Cone 6 slip on low fire clay?

[Frenchie Argent]

Is it ok to use cone 6 porcelain slip on a lower temp clay? The lower temp clay is dark and I want to have a white layer on it.

[Bill Kielb]

Very good chance it won’t work.at all. You might want to use a lowfire slip. Here is a recipe from Alfred University that might prove useful for you. https://glazy.org/recipes/85897
 

[Chilly]

LIke using the wrong cone glaze, they could be different COE, and expand and shrunk at different rates

Best result = it works.

Worst result = after firing, slip explodes off clay when you least expect.

[Min]

@Frenchie Argent, is this for the same project as you posted about in the other thread where you are putting slip on bisqued tiles? Linda Arbuckle has adapted slip / engobe recipes from Daniel Rhodes which have variations for both leatherhard clay and bisque, her pdf article here and her adapted Rhodes recipes below. If you are putting slip on leatherhard clay try and get it onto the clay as soon as possible to avoid cracking problems. If you want white do add the opacifier, 10% should give you a good white for covering dark clay but this can be increased if necessary.

[Frenchie Argent]

Yes Min, I applied cone 6 porcelain to a commercial low fire tile and it didn’t seem to fit properly....

[Min]

13 minutes ago, Frenchie Argent said:

 I applied cone 6 porcelain to a commercial low fire tile and it didn’t seem to fit properly....

Shrinkage for slips going on leatherhard is going to be higher than shrinkage for slips going on bisque. If the shrinkage is too high the slip will crack therefore shrinkage needs to be reduced. This is done by calcining some of the clay content of the slip. Have a look at the differences between the slips for "wet" and bisque, see how there is calcined clay in all the recipes for bisque? This is because calcined clay has shrunk during the calcining so the shrinkage of the slip will be decreased which should reduce cracking problems. Other issue for slips applied to bisque is getting them to stick to the clay. This is where the soda ash comes in, it melts at a low temperature therefore aids in getting the slip to stay on the pot. Don't skip the soda ash, it really is necessary for bisque slips. (dissolve it in very hot water before adding the rest of the ingredients)

edit: to calcine kaolin just include some in your next bisque firing.