I put the finely rolled clay back in a bowl and add water to cover the clay completely. If after several hours all the water is absorbed, add a little more water. At this point resist the urge to stir the mixture since this increases the amount of lumps. The idea is to end up with as smooth a mixture as possible.
mason stains for colored slips. To mix in mason stains to a pint mixture (about a cup of slip) I start out with a teaspoon of mason stain and wet the mason stain in a small glass bowl with a bit of water. Then I add that to the container of slip till I think the color is good to my eye. Later I put a piece of tape on top of the jar of stained slip noting the amount of stain I have added for that particular color. For more details on mason stained slips click the link to Slip Slop Stain and Mixing Mason Stain Slips.