Hi
I’ve been making a load of things (mostly rings) with either epoxy and/or PU resin. Some clear with inclusions and some opaque and some a mixture of the two. My questions concern the finishing of them. I understand epoxy resin isn’t UV resistant so clear would yellow over a period of time. Also, I find that I don’t always get the best finish when using silicone moulds. Therefore I need to coat each piece with a clear coat or a lacquer. I’ve had a look on EC website and forum and have found several possibilities. But which one would be best for my purpose?

1. A resin clear coat. Would I sand the piece then apply this to one side, let this dry then apply to the other side? Can it be painted on without brush marks? Can I then buff it on a buffing wheel?

2. GC50. Does this work on the same principle as a resin clear coat as above? Again would I apply it in sections, can it be painted on without brush marks and can it be buffed on a wheel?

3. I’ve also read on here about a 2 part clear lacquer used on cars. Is this just a general acrylic or is there a specific one that I should be looking for? What does the ‘2 part’ refer to? Would it bond ok with PU and epoxy?

Basically, im looking for the best method for UV protecting as well as achieving a high gloss finish on small jewellery pieces? I know some puritans out there may well suggest going through the sandpaper grits but I’ve tried this and it takes far too long with only barely adequate results?!

Hoping someone can point me in the right direction. Much appreciated. X

Hi Wends,

Sorry for the late reply, we're officially closed over the Christmas break but I'm just checking in on the forum so see if I can help out at all over the break. I can see that Oakmont has provided you with some helpful advice.

UV stability of epoxy resins is a *big* subject with no 100% definitive answers. What I can do though is explain honestly exactly where the chemistry of our products is up to and what my own recommendations would be.

First off, no epoxy resin is 100% UV stable. Some (especially a select number of modern resins) have excellent resistance to UV light. Others, which have not been designed for the purpose or which use outdated chemistry, have very poor resistance to UV light and within a month or less of direct exposure. The best of the modern UV resistant epoxies that we sell (such as ArtResin, XCR and GlassCast) have excellent resistance to UV and show very little yellowing after accelerated UV exposure equivalent to thousands of hours of direct sunlight. These special UV resistant resins do already have the 'blockers' in that oakmont was talking about and so you would not need to (and we wouldn't not recommend that you do) add any further additives to the resin (it is likely to affect their clarity). I would say that for the indoor/occasional outdoor environment of jewellery, you would be extremely unlikely to see any noticeable yellowing of any of these resin systems within a several-year timeframe. Therefore, if you're working with any of these resins then we would not suggest that you would need to coat them in order to provide further UV resistance when you're making jewelry items.

Oakmont mentioned our new casting resin which would certainly be a very good suggestion for you. We actually have two new UV stabilised epoxy casting resins launching in January 2018 (they are running very late and we due to launch months ago but they are now in stock and will be available to buy in January). The product for you would be our "GlassCast 10" which we've developed specifically for smaller creative applications like jewelry. The resin is water clear, highly UV stable (see notes above), self-degassing and cures with a super glossy finish. Pricing will be very similar to our current GlassCast product. We have had samples of this resin in our UV exposure unit since the summer where they have been clocking up thousands of hours in intense UV light and show very little discolouration even in this extreme UV environment.

Another point you mentioned were that you were using some polyurethane casting resin. It's worth pointing out that our Water Clear Polyurethane Casting Resin is 100% UV stable and will not discolour under any circumstances, exposure or timeframe. Clear polyurethanes are more complicated to work with than epoxies and so generally we regard it as a 'professional' material only. Reasons for this include the fact that ideally it needs degassing in order to be bubble-free, there are many more materials that the resin is incompatible with (both moulds and inclusions) and you need to be more careful with your PPE when handling the uncured product. However, if you master working with it then the results can be incredible.

The last thing you mentioned was improving the glossiness of your finished pieces. For this, if you're working with either epoxy of polyurethane casting resins then I would suggest getting a polishing wheel (should be able to pick something up either quite cheaply or more likely a good second hand one) and then using a polishing compound like the Pai Cristal NW1 which is designed for composite materials, especially hard resins like epoxy.

I hope this helps but I would be very happy to answer any other questions you may have.

Have a great New Year.

Matt Statham
Easy Composites / Carbon Mods - Technical Sales