GSRW miniature Acid Proof Funnel 2003 A hand turned wood shape was used to make the plaster production mold. 

Original Red Wing Union Stoneware Co. Acid Proof Funnel 1907 - 1936.

White-Glaze A grayish-white firing glaze produced from a mixture of clay, feldspar and zinc oxide, among other ingredients, better known as zinc glazes,  supplanted salt-glazing just before the beginning of the twentieth century.  Their clean, white appearance was a perfect canvas for applying advertising logos, trademarks and decorations using rubber stamps before firing.