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I'm experimenting with using Z-Poxy finishing resin for pore filling. First time I've tried it. Refinishing a rosewood veneer table top.

First application, measured 1:1 by volume, mixed and applied full strength. Worked out pretty well, cured hard, sanded very easily. Cool. Didn't quite fill all the pores, though.

Second application, again measured carefully 1:1 by volume, mixed, then added some alcohol, about 25%. I liked how it applied more easily thinned that much. However, it didn't cure as hard. Whenever I use epoxy, I pour the excess amount onto a piece of newspaper, so I can observe how it's curing. The puddle from the first application cured very hard. The second puddle remained rubbery enough to poke into it a bit with a wooden stick.

I know, if I didn't get the mix ratio right, that could cause this. But I measured very carefully, using a small measuring cup, so I don't think that was the problem. Have others experienced a difference in the cured hardness of epoxies when thinned with alcohol?

Any other possibilities you can think of for what could have caused this? The room temperature may have been a bit on the cool side (66-68 deg) when I applied it, but I've kept it warmer (about 72 deg) after observing the rubbery cure the next morning. If temperature is the issue, maybe it was too late (i.e. maybe it is essential to have it warm enough during the application and initial hours of curing - ?). My experience with epoxies is limited, so any helpful input would be much appreciated.

Thanks!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd, I've noticed that too. It seems to stay rubbery when thinned with DA, which I don't like. I've been meaning to try Lacquer thinner.

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Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

By adding the alcohol you effectively changed the ratio. I only thin for the wipe down coat not for a fill coat.

I should mention that I have never thinned Zpoxy for any application that left any film thickness. If you add a thinner to any epoxy you are changing the ratio of both the hardener and the base but you are also changing their chemistry make up.

The only place I use a thinned mixture is for the wipe down to even coloring after final level sanding. This is a very very thin, almost no thickness layer and does not get sanded so the relative hardness is ilrelevant but if I was to leave any film thickness, especially if it was to be sanded I would not thin the mixture.

If you are thinking that thinning the mixture will make it flow into the pores easier, well maybe so but remember that that percentage of thinning is going to flash off and leave you with less volume therefore the fill will not likely be a full depth fill after cure. Better to work the epoxy into the proper well at full ratio even if it takes one or more sessions.

Todd buddy I did something related to what you have done but with System III. As you may know SIII comes in two flavors, a thinner version for less porous wood and a thicker version for more porous wood. I would use both only reversing what you have done.

I would use the thin stuff as the first, wetting coat and the thicker stuff as the second, heavy lifter as far as filling the pores goes. The results were always excellent and only two coats were required. I also used a silica thickener in the second coat too.

So my message here is that you may want to do one of two things. Consider not thinning the Z-Poxy at all, I use Z-poxy straight now and always get a complete fill with two coats. Or if you want to thin it thin the initial coat and not the second coat.

I've never used Z-poxy or System III, but this is the first I've heard of thinning with alcohol. When I was working with boats we used to thin West System with acetone for spraying, and never hand any problems. When thinning epoxy it is generally accepted that you will loose some of the strength and hardness, but we never found any real problems. Then again, we used acetone because it is such a fast evaporating solvent and used a very slow hardener. I'm guessing that this combined with thin coats allowed more of the acetone thinner to escape. We tried heating to thin, but even with a slow hardener it still made for too short a pot life by the time we reached a sprayable viscosity. I've never used epoxy for pore filling on guitars though, but I am wondering why there is a need to thin it for this.

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Eschew obfuscation, espouse elucidation.

Thanks Mike, Michael, Hesh, and David, for your quick and very helpful responses. Where would I be without you folks? ...doing a lot more head scratching and a lot more of this - - that's for sure.

Since I've never used this stuff before, I'm approaching it as an experiment, which is why I'm doing it on this old table before I try it on a guitar. The intent to experiment and learn is also part of why I decided to thin it with alcohol somewhat on the second coat. You know, "What would happen if I...?"

Many folks have discussed thinning epoxy with alcohol during the pore filling process. Most, as Michael described, have talked about doing this only for a final wash coat, for the way it wets and adds color to the wood, and/or for evening out the color if some epoxy was left on the surface after pore filling and sanding back. However, in his guitar finishing DVD, Robbie O'Brien discusses thinning Z-Poxy with alcohol for the second or third application while the pores are still being filled. So, his suggestion was also, in part, what prompted me to try that.

