Alkaline Base

Date: Spring 2023

Creator: D. Reed

Temperature: Cone 04 - 01

Atmosphere: Oxidation

Recipe:
Ferro Frit 3110 65%
Soda Ash 15%
Gerstley Borate 9.0%
EPK 5%
Silica 4%

Bentonite 2%

Straw Yellow:
Manganese Dioxide 10%
Red Iron Oxide 11%

Dark Manganese Purple:
Manganese Dioxide 10%
Cobalt Carbonate 1%

Notes:

Based on, or rather a continuation of, Lisa Orr’s Honey Amber Glaze. Glaze fires consistent from cone 04 - cone 01; glossy surface with slight crazing. The base glaze with or without manganese dioxide takes color well and runs quite a bit when dipped twice. Brush application requires 2-3 coats whereas dipping/pouring glaze needs only one, even coat. 

After periods of time, however, this glaze appears to form white, powdery films in small spots. I believe this could be due to the soda ash present in the glaze, and am unsure as to if this glaze is food-safe. This is not present on all glaze test tiles but is easily wiped off.

On majolica and Reed’s 4:3:5:10 Base Glaze, this glaze is a stable and vibrant overglaze. The Alkaline Base displays some slight porosity or pin-holing texture but is not unpleasant in my opinion. Leach testing should be considered before using this glaze on functional vessels.