This should be in every assortment of artists' tube colors, it being used by them as a drying medium. It is prepared as follows in quantity:
Heat in an enameled kettle 12 pounds raw linseed oil with 10 ounces of fine litharge for 30 minutes, stirring with a glass rod all the time, then set aside to cool and settle. After 24 hours decant the oil off the sediment and filter it. Also melt on a water bath 4 pounds gum mastic in 8 pounds gum spirits of turpentine and when the gum is dissolved, set the kettle away over night, then filter the solution and stir it into the oil. When thus well mixed, set the material in a cold place, during the winter time, and in summer keep in a refrigerator. Fill tubes only, when called for.
Mix well together, one volume concentrated solution of white sugar of lead, two volumes bleached linseed oil and two volumes of gum mastic, dissolved in turpentine.