What are the set, demolding and curing times for FMG?

Article courtesy of Smooth-On, Inc.

Set time is the time when the slurry loses workability and begins to stiffen and set - also referred to as working time. Using a typical alpha product formulated for this process, set time will be 20-30 minutes. Set time can be shortened with accelerators or lengthened with retarders. Without acceleration, parts made with FGR-95 are normally demolded after 60-90 minutes. While the parts may be strong enough for demolding in 60-90 minutes, they will not have fully cured and will still be "green". This is an ideal time to do any finishing or chasing of edges. A demolded part will begin drying immediately after removal from the mold. The rate and degree of final curing will be dependent on ambient weather conditions. Hot/dry will cure faster than cold/wet. In typical conditions of temperature and relative humidity, full cure can take 5 to 7 days. For larger pieces such as architectural moldings, orientation or support of the piece while curing is very important. All gypsum based materials are subject to cold creep. If the pieces are not stored properly while curing, warping or bowing might be cured into the piece.


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.