Veegum-T is a material used as in glaze recipes and clay bodies. In glazes, it is used as a suspender and thickener. In clay bodies, it is used as a plasticizer. When adding this material to a glaze slurry, it is very imporant that it is mixed with water before adding it to the rest of the materials. Improper hydration and variations in mixing conditions (water temperature, amount of water, time mixing, mixing power, etc) can produce varied results in glazes.
Information gathered from Digitalfire Ceramic Materials Database.