put a little normal pfm/emax etc porc on a pallet and dab your Kleenex into some water, pick some of the porc. up with the Kleenex, and scrub the surface then steam clean it, will take care of the surface tension. It's a lot cheaper than using InSync glaze paste.
Man with all you guys talking about ways to relieve tension I came up with a couple of other ideas myself but realized I'm on the wrong type of forum to mention those...Bahahaha