The term CMC is generic and refers to organic sodium carboxymethylcellulose. Gums are used in ceramics to harden unfired ceramic glazes. This makes for safer handling of ware, better adherence to the body, slower drying (thus better brushability). CMC gum also reduces drying shrinkage and enables multi-layering without flaking or cracking. Highly fritted glazes (lacking clay content) used in factory …