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I have read in several places that adding fresh silicone over cured one will not work, as the new silicone will not adhere to the old.

The question is: if I create some object of epoxy resins, can I repair dents by adding more (fresh) epoxy?

virolino
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1 Answers1

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In my experience fresh epoxy will bond with already cured resin just fine.

  • Both the cured and fresh epoxy should be the same chemicals. I have no experience with layering different types of resin.
  • Given that the surface of the cured resin is clean (no dust or oily residue) and both batches have the same color you cannot see the individual layers after the fresh resin cured.
  • Given the first batch of resin cured right (the resin to hardener ratio was right and it's not still soft or sticky) I was never able to seperate individual layers of resin without breaking the object. You cannot "fix" a batch of resin that doesn't cure because of wrong mixing ratios by pouring more resin on top. You can only stabilize slightly bendy resin.
  • If you expect the joint to come under tension, you should roughen the cured surface with coarse sandpaper. This gives the fresh resin a bigger surface to bond to but will become invisible if you remove the dust before pouring.
  • You should keep surface tension in mind. Pouring fresh resin over only part of a cured object creates a visible transition and the fresh surface will reflect light differently because surface tension pulls it into a different shape. I highly recomment covering the entire surface of a cured object with a thin layer of fresh resin to repair dents or holes. Pour enough resin that the surface tension cannot pull the fresh resin away from corners or high edges (happened to me several times)

When I craft with resin I often cover objects in several thin layers of epoxy. In videos you often see people grinding and polishing their epoxy jewelry to a shine in a long process. If you don't need perfectly even surfaces, you can pour a thin layer of epoxy on top instead and archive a finish that's clear and shiny without the trouble of polishing.

Elmy
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  • Thank you for the answer. I planned to create a larger object by crating smaller parts, joining them together, and then seal the joints. Same resin, same chemicals. Your answer hints that it is doable. – virolino Feb 12 '20 at 06:32
  • @virolino I added a bullet point about roughening the surface with sandpaper. "Larger object by crating smaller parts, joining them together" sounds like the joints will be under tension by the weight of the object alone. I don't know how stable those joints will actually be. All I ever created from resin is jewelry where the object's weight is negligible. – Elmy Feb 12 '20 at 10:30
  • I have in mind adding some kind of reinforcement if I will go the joined-parts way. But your hint with sandpapering as a preparation step is very good. – virolino Feb 12 '20 at 10:54