What does the number associated with each foam represent?

Article courtesy of Smooth-On, Inc.

Each Smooth-On foam has a number associated with it that represents the free-rise density or cubic foot "yield-per-pound" of the foam. Larger numbered foams have a higher density, whereas lower numbered foams have higher expansion rates.

For example, if you poured Foam-iT! 5 liquid into a cube measuring one cubic foot and the foam expanded to 12"x12"x12", it would weigh 5 lbs. If you pour Foam-iT! 10 liquid into the same cube, it would fill the same space and again expand to 12"x12"x12" (1 cubic foot). However, the Foam-iT! 10 cube would weigh 10 lbs. due to a higher density.


This FAQ article is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Safety Data Sheets (SDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.