Soft Edge Stopout

 
This is similar to the Ruth Leaf recipe, but has some methyl cellulose added to increase the permeability of the ground.  Methyl cellulose seems to be a good agent for controlling the permeability of white ground. You can usually find some at any place that sells wall paper, since it's used as a wall paper paste. It's usually called something like "Clear Cellulose Adhesive", and comes in the dry form which is small flakes.  You can also get it at the drug store, in the form of  KY jelly, which is a lot more expensive.

To use the dry flakes, prepare a stock quantity of approx. 2 level teaspoons of flakes in a cup of cold water. Use cold, not hot water. Put the water in a jar, and gently swirl it as you sprinkle the flakes into the water. You can swirl and stir until you have a fairly even mixture. Let it sit for a while; preferably overnight until the flakes are dissolved and you have a clear gooey gel.

This "Soft Edge Stopout" is equal parts of this methyl cellulose gel and Ruth Leaf recipe white ground.


Notes on White Ground

The Ruth Leaf recipe calls for Ivory Snow granules, which have been off of the market for years.  I substitute by grinding up Ivory soap bars in a grater. I then use about half as much of the ground up bars as is called for with Ivory Snow, since the ground up bars are about twice as heavy per volume as the Ivory Snow granules.  Ingredients in these recipes aren't highly critical. If you find your white ground is too greasy (fouling your brushes, etc.), add more soap.

The Ruth Leaf recipe also calls for titanium white pigment, which works fine and is generally best. However, if you use mostly titanium white and a small quantity of zinc white you get a ground with a nicer consistency. The zinc white acts as a dispersal agent, and helps keep the ground homogenized. Titanium pigment doesn't have much effect on permeability, but zinc white significantly reduces permeability.

This ground tends to be a bit grainy, but can be made smoother by mulling. It tends to be runny when first mixed, but thickens when allowed to sit in a container.