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Similar to how one can use baking powder to fill/accelerate CA glue, which, as far as I'm aware, works because the baking powder neutralizes acids in CA glue, and adds physical "body" to it, there seem to be ways to thicken epoxy-based adhesives, e.g. to make them fill gaps easier and not run down whatever you're gluing.

What I've found from my own research are things like microballoons and colloidal silica, but those are hard to find online. As a "hack", it seems like you can use talcum powder (i.e. most baby powders), but I can't find why specifically talcum, and what makes it different than colloidal silica or baking powder in this application. Additionally, I'm wondering how it would change the adhesive properties of 2-component epoxy glue.

Thank you for your time!

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  • Like adding flour to a stew.
    – Solar Mike
    Oct 31, 2021 at 9:15
  • Recent studies indicate that you might want to stick to "not talcum power" based on asbestos contamination...microballoons are easy to find at any epoxy supplier, generally, IME.
    – Ecnerwal
    Oct 31, 2021 at 11:17
  • Most "talcum" powder these days is IIRC corn starch based. Oct 31, 2021 at 12:08
  • It seems like the question itself may be better suited for [cemistry.se] than Home Improvement since you're asking "how it works", not "does it work", or "is it OK to use".
    – FreeMan
    Oct 31, 2021 at 13:20
  • What is more commonly used as filler is diatomaceous earth. It is silica and rather inert. Various products like paints will show it in contents. Oct 31, 2021 at 15:52

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This answer is a frame challenge addressing "hard to find online".

West System has a perfectly fine variety of epoxy fillers. They are available through a variety of channels and are very reasonably priced. I've never had any trouble finding it locally (certainly any marine shop/chandlery will have it), but I just checked Amazon and yeah... and the seller is Amazon itself, which indicates Amazon thinks it's a popular product and isn't leaving it to the third-party Marketplace.

Given the ready availability of items actually made to be epoxy modifiers, I feel no need to get all Mr. Wizard with improvised products.

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  • I did find the West System colloidal silica, but unfortunately, it doesn't currently ship to me from Amazon, and other places only for unreasonable prices. I've decided to order the more accessible microballoons for "it'll be good enough" reasons and will ask my more theoretical question about the fillers in the chemistry stackexchange. Since you're the only non-comment answer, and because the link to West Systems might help someone else, I'll accept it as having solved my problem. Thank your for your reply!
    – Ben M
    Nov 1, 2021 at 6:47
  • Excellent response, @BenM! You're doing much better than most new folk.
    – FreeMan
    Nov 1, 2021 at 16:17

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