Slipcasting From My Stoneware Body

[Riorose]

Hello, writing from Europe where i do not have access to American products. I am starting to use a really nice German made white stoneware and i want to make some paperclay and some slipcasting slip from it. So far I managed to deflocculate with Sodium carbonate and sodium silicate and I have a specific gravity of 1.75-1.80. it looks Ok but it sure takes a long time to cast. i think I had it in my gesso form for 30 minutes or more and only had a thickness of 1/8 inch. Is this normal? I am accustomed to a porcelain slip that sets up so rapidly, I can have a nearly solid form in that amount of time. I ended up doing 2 coats and barely got beyond that thickness. Should I let it stay in the form for 45 minutes or an hour? should I try more deflocculant or water, however it seems similar to my commercial porcelain slip.

 

Thank you