My first application of the Z-Poxy (undiluted), went pretty well. However, having never done this before, I was somewhat surprised at how the epoxy did not flow out or self-level on the wood's surface. Working with a plastic spreader from an auto paint store, I found it difficult to complete the application with a smooth and even coat. I ended up, in that first effort, leaving a thicker coat on the surface than I thought ideal, with plenty of ridges and much unevenness. I realized I should have worked harder to squeegie most of it off the surface after working it into the pores. My main point, though, is that I wondered how well it was flowing into the pores, considering how little flow was happening on the surface. By the way, I had the shop heated to about 70 deg for that first application. Maybe it would flow better at warmer temps, but it certainly wasn't unduly cold.

The good news was that, in spite of how thick and ridgey it was, after curing, sanding it back was a breeze. I was worried I'd be sanding for hours to re-level and get back to, or close to, the wood. The sanding went amazingly quickly. So, that was a relief.

The result of that first application was that it filled maybe half the pores. So, based on those observations, I thought I'd try Robbie's suggestion to thin it for the second application. (Michael, your warning that it may shrink back more, defeating the purpose of perhaps flowing into the pores better, is well taken.)

I actually haven't sanded back the second application yet. I'll be going down to the shop to do that in a minute.

I'm glad to know that others' experience has demonstrated that thinning with alcohol does, indeed, cause the epoxy to cure softer. That answers that question and lets me know I didn't just screw something up. Knowing that, though, leads me to think I don't want to ever thin it with alcohol for use on a guitar. The idea of putting a coat of rubbery stuff on a guitar, however thin it may be, is not appealing. My conclusion for the moment, then, is that I'll use it full strength (I'll probably get better at working it into the pores with practice), do two or more applications if necessary, sand it back to the wood (leaving none on the surface to cause any unevenness of color), and then use something else if I want to wet or tint the wood in any particular way before moving on to other finish coats.

Considering the lack of flow, though, I do wonder about the possibility of pore bridging...

If anyone else wants to add your experience or knowledge to this thread, please do. Those of you who use West System, do you find that it tends to flow out/self-level better?

Thanks again.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

it helps the flow out to heat the surface to short of 100 deg before you start as well but mot required by any means

Todd, I have been using z-poxy for quite awhile and my guess is that as
you mentioned your shop was too cold. Z-poxy won't catalyze well below 69
degress F. You need to maintain that temperature throughout the curing process.
In the winter I heat my shop to 72 when I'm using z-poxy. I also warm the freshly
mixed z-poxy in front of an electric heater for ten minutes and then give it another
good stirring. This gives the z-poxy a chance to start catalyzing before I spread it
on the guitar. I don't thin with alcohol, I tried it once and found that the alcohol
evaporates too fast to be of much use though it might be usefull for fixing a small
sandthru.

Thanks, Michael and Paul. I'll be sure to have my shop plenty warm in the future, and may experiment with warming the wood and/or the epoxy before applying.

Could be that the rubbery cure I got was a result of both the added alcohol and the temp being a bit under what it should have been.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

My guess is the rubbery issue is a combo of thinning the mix and applied with thickness and the ambient temp combined.

Thinning epoxy too much will definitely make it 'rubbery'. I use WEST epoxy, and you only need a bit of solvent to drop the viscosity a lot. I haven't found any need to thin WEST epoxy for pore filling.

http://www.westsystem.com/ewmag/14/pdf/ThinningEpoxy.pdf

You want to be careful about putting warmed epoxy on cool wood, as you can have problems with air bubbles. I second the recommendation to warm the workpiece before applying epoxy. It's better to let the temperature drop after application- continued warming will get expanding air bubbles under the epoxy- this is more of a problem with porous woods like mahoganies.

BTW, epoxy will cure eventually at most temperatures above freezing. Even at room temperature, it takes weeks for full cure, though.
Also, adding solvent doesn't alter the ratio of hardener/resin- you still have the right # of molecules in there for the reaction to proceed to completion. The rubbery quality is more a result of solvent 'getting trapped between' the epoxy molecules (or evaporating and leaving voids).

Don't forget to keep the epoxy off your skin as well-solvent makes it even more of an issue.

