MIMF

I'm using West Systems 105/207 for a pore fill and sealer for the first time and having some challenges. The woods are fairly porous, black limba on the back and wenge neck-through with a padauk top, so lots of pores to fill. I'm having trouble with getting a nice even layer of epoxy layed down. First coat I did I scraped back with an old credit card as I've seen in lots of write-ups on pore filling, that left the surface pretty streaky and uneven, and I thought I might like to build up more of a barrier anyway so I emailed the company for advice. They suggested using a cheap, disposable paintbrush with the bristles cut shorter for more stiffness. This was able to push the epoxy around on the surface pretty good but I was picking bristles out of it the whole time, and the result was pretty darn thick and not especially level. When sanding that coat back with 400, I could immediately see lots of hills and valleys as I knocked the gloss off the peaks. And I wound up with a number of drips down the sides - those aren't real fun to level out with this stuff. And of course wound up exposing some wood when sanding back - it's a pretty curvy guitar.

My end goal is to have not only the pores filled, but to have a bit of a barrier layer coating the guitar, over which I plan to put a coat or two of permagloss u40 (as I've seen heartily endorsed here by David King), and bringing that to a satin with steel wool with lube.

So, those of you who have worked with this stuff, any pointers on getting a consistent coating without spending the rest of my life sanding back and re-coating?

Use a single edge razor blade with a burr turned on the edge and the corners knocked off (with sandpaper or a stone) to scrape down the runs. Buy a cheap HF oscillating tool to carefully sand the rest of it. You will find a million other uses for the oscillating tool.

I get a pretty even layer of epoxy using the fake credit cards you get in the mail as a promotion. Push the epoxy back and forth on the surface several times to work it into the pores and a final scrape should leave little build. Curved sections are better done with a gloved finger as a pusher and a squeegee. The epoxy takes several hours to dry so take your time and get it smooth with no build up on the surface. Then you don't need to sand the cured epoxy very much at all. The final layer is best done by thinning it with about 10% alcohol.

The cure for the loose bristles is to buy a better brush.

Cool, I'll give all that a try. Didn't even know there were sanding attachments for those oscillating tools, always glad for an excuse to get another gizmo.

Is it misguided to try to build up a coating of the epoxy on the surface when I'm going to cover it with the permagloss anyway? Would I be better off just trying to get the pores filled and surface level?

My impression of the epoxy pore fill method was to aim for no build up on the surface, just epoxy in the pores. It may be the wrong product to use if you want it as a layer of finish. Unless I had tried and proven a method to level it as a permanent finish, I would probably try to just use it as a pore filler.

Scrape off until you can sand, then level. Epoxy is much better applied with a commercial/industrial grade squeegee...credit cards and other work-arounds do not push the epoxy into the pores are effectively as a squeeze and fail to remove enough excess to avoid excessive build-up on the surface. Etore brand squeegees are excellent. My vids on YouTube cover use, etc.

https://youtu.be/YYHxMg7n9cI


There three schools of though:

1. Apply a lot of epoxy and warm it to level, then tooth for finish (if you don't mind a couple mil of additional finish thickness, go for it)

2. Apply a lot of epoxy, work into pores, squeegee off all excess to get a fraction of a mil surface thickness, then sand back to pores (may open up other pores during sanding, but three coats usually get most filled...more work than 1 or 3).

3. Do as 2., but don't sand back to wood...leave a well-under-1-mil film that is toothed for next coat or sealer (requires careful epoxy removal to achieve a sub-mil final thickness).

I do 3, but it can be a challenge on rosewoods...which may required a final wash coat for even color on amber epoxies like Z-Poxy Finishing Resin.

Thanks Todd, I'd actually already seen your filling video on YouTube but didn't think the squeegee would be that applicable to a curvy solidbody. I'll give that a go, especially as I've not been saving up fake promo credit cards

Todd, on #1 above, you say "warm it to level", you mean with a hot air gun? Does this make the epoxy flow enough to self-level? And does that work across a curve?

