Brand : REFSAN
Price : 10,67TL

CMC GUM (Carboxymethyl Cellulose)

Carboxymethyl cellulose (CMC) or cellulose gum is a cellulose derivative with carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone. It is often used as its sodium salt, sodium carboxymethyl cellulose.

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 settings benefit greatly from the addition of gum. Single layer cover glazes that have natural hardening properties (i.e. from 15% or more clay) do not need gum. Gum is an important addition to stain mixes that are applied over-glaze by stamping or painting.

In dipping glazes, gum can act as a suspending agent (but this is seen as a side effect, there are much better ways to suspend slurries). CMC gum makes slurries stickier, more difficult to clean off tools and containers. CMC-containing slurries do not respond to gelling (via epsom salts or calcium chloride) so the main way to control the thickness is by adjusting specific gravity. This makes it difficult to tune the rheology of dipping glazes that need CMC gum (to enable them to handle over layering). The slower drying makes it difficult to achieve an adequate glaze thickness and prevent drip marks during dipping.