Can I use 1 Pete plastic mold for resin casting?

I have a large 1 Pete plastic mold and I wanted to know if I can use it with epoxy resin to make a tile piece? I don t want to waste a lot of resin before finding out if it s ok to use

1 Answer

  • 4 years ago

    Do you mean "#1" recycling number, or PET/PETE plastic (polyethylene terephthalate)?

    That type of plastic isn't as heat resistant as some other types of plastic, and can shrink at somewhat lower temps (e.g., in a dishwasher).

    The type of plastic that's usually used for resin is:

    ....#2 (HDPE, high density polyethylene) ...those are purchased molds, or often used for containers for milk, juice, some water, yogurt, film containers, grocery bags, gasoline tanks, detergent bottles, some toys)

    That type will create the clearest castings, and no release agent is required.

    ......these cloudy-plastic molds can often be purchased where resins are sold (polypropylene or polyethelene)

    ......Tupperware and RubberMaid containers are also made from HDPE

    Plastic molds are easily scratched though (which will show up on resin surface as tiny scratches and/or cloudiness) so don't scrub to clean, or wipe dry (air dry)

    Resins also won't stick to plastics like sandwich bags (think those are #4, LDPE, low density polyethylene), but their heat resistance probably isn't as high.

    (All resins create heat once their two parts are mixed together, some more than others and shallow pours more than deeper ones strangely, I think, so some level of heat resistance is necessary in a mold, etc.)

    Silicone molds are also excellent (highly heat resistant, and no release needed). those can be purchased or molds can be made at home with 2-part silicone mold making materials (like Easy Mold).

    You can read more about using epoxy (and polyester) resins, both in molds and in permanent "cells" of various kinds, if you're interested, on this page of my site:

    (under the category called Epoxy Resins, begin with the subcategory "Preparing, Sealing, and Mixing" and go down through "Casting" sub-sub-categories)

Still have questions? Get your answers by asking now.