Summer is here and it is HOT here in Texas! High temperature can have devastating effects on your molding and casting. RTV or "room temperature vulcanizing" materials are formulated for use at around 70-75 degrees Fahrenheit. Higher temperatures will accelerate RTV materials whereas low temperatures will either retard their cure or, in extreme cases, cause them not to cure at all.
Unused, liquid components stored and used at 90F+ will behave as though an accelerator has been added. Easy Flo 60, 120, and Clear have a working time of 2.5 minutes at 75F. At 95F, they will set up mid-pour as the working time will be reduced to less than 1 minute. PlatSil Gels, also fast setting at room temperature, will also be virtually unusable at high temperatures.
If your silicones, urethanes, or resins are stored in an area that gets significantly hotter than room temperature (75F), make sure that you allow the components to cool down to room temperature before use. If your work area is hot, you can offset this somewhat by storing your materials in a cool area and only bringing them into the warm shop environment for use. Be aware, a hot work area may still act as a mild accelerator, resulting in more air entrapment and shorter working time.
If the heat is unavoidable, adding a retarder to PlatSil or switching resins may be the only way to avoid a rapid, "snap" set. 71/73R retarder may be added to PlatSil silicones to extend the working time. Easy Flo 60 does not have a retarder additive, but you can switch to the slightly slower Easy Flo 95.
Luckily, hot weather will not permanently alter the cure speed of a given material. Just make sure you allow your liquid components time to cool to room temperature and the usual physical properties will return.
Be sure to read your data sheets before starting a project and avoid cure issues by storing your molding and casting supplies at or around room temperature.
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