Cheers
John

John, thanks a lot for your input. Very helpful, and much appreciated.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

John (et al), which West System product are you using? Do you find that you're able to get a good fill (good enough to french polish over) in one application on a very porous wood like rosewood? Was there a learning curve for you in application technique to get the epoxy into the pores? Any tips on that?

After sanding my second application (which was thinned about 25% with alcohol) of Z-poxy back to the wood, I still have a lot of unfilled pores. I'm quitting there on this table top, because the rosewood veneer is very thin, and I can't avoid sanding a very small amount of it off when I sand the epoxy back to the wood. Don't want to go through the veneer and ruin this table. So, I'll do more tests/experiments on something else.

Maybe I'll just get some West System and try that next...

Thanks!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd-
I've used a lot of WEST epoxy for boatbuilding projects, and I'm quite accustomed to its properties, so that's why I use WEST for pore filling as well. I've never used Z-poxy, so I can't compare the two brands.

I should say at the outset that I'm getting less particular about the 'thick, glassy look' lately and I don't get real excited if parts of the guitar look like wood, so my standards are a bit on the 'low' side for finishing.(!)

I haven't used epoxy under FP, as lately I've been putting nitro (over epoxy) on the b+s and FP on the top. The guitars I built at Sergei deJonge's had FP over 'traditional' (silex-type) filler on the EIR bodies, and FP over pumice/shellac on the mahogany necks. Nitro can work to hide some small pores, better than FP, I think. So I can't answer your question about 'one coat of epoxy as prep for FP'. I'd have no problem spot filling small areas of pores with pumice while doing FP, if necessary, if some had been missed with the epoxy. Generally, one coat of epoxy does the trick for me, but it's better to put on two light coats than to end up with globs and ridges.
I use an autobody 'squeegee' for application -this is just a plastic rectangle. I've also used a plastic credit card-type of applicator. Hesh has given excellent 'technique tips' on this part of the process. Make sure the pores are empty (brush and or use air gun). Put on some epoxy (small puddle) and use the squeegee to 'push' the epoxy into the pores, spreading the epoxy as far as you can. I usually work along the grain when filling, and across at a 45º angle when removing excess. It's better to use fresh epoxy as you work rather than trying to use the 'scraped off' epoxy on a different part of the body- fresh epoxy from the mixing container will be clean (no dust) and have fewer air bubbles. That said, you can get away with re-using if necessary.
Obviously, the back is the easiest surface to do, and the neck is the trickiest.
There is definitely a learning curve to this technique- it might pay to do some practicing with boards from your lumber stash- any porous wood will be good for practicing, and epoxy in these quantities is not very expensive. Your idea of practicing on non-guitar projects is excellent, though veneer is tricky, as you say.

After saying all this, if you are doing FP anyway, shellac and pumice works well and is traditional. It's easy to take your time and re-do small areas, etc with pumice, so it might be more relaxed, if not so 'efficient'. BTW, Sergei adds some dry artist's color to the pumice to darken it.

Hope this helps. Every project is still a 'new adventure' for me- I'm no expert.

Cheers
John

You can use shellac over any pore fill epoxy be it West System, System 3 or Zpoxy. The problem comes in when attempting to put epoxy over shellac as epoxy will not always adhere to shellac. Some have claimed to have used epoxy over shellac but I have done testing and almost always fails when epoxy was applied over shellac and no failures with shellac over epoxy.

I forgot to mention that I usually use WEST 105 resin/205 hardener

If your shop is very warm, you may want to use the 206 (Slow) hardener, though once you get the mixed epoxy spread out on the workpiece, the reaction slows down a lot, since the heat generated is easily dissipated. If you leave mixed epoxy in the pot, it can get smokin' hot.

Cheers
John

Michael, I appreciate your repeated warnings about putting epoxy on top of shellac. Thanks to you, I won't make that mistake.

John, thanks again for all your helpful input. I'll have to search the archives again and try to find the tips from Hesh and/or others on filling the pores with epoxy.

I vacuumed the surface thoroughly before beginning the pore filling, but maybe blowing with compressed air would have given me better results.

Beyond that, I guess I'll just have to keep practicing on scrap to get the technique down. My goal is a very thin FP finish that's glass smooth, accomplished in a short time span (a la the Brune method), so I'm looking for 100% fill from the epoxy. I figure, if I can achieve that and get good at it, it will be considerably more efficient than using pumice, and make a FP finish more viable in terms of the time involved.

