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Recycling Old Molds into New Molds

March 5, 2019

Sometimes our silicone molds don’t turn out the way we hoped. Sometimes we only need a few casts from a mold and then it spends years gathering dust on a shelf. It feels wasteful to throw out a mold after all the hard work and cash went into it but there’s nothing else you can do, right? Wrong! In this post, I’ll show you how you can recycle an old mold into new mold, saving money on silicone and making your block molds more cost efficient.

You can also watch a video of this project here,

Materials needed:

  • An old or unusable silicone mold of the same type of silicone you wish to make the new mold from. Use tin catalyzed silicone for new tin catalyzed silicone mold or platinum catalyzed silicone for a new platinum catalyzed mold.
  • AeroMarine Products 128 Pourable Silicone RTV Rubber (That is what I’m using, see above)
  • Scissors or sharp fixed blade, like an X-Acto knife.
  • Mold box (I used cheap tupperware)
  • Scale for measuring the silicone
  • Plastic mixing/measuring containers and utensils
  • Gloves
  • An object(s) to mold

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

The first step is to chop up your old/unusable silicone mold. I usually cut it up into small cubes because I find that easiest. So grab your scissors/X-Acto knife and get to it, CAREFULLY. This is usually a little time consuming, unless your mold is pretty small. Put the chopped silicone into a plastic bag for easy storage. If you work with more than one type of silicone, label the bag with the type of silicone it contains.

Now, we’re ready to recycle silicone into a new mold! Get your mold box and anchor your part to the bottom of the box.

Wherever there is space that will be filled with silicone, arrange the chopped silicone to fill it up. Don’t put the chopped silicone right up against the part(s) because you don’t want to obscure any detail. You can stack/layer the recycled silicone to fill more space as well.

Next, weigh, mix and pour the new silicone. For more detailed instructions on this process, check out this blog post,

You can also watch this video,

I like to pour onto the recycled silicone, since it makes me pour more slowly which means less air bubbles.

Let the silicone cure completely, in this case 16-24 hours, then de-mold.

That’s it! The new silicone bonds to the recycled silicone, allowing you to use less new silicone and saving you money!

If you have questions about this project or any other project, drop us an email at [email protected] or give us a call, toll-free, at 877-342-8860.

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