You can easily test various mixes to see how they behave at different temperatures. Adding more Damar Resin and / or harder waxes like Carnauba to your mix raises the melting point but it also makes the mix more brittle. If you work in rigid surfaces that are cradled so they won’t flex you can go pretty hard.
https://www.encaustic.com/techniq/fineart/fineart_recipes/fineart_recipes.html
The harder wax mixtures are of course harder to work with when it comes to scraping / scribing etc., so you may need to warm them up for those techniques. They are also less “sticky” so you need to be sure to fuse the layers well.
Make a test panel and put it in the warmest place it might sit for an extended period and see what happens. Direct sun of course is to be avoided. I put a warning on the back of each piece so that the buyer won’t leave it in a non air conditioned car when transporting it, or a hot location for extended periods. You can test your medium to see at what point it starts to soften and put that temperature on your warning label.
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