This recipe can be doubled—it makes about 1-plus quart. Originally, this recipe came from Lillstreet Studios in Chicago, Illinois. I use Mason stain 6600 for black, but you can use any color Mason stain to tint your slip. The color will be paler than the undiluted Mason stain because you are adding it to a large body of white. For black, I use 9% but the original recipe called for 5% colorant. I believe too high a concentration of certain colorants can cause bubbling under the clear glaze.
I like this slip mixed to the consistency of thick cream, but you can make it thinner at any time by adding water. When you make it, it may take a few hours for the deflocculant to work completely and it might seem too thick initially, but I recommend waiting until the next day to adjust the consistency by adding water.
I do not use this as a dipping slip, but if thinned enough you could. I like to use natural bristle brushes to apply it to the surface of my pot and if it’s thin, wait until the shine is off and put on an additional coat.
Since this slip is porcelain based, it perfectly fits a Grolleg porcelain body. It will also work on all sorts of stoneware but I recommend applying it as soon as you can so that the slip doesn’t shrink and crack off—that can happen if you apply it to a near-dry or bone-dry stoneware clay piece.
This slip works well from cone 6 to cone 10 but becomes richer as firing temperatures increase. I love this slip in atmospheric firings, although it can run and turn blue if it’s really blasted.
This recipe was shared by Glynnis Lessing in the December 2023 issue of Ceramics Monthly.