Thank you for your replies bros and sis! Oh my yes! This is the one! I tried using 2 clay bodies but the effect is wispy at all, therefore is there any method I could try with?
I don't know the exact method those people used but if I was making those I would take 2 casting slips (made from the same clay), of what ever colours and pour a slowly rotate the 2 slips into the mold. Coating the inside of the mold to the top to create a shell of slip. Once that had set up a little I would then pour an unstained slip into the mold and let it set up until wall thickness is adequate then dump out the mold of excess slip. I'm guessing the excess slip would be slightly stained so might use that for subsequent batches of stained slip. You could fill the mold entirely with a couple stained slips but would land up with a heck of a lot of waste slip that would have to be used up.
Oldlady, were you referring to Nemadji Pottery?
Is it called marbled slip cast?