High Calcium Semimatte 1 (Mastering Glazes)
Recipe
Notes
While "Waterfall Brown" is about movement and "Waxwing Brown" is about a waxy feel, HCSM 1 is all about the classic, soft, "eggshell" finish. Key Properties • Visual Appearance: A smooth, buttery, semi-matte surface. • The Science: The matteness comes from Calcium-Silicate crystals that grow as the glaze cools. A controlled cooling cycle ("down-firing") is needed to give the crystals time to form. • Surface: It is often described as having an "oily" or "buttery" feel rather than a chalky one. • Durability: Resists leaching and staining—making it safer for food surfaces. Likes (Pros) • The "Feel": It is pleasant to hold,. • Reliable Color Canvas: It accepts colorants like Cobalt (blue), Chrome (green), or Manganese (purple) with clarity and soft, variegated transitions. • No Running: It is a "stiff" melt, staying put and enabling clean lines between different glaze colors. • Resistant to Staining: The tight crystalline structure of HCSM 1 makes it easy to clean. Dislikes (Cons) • Cooling Sensitivity: If your kiln "crash cools", this can come out looking glossy rather than matte. You must be willing to program your kiln to slow down between 1900^circ F and 1500^circ F. • Cutlery Marking: Because the surface is composed of tiny crystals, it can sometimes act like very fine sandpaper against metal. • Application Thickness: If applied too thick, it can occasionally "crackle" or crawl in corners. If too thin, it loses its buttery feel and can look a bit "stony" or dry. • Variegated Slate Blue Variation: It is notoriously picky about the specific batch of Red Iron Oxide and Rutile used; shifting from a beautiful blue-grey to a muddy brown.
Description
From page 86 of Mastering Glazes book