Epoxy as clear coat finish over stain?

[RocknRolf]

Hi everyone,

I started planning some details for my DSCM 1q kit (expected to arrive in March) and currently looking into a High-gloss, durable clear finish.

I am planning to use the Crimson stains again on the quilted veneer, but unlike using acrylic clear like last time, I am looking for a more durable finish, as my TLA scratches easily.

1. I know many of you use True-oil, but I read this will cause yellowing, affecting the planned colour?
2. Then a lot seem to use the Cabbots wipe-on or sprayed poly from bunnings. I consider this an option as I think it will be harder than the Acrylic clear, but what is your experience with yellowing?

3. Then there is epoxy: I use the product a lot, and though the formula is tweaked for surfboards, I think it might be great for finishing a guitar, or will it not?
It is hard, polishes up nicely (as long as you can keep the bugs out ), doesn't require you to wait for over a month to start polishing and I have heaps of it.


Has anyone used epoxy as a finish on a guitar and what have been your experiences?


Thanks in advance!

[Simon Barden]

You want a thin finish on the guitar that’s got a certain amount of flex in it. Too thick and hard, and you end up with guitars with no body resonance that sound dull and flat, like the thick polyester finishes on a lot of guitars of the late 70s to early 80s.

Read any article on luthiers’ opinions on a good finish and they will all say a thin one, generally regardless of the finish used.

So can you get a very thin epoxy finish? Being harder than other finishes, I’d imagine it would ideally need to be thinner than them as well. You can probably easily apply a 1mm thick layer of it, but what about a 0.1mm thick layer? I’m not at all familiar with using epoxy like this, but I’m sure you have a good idea of how easy or hard it would be to achieve.

[Rabbit]

I don't know what epoxy you are using, but with timber you need to have UV protection. I think just about all epoxies for timber boat building say to overcoat with clear. The Australian Bote Cote epoxy I use has amongst it's range of hardeners a non-yellowing hardener which has UV protection but they still recommend a top coat. They make a 2k water based poly urethane that you use a cross linker rather than the nasty iso cyonate hardeners used in auto urethane . My canoe has had no issues with it. If I didn't have neighbours living cheek to jowl with me I would prefer automotive clear... modern formulations are hard without being brittle and I have the filters for breathable air for my air fed mask. A half mask wont cut it, since the nasties can be absorbed through your eyes.

[RocknRolf]

Thanks for your input,
Really valuable comment regarding the thickness, flex, uv-resistance.

@Simon: Epoxy has more flex than poly, so let's assume that's ok. Regarding the thickness of coats, I can do a batch 'eau bain marie' (warming it in a container in warm water), this will increase the viscosity a lot, which in turn allows for a thinner coat.
All in all after sanding I think the coat will be in the order of 0.1-0.5mm.

What I think will be the most tricky part and perhaps why I will consider going with the poly products is: when you start having fish eyes due to any contamination and you need to sand it back, because it is so hard, it becomes easy to sand through your finish if you know what i mean. And particularly with a carved top like the DSCM this got me slightly worried.


@Rabbit: Thanks for the comments on UV resistance and safety: I added a link to the datasheet if you're interested. All surfboard epoxy's have good flex properties, are more viscose than boat epoxies and have UV protective properties added to them. That being said, they still do yellow over time, but I think not nearly as bad as what I've seen from the tru-oil results. Even one of my 8-year-old boards is mildly yellowish white.
https://www.fibreglass-resin-sales.c...-Surfboard.pdf

I think Simon has a fair point regarding the thickness of application and with that in mind, you cannot beat a spray product. From what I've seen of wipe on poly, it will match epoxy in thickness.

[McCreed]

I have no experience with epoxy other using to stick things together, and certainly not as a coating, so can't weigh in on that topic.

However, I will say that if you think you will carry on with this guitar building caper, it could be worth investing in some spray equipment.
You can even get by with an inexpensive airbrush for guitar work. It opens up the possibilities of finish materials, whether you want lacquers or poly, and you're no longer restricted to colour choices on the shelf.

Since you do surfboard building, you may already have a compressor. If so, you're half way there.
I've been spraying my poly exclusively the past few years and it makes a huge difference in the quality of the finish because you can apply a more consistent, controlled layer than wiping on or even a rattle can. IME, the coats can be applied a bit wetter (thus thicker) so you get a quicker build of finish. Even with my cheap eBay airbrush I get better results than I even got with wipe-on or spray can. I mostly use my touch-up size gun now (.08mm nozzle) but the airbrush is still handy.

When it cools off in the Autumn, I plan to spray two previous builds that have hand-applied poly finishes on them.

[Rabbit]

Regarding the thickness of coats, I can do a batch 'eau bain marie' (warming it in a container in warm water), this will increase the viscosity a lot, which in turn allows for a thinner coat.

Erm, I think you mean make it *less* viscous. The lower the viscosity, the thinner it is. Epoxy can be applied pretty thin. It's a plastic that can ce sanded thin if needed and then buffed up. As a top coat I still think I prefer spraying Urethane, but the epoxy makes a great grain filler! (provided you don't sand through it!)

[RocknRolf]

hahaha, Google, definition: Damn, Less viscous, LESS

Thanks for your two cents, good to hear someone who knows both 'products'.

As for urethane: Do you also use the Cabots spray varnish? Link: https://www.bunnings.com.au/cabots-e...B&gclsrc=aw.ds

[RocknRolf]

I have no experience with epoxy other using to stick things together, and certainly not as a coating, so can't weigh in on that topic.

However, I will say that if you think you will carry on with this guitar building caper, it could be worth investing in some spray equipment.
You can even get by with an inexpensive airbrush for guitar work. It opens up the possibilities of finish materials, whether you want lacquers or poly, and you're no longer restricted to colour choices on the shelf.

Since you do surfboard building, you may already have a compressor. If so, you're half way there.
I've been spraying my poly exclusively the past few years and it makes a huge difference in the quality of the finish because you can apply a more consistent, controlled layer than wiping on or even a rattle can. IME, the coats can be applied a bit wetter (thus thicker) so you get a quicker build of finish. Even with my cheap eBay airbrush I get better results than I even got with wipe-on or spray can. I mostly use my touch-up size gun now (.08mm nozzle) but the airbrush is still handy.

When it cools off in the Autumn, I plan to spray two previous builds that have hand-applied poly finishes on them.

I'd love a compressor and airbrush, if only I had a shed... At this moment I have nowhere to put all the ideal gear, unfortunately, so have to stay with the strictly necessary gear for now. The airbrush would be a great addition to the finishing options with board building as well so who knows.

But thanks, and yes your finishes are lovely.

[Rabbit]

hahaha, Google, definition: Damn, Less viscous, LESS

Thanks for your two cents, good to hear someone who knows both 'products'.

As for urethane: Do you also use the Cabots spray varnish? Link: https://www.bunnings.com.au/cabots-e...B&gclsrc=aw.ds

Erm, no, I don't use Cabots. I use Aquacote clear https://boatcraft.com.au/Shop/index....dex&cPath=5_38.

[jimmyedson]

I have used epoxy as a finish using Indian ink as a black colour to stain the epoxy. This looks good but I have found it very difficult to get a smooth bubble free finish despite using a heat gun and gas torch to remove bubbles. I also tried epoxy as a clear finish and had the same issues. If you have experience with epoxy you may get better results than me.