Hello! I have run into a problem making casting slip. I have been using a tried and true recipe from an instructor several years ago for a casting slip that calls for grolleg kaolin. I mixed up a new batch and did not realize that when I said grolleg, the guy at the sales counter heard EPK. I thought when I saw the bag that perhaps it was from a different supplier so added it. Realizing that it was not at all the same in color and substance, I did some quick research and saw that it is essentially the same but will shrink a little more than the grolleg. Okay, cool. I can deal with that as I am experimenting with slip casting anyway, so I added it as I was in the middle of it all and did not want to put it all away again. But then when I got home I looked in the Andrew Martin book he said it will not work at all because it holds on to the water and will cause the casting to have a thin wall and be brittle.
So now: do I toss my batch and spend another $100 on supplies or would you attempt some sort of save? I did cast one small plate as a test and I didn't notice any extra brittleness, though it did take longer to cast. It will be going through bisque fire in the next day or so, which might help me decide. The only other thing that I noticed is that it immediately starts to settle and turn into oobleck on the bottom of the bucket. The specific gravity is 1.6, which is a lot lower than normal. I was trying to decide whether to let it evaporate for a while and then add some Darvan or SS (though I made it with a bit of soda ash which I have heard doesn't play well with Darvan). Or maybe I just start over and learn to look more carefully at what they are loading in my car.
Thanks in advance for any advice or knowledge you can impart.