One again, thanks!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I mentioned it again only because you were inquiring for an epoxy suitable for French polish and I was not sure you were referencing appearance under the finish or adhesion of the FP shellac to the epoxy or both and we have many lurkers that might not have know the issue or may have it backward as has been the case in the past.

If you first take a few days and practice you should be able to FP the body and have it ready to play or final assemble in a mater of a week with 3 days to cure counted in there. Keep in mind that 10 days to cure out might be better depending on temp and such. but other than the elbow grease it takes to apply the French polished finish It is by nature a short turn around finish

Let me give you a couple good tips here before you begin.
1. A day before you start practising and again before you start the actual guitar, make up your muneca and do the inner pad load up as explained in the Milburn tutorial. Then place the muneca in an air tight container this allows the inner pad's shellac to setup a bit but not totally harden. This will make acquiring the proper flow out of the residual shellac happen properly. If the inner pad is too wet then even with the recommended boding load up as explained in the Milburn tutorial or anyone else for that mater, the flow out will be too wet and will cause you issues. Always store your muneca in this air tight container between sessions.

2. Also have lots of outer covers cut and ready to go and don't be reluctant to change outer pad before you notice any dirt build up or wear of the pad. This is very important if you decide to use tee shirt material as they will collect more dust and store it in the multi dimentional weave as well as wear and start losing fibers into the shellac much quicker than well worn muslin.

Good luck and holler if you ned help.

Thanks for the info and tips, Michael! Much appreciated!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd, I use the West System 207 which the manufacturer says is the clearest, and have always needed two or three coats to get the pores fully filled.

I would suggest your problem is you are using too much thinner. I have always used acetone and found that a very small amount will greatly increase the viscosity. I haven't measured to give you an actual percentage but I just put a few drops into 60mls of epoxy - I would guess 5 or 10% max by volume. It always dries hard.

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David White, Toronto

"All my favourite singers can't sing."

Thanks, David!

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

First time post; I am in the process of using Zpoxy for the first time, and have studied the archives, I can't remember what sandpaper grit you all are using after first application?

Thanks, Chuck

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I'm always the guy who has problems doing things the way it works for most folks, and pore filling has been no exception, driving me nuts. I started using zpoxy, trying to follow advice from everyone who listed info on this forum about it. Good advice too. I like sanding back to the wood, leaving it in just the pores, and I either always have a "bridging" problem, or problem opening up new pores when sanding as carefully as I can . Hesh has said that you have to mash the crap out of it into the pores, and that helps, but, I just still have had problems getting a good fill on 2 or more applications. My current build is a high flame Koa, and I have tried something slightly different. I mixed up zpoxy, spread it on, mashed the crap out of it with a rubber squeegee. I then removed as much as I could with the squeegee, leaving some of the tell-tale ridges, areas wetter than others, etc. and hung it up for a while. While the poxy was still tacky, yet dry enough to handle, I laid on a second coat full strength, heshed the crap out of it again. Then I took a hair dryer and slightly heated the poxy on the surface of the guitar . The stuff thinned out wonderfully. I did see a few bubbles appear, probably from the open pores. I let it cool a little, hoping the cooling would contract any air in the pores and draw in the epoxy. Then, I squeegied again, moving the epoxy around and wetting some of the drier areas. I did not squeegie it off. I let it dry for a day. Then, I took a scraper and knocked down the high spots, sanded with 120 until I JUST started to break through in areas. I swapped to 220 (fre-cut gold open coat) and finished sanding out the areas with epoxy until everything was back to the wood. I sealed with a few coats of vinyl sealer, then leveled the sealer with 320, then 400 until all the remaining pocks of the residual pores were gone. Shot a coat of nitro, and it is the smoothest one yet. I know this is kind of aberrant from the way it works for most folks, but this has been the only way I could get it to work for me. I always have to be the one that the weird stuff happens to

sorry bout the long post, but it's been a while since I chimed in anyway...been workin' on guitars!!!! I hope you guys have all been doing well.

Brad Tucker

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Brad Tucker

Hey, Brad. Thanks for sharing your experience. Very interesting.

(I've been away, or I would have responded sooner.)

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/