A fine grade of Castor Oil product used to protect and give proper finish to surfaces that have no oil in them.
To use: Here's an example: You have just attached a latex or foam latex appliance to your face and you wish to color it with regular creme foundation. First, stipple a thin layer of castor seal over the entire piece, then powder that down. Next, apply creme foundation over the piece. By doing so, the creme base is less likely to get the chalky look it would take on if the foundation were applied to an untreated piece.
Note: This two step process may be precluded by using Rubber Mask Grease make-up, which is a castor oil based make-up.