High-Performance Joint Compounds with Specialty Minerals Ground Calcium Carbonates and Talc

During construction of an interior wall using gypsum board or wall board, a high-quality tape joint compound helps ensure a smooth, good-looking job. Joint compounds, also called taping muds, must effectively fill the spaces between sheets of wallboard, conceal the edges of the joint tape, and easily sand to a uniform surface.

Minerals Used in Joint Compounds
Ground calcium carbonate (GCC), or ground limestone, is the most widely used mineral in joint compound formulations. Also used is ground dolomite, a calcium magnesium carbonate. Ground calcium carbonate adds value with its high brightness and its reinforcement properties in the finished product, as well as serving as a cost-saving filler. Talc is a second mineral used in joint compound formulations, as its platy particles help prevent cracking and yield an easy-to-apply product with a smooth surface finish.

Joint compound products are typically filled with GCC or ground dolomite at about a 70 percent level, up to a maximum of 80 percent. Recent trends lean toward more lightweight formulations, where only 30 to 40 percent filler may be used. Carbonates used in joint compounds are usually 200 to 325 mesh products with top sizes (largest particles) of 44 to 75 microns.

Talc is used in formulations at a loading of 5 to 15 percent. Talcs must be bright for joint compound use and control of the product’s top size is crucial to prevent streaking during application. Suitable talc particle sizes for joint compounds range from 7 to 8 microns in median particle size with 200 or 325 mesh as the top size.

Specialty Minerals Products for Joint Compounds
Specialty Minerals Inc. (SMI) is a leading supplier of minerals to joint compound manufacturers in North America. Our GCCs, dolomites, and talcs are carefully processed for excellent control of particle size and brightness and exhibit unmatched lot-to-lot consistency.


When formulating a joint compound, choose from among these SMI products:


All SMI plants are ISO 9001 certified and processing is tightly controlled to produce minerals with uniform particle sizes and particle size distributions.