Zinc Semimatte Glossy Base Cone 6
Recipe
Notes
While the authors of Mastering Glazes often prefer calcium-based mattes for stability, they included this zinc-based version for potters who want the buttery "low-luster" surface that zinc provides. Key Properties • Visual Appearance: A soft, muted teal or sage green. A semi-opaque with a soft, eggshell-like glow. • Surface: It has a "stony" semi-matte texture. Because of the Zinc Oxide, it develops a micro-crystalline surface that feels smooth to the touch but lacks a reflective glare. • Mechanism: The "Sea Green" hue is typically achieved through a combination of Copper Carbonate and sometimes a hint of Rutile or Iron Oxide to soften the copper's natural "electric" green. • Stability: It stays where you put it and doesn't run, making it very safe for the kiln. Likes (Pros) • Sophisticated Finish: The semi-matte surface makes the piece feel more like a natural stone object. • Great for Sculptural Forms: Because it doesn't run or "pool", it holds the crispness of your clay work. If you have sharp edges or subtle finger marks from the wheel, this will cloak them. • Pleasant Feel: Like the "Waxwing Brown," this is a "pet-the-pot" glaze. The zinc creates a surface that is very satisfying to hold, making it ideal for the exterior of tea bowls or tumblers. • Reliable Fit: Zinc mattes fit standard stoneware bodies, meaning you are less likely to deal with the crazing issues, like those found in the "Raspberry" recipe. Dislikes (Cons) • Marking: If you use a stainless steel knife or spoon against the surface, it may leave a dark grey streak (like a pencil mark). For this reason, it is often used on the outside of bowls and the inside is lined with a glossy. • Color Sensitivity: Copper-based greens can be sensitive to the kiln environment. If fired too hot, the green can "wash out" or turn a bit metallic/black in spots (a phenomenon called "copper wash"). • Application Thickness: If applied too thin, the glaze can look "starved" and dry, like a chalkboard. It requires a confident, medium-thick application to get the semi-matte "sea green" depth. • Not Acid-Proof (Relative): Zinc-matte glazes are slightly more susceptible to "etching" from strong acids (like lemon juice) over many years compared to their high-gloss counterparts.
Description
From page 98 of Mastering Glazes book