I'd suggest a different strategy, namely to use the 105/207 as your final finish. It'll take a minimum of 2 coats and a fair amount of sanding.
West systems will flow out very nicely if you apply it to a previously warmed up guitar but you need to work fast. I mix up the 1 oz single pump minimum in an unwaxed paper cup (pour that into a second cup and mix again with a fresh stirring stick.) If you can degas effectively do that now. Set that cup in a pan with ice to keep the epoxy cool as it will immediately warm up and start to thicken. Pour about 1/2 the epoxy onto the top of the warmed guitar and brush it out with a 1" sable watercolor brush (think $$). Flip the guitar over and repeat with the other half of the chilled epoxy on the back. You need to let the instrument stay flat suspended on the ends in a rotisserie arrangement. You can then concentrate on popping bubbles, removing debris and turning the guitar over at regular intervals to minimize runs. The more curves the guitar has the more smoothly the finish will settle down and lay out.
Let the epoxy harden in a warm room for 8 hours and sand back to level with 320 grit on a stiff foam rubber block. The second coat should lay out even better than the first. Start sanding at 400-500 and finish off with the Si carbide foam pads to get all traces of scratches out. When you're satisfied with the thickness and flatness and all the scratches are gone you can rub in a thin shine of Tru-oil and leave it at that. Clean you brush ASAP in acetone and work any traces of epoxy out of the heel the best you can.
The Permagloss is a very tricky varnish to work with and while the gloss looks fantastic it doesn't look so hot as a satin. It dries extremely quickly so brushing it on a large surface smoothly is nearly impossible. It can be sprayed and can be thinned with acetone by about 5% but that's not ideal. The smell is truly frightful even outdoors. It doesn't sand well and is very resistant to buffing. That said is it probably the whitest, brightest and toughest finish I've ever used. Additional coats don't cross link and you will get witness lines which is what makes it frustrating. As soon as you've opened the bottle it will start to thicken and skin over in a few days to weeks depending on your RH. The shelf life is short, about 6 months unopened. You must clean up the rim of the bottle before putting the cap back on or you may never get it off again. I use it for small items like switch tips and knobs where it can lay out perfectly if you're lucky.

Yes - it self-levels if heat is moderate, and the film thickness and surface tension characteristics generate a relatively even film thickness if carefully applied...but don't take my mention of the approach for endorsement - putting 3-4 mills of epoxy on the guitar in addition to all the material in the pores seems like a good way to build excessive finish thickness. The other issue with the approach is that too much heat will warm the air in the pores and may force it into the nicely leveled-but-still-liquid epoxy.

As David mentioned, warming the article to be epoxy filled or impregnated BEFORE the goop goes on causes the air in the pores to be heated as well as the surface, so after the epoxy is applied and spread, contraction draws epoxy into the pores for deeper penetration. This has been a common strategy for boatbuilders for epoxy encapsulation. Keep in mind that the heat can cause epoxy made up with fast hardeners to kick earlier, so slow hardeners seem like something to consider if trying to warm the work or mixed epoxy before application.

If memory serves, OLF had a series of posts on the topic - I suspect you might still find them retained in their archives.

I have been using epoxy as a filler for a few guitars now. I use squeegees to level the surface. I find I can lean on it a bit more, and get a really thin coat. I find that using Todd's method of moving back and forth in a chevron shape, of simply back and forth on different angles, works well to work the epoxy into the wood.
I have only built electrics also.

I went to my local hardware store and got 3 window squeegees. I cut two of them down to a shorter length (maybe 3 inches) to use on the sides, and in the cutaways.
I found one that had a larger rubber piece; about 3/4 of an inch wide instead of 1/2 or 3/8. I cut it shorter too and removed the rubber and cut the working edge in an arc for working on carved top guitars. The third I left full length to do the final leveling on the flat surfaces. I also use a gloved finger in the tight areas.
So in effect I use two or three different methods depending on the shape of the guitar.
As the guys have already said, use a slow hardening epoxy so you have lots of time to work and catch those pesky runs before they dry.

David, that's a good warning about the permagloss, sounds like that might not be the stuff for me. I've got some tru-oil on hand and had good experiences with that, I really like the satin I've gotten from it in the past.

Questions:

1. the rotisserie rig you describe sounds kind of tricky for this project - it's a neck-through with angled headstock, be kind of a pain to rig at the headstock end. Is this just meant to allow doing both sides at the same time, or do you find it important for getting the sides and curves even?

2. heating the guitar - I've already filled the pores, so is this still desirable? Is the heat to do some of the air-in-the-pores expansion others are describing here, or is it to help with flow and cure of the epoxy? And how warm/hot are we talking? just slightly warm to the touch?

