How to understand the Closed-coat and the Open-coat in the abrasive?

Coated abrasives are generally manufactured in two levels of abrasive grain surface density. Closed-Coat The abrasive grains completely cover the coated surface of the backing. The greater number of abrading points per square inch causes faster stock removal during use and produces a better finish than open-coat.

Closed-coat is recommended where loading is not a significant problem. Open-Coat The abrasive grains cover approximately 50% to 70% of the coated surface of the backing. Open-coat abrasives are the best choice where clogging or filling of the abrasive surface would otherwise be a problem. They offer greater flexibility, but are harsher cutting and do not provide as good a finish as closed-coat. Wood, soft metals and fiberglass sanding are typical applications for open-coat products.