How long does Accu-Cast alginate take to cure?

Article courtesy of Smooth-On, Inc.

Our alginate product names give basic information about their alginate setting times. The three number sequence refers to the setting time at a particular water temperature. (For example, under ideal conditions, FaceGel (590) alginate will set in about 5 minutes when using 90°F water and BodyGel (880) sets in about 8 min. with 80°F water)

  • BabyGel (380)....... 3 minute set w/80°F water
  • HandGel (570)....... 5 minute set w/70°F water
  • FaceGel (590)....... 5 minute set w/90°F water
  • BodyGel (880)....... 8 minute set w/80°F water

We test our alginates during manufacturing so they perform to these standards (+/-5%). We test under controlled conditions (low humidity and 70°F air temperature with purified water).

Rarely will you have the luxury of using our products under such conditions. Here is a list of factors that can affect the alginate setting time (in order of the magnitude of their effect):

  1. Water Temperature....... Warmer water will speed the setting time of alginate and cooler water will slow it. (For a graph of setting times vs. water temperature, look below.
  2. Mixing Ratio....... Thicker alginate sets faster, thinner sets slower- all else being equal.
  3. Air Temperature....... Air temperature will affect how quickly the alginate will cool during and after mixing- same "warmer/faster, cooler slower" effect, however layup molds will be much more affected because of the larger "surface area to volume" ratio. Spread thin, it will be more affected by air temperature and evaporation than a bucket mold.
  4. Humidity....... Since evaporation off the surface of the alginate will cool the mass, lower humidity will increase evaporation, cooling the mix and slowing the set. Higher humidity will lessen evaporation, allowing the alginate to stay warmer which will shorten the setting time.
  5. Chemicals in the water....... In general, our recommendation is, "If you feel fine drinking your tap water, then its OK to use to mix your alginate". If you filter your drinking water or there are noticeable odors from your tap water, best to use bottled water. The cheap stuff is fine. We have no idea what effects your tap water might have on the setting time or any other working property of your alginate. If you're having problems, please feel free to contact us.


If you are working in a non-standard environment, like outdoors in Houston, TX in the summertime, you know it will be very hot and humid. These are both factors that will shorten the alginate setting time. Either use cooler than recommended water or choose a longer setting alginate for your project.


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.