3. Those sable brushes are priced like they're unicorn fur - do they really make a big enough difference to justify the cost? I'm guessing yes since you're suggesting them...

4. "If you can degas effectively do that now." - you mean applying vacuum to the mixed epoxy, or something else? Don't have a vacuum pump, but been thinking about getting one anyway...

5. "unwaxed paper cup" - I've got some assorted plastic cups specifically for epoxy mixing, have you found problems with these?

6. "Si carbide foam pads" - is this "micro-mesh" like LMI sells or something else? And how fine do you go with this typically?

7. popping bubbles - just with a needle or something? any need to draw them out with heat?

Thanks for the info, wish I'd asked all this before I started covering the guitar in epoxy!

There's no need to heat or otherwise fidget with the epoxy filler if you just apply enough on the first coat to fully wet things out and then remove as much as you possibly can with the squeegee...if the film is thick enough to show bubbles or 'juicy' areas, keep taking it off. Second and third coats take less epoxy, but the idea is to remove as much as possible each time so that prep for the next coat is a light scuff with 320 to knock off the nibs and ScotchBrite maroon to degauss and tooth. Three coats will fill all but something like super curly ash, which might take 4 coats. The advantage to epoxy is that the stuff twists light in a nice way; the disadvantage is that it's not a one coat filler like most of the new latex or UV products, so eats some time.

1. the rotisserie rig you describe sounds kind of tricky for this project - it's a neck-through with angled headstock, be kind of a pain to rig at the headstock end. Is this just meant to allow doing both sides at the same time, or do you find it important for getting the sides and curves even?

David, I use the rotisserie for spraying as well so it's a reasonable investment of time, I have three of them now. With West systems you end up mixing enough epoxy for both sides of a guitar including the neck and headstock so my cheapskate nature resists tossing 1/2 of it out every time. I make an expanding plug that fits into one of the tuner holes and is angled on it's arbor to counter the headstock angle. The arbor lines up perfectly with the center of the neck shaft. The strap button hole at the butt end of the body is it's axial counter point.

2. heating the guitar - I've already filled the pores, so is this still desirable? Is the heat to do some of the air-in-the-pores expansion others are describing here, or is it to help with flow and cure of the epoxy? And how warm/hot are we talking? just slightly warm to the touch?

Both air expansion and flow here. The iced epoxy is noticeably thicker and it immediately starts to flow when it hits the cold guitar, it also gets sucked into the pores as it cools the air inside them.

3. Those sable brushes are priced like they're unicorn fur - do they really make a big enough difference to justify the cost? I'm guessing yes since you're suggesting them...

Ah yes true sable is off the menu so just get the best quality faux red sable you can find on sale at Dick Blick or equivalent. The cheaper faux brushes will stay sticky and clump up when cleaned in acetone.

4. "If you can degas effectively do that now." - you mean applying vacuum to the mixed epoxy, or something else? Don't have a vacuum pump, but been thinking about getting one anyway...

I have two vac pumps and neither comes close to de-gassing epoxy. I suspect it takes a 2 stage affair that's measured in Torr rather than inches of Hg. There are mixing systems that avoid air bubbles and one of those might be the answer, see: http://www.mudhole.com/CRB-Epoxy-Mixing-System-EM1

5. "unwaxed paper cup" - I've got some assorted plastic cups specifically for epoxy mixing, have you found problems with these?

Cheap and with smooth interior walls is all you need. If you can pop out the epoxy clean and reuse them so much the better.

6. "Si carbide foam pads" - is this "micro-mesh" like LMI sells or something else? And how fine do you go with this typically?

I get the 320 grit ones from Klingspor and they break down very quickly to a much finer grit, closer to 2000 after a few weeks. See:
http://www.woodworkingshop.com/product/ ... get=bottom

7. popping bubbles - just with a needle or something? any need to draw them out with heat?

I try to pop them with a needle if I can. I've not had luck with the flame method though there is a spritzer you can buy that's supposed to take care of them. I just don't trust adding anything to the epoxy that would affect the cure.

De-gloss; for some reason, Mac Sierra OS changes 'degloss' to 'degauss' (not unexpected), which I've found I don't have to do too often ...other than on steel-bodied instruments .