Official Luthiers Forum!

Having never used an epoxy for grain fill this I am not sure if have the right product. Going through a box, I found some Z-poxy finish resin. Is that what is used and do I need anything else than what are in the 2 bottles? Have some wood laying around so I thought I would try it out before putting it on a guitar. If not the right stuff well then back into a box.

That is the stuff for grain filling. About half of those who grain fill with Epoxy use Z-poxy. I have used and like it. The mixing ratio is not as critical as some epoxies, it sands very nicely, too. I don't have any idea about shelf like of the stuff, so maybe try on scrap first if you have had it a long time. Finally, thinning 50% with alcohol and applying with a paper towel or the like is sometimes used as a last coat, some sand back to wood and thus don't do this step.

Stan my friend in addition to Steve's excellent advice here is how I use Z-Poxy finishing resin.

I use a credit card type card as a squeegee and apply the first coat really trying to mash the epoxy into the pores. I squeegee in all directions working on only say a 6" X 6" space at a time. My final passes are at 45 degrees to the grain and I try to remove as much of the excess epoxy on the surface as possible. I dump the excess on the next area to be done for reuse.

What seems to be the trick here is when applying the epoxy use your squeegee as more of a tool to press the epoxy into the pores and not as a surface skimming, material removal device. Only on the final passes use the squeegee to remove the excess.

Expect to let it cure and sand back and repeat this process a second time. It usually takes me two full coats on porous woods.

Now you have a choice of sanding back completely to the the bare wood or leaving a thin film of epoxy on the wood because it really pops the figure as much as anything I have tried. Of course it is not used on the top unless you want to use the 50% mix wiped on coat that Steve described to add a slight amberness to the top. You can also use it on the top if you are using woods like Koa for the top.

It works very well and once I got the hang of understanding that I need to mash it into the pores and squeegee in all directions my results improved greatly.

Good luck. And BTW one of the fun things about using an epoxy pore filler is that it gives you your first glimpse of what the guitar will look very much like under finish - very pretty.

Stan, I switched from traditional grain fillers to epoxy. I had a couple of instruments with smooth, level surfaces develop depressions where the filler had shrunk. This was months after the instrument was buffed out. I haven't had that problem with epoxy.

I use West Systems epoxy and am very happy with it. It dries hard and light and powders nicely when you sand it. It's expensive but I think it's worth the money. I've used Z-Poxy in the past when I built RC airplanes and found it to work very well. I used it in much the same way, filling the weave in fiberglass cloth.

The only thing I can add to the great advice given by others is to make sure you have a consistent surface before you start your final finishing. Don't leave patches of epoxy on the surface or you will end up with light and dark blotches under your finish. Either sand back to wood leaving epoxy ONLY in the pores, OR leave a thin layer of epoxy as the final coat as Steve Courtright suggested. Both ways work but I prefer to fill in the pores and use a very thin final epoxy coat applied with a paper towel or rag to even out the color/lightness/darkness.

I use this method on my Koa ukuleles and like Hesh said, it really makes the grain stand out.

My first post.....hope I was of some help.
Steve

Anybody tried sealing first? What about filling over a stained mahogany? When you sand back it could ruin the stain if not careful. How do you guys deal with that?

thanks
SR

_________________
"We might not be big but we sure are slow"

SR since Michael Payne is winging his way to China I'll do his standard warning - if using epoxy finishing resin (System III, Z-Poxy finishing resin) or West Systems epoxy do not seal with shellac prior to pore filling. Epoxy will not adhere well to shellac but shellac will stick to epoxy.

So pore fill first and then seal with shellac if sanding back the epoxy to just leave it in the pores. With nitro, a thin film of epoxy on the guitar (mixed 50/50 with DA and wiped on) and not just in the pores eliminates the need to have a separate shellac seal coat.

As Todd said surface prep is very important so if you are going to stain stain prior to pore filling if using epoxy. I would use a very slightly damp cloth several times where ever there is end grain like the neck heel, to raise the grain and then sand back to level prior to staining. This raising and releveling of the end grain makes the stain look more uniform.

If you mix your stain to a custom shade be sure to save some extra stain. It is likely that you may sand through at some point and want to touch it up.

If you are using filler with stain in it then you are not using epoxy to pore fill anyway. I was never able to get the pore filler with stain in it to work for me and found epoxy a real improvement.

I'm a little confused. I keep hearing this on these boards, but instructions for using epoxy as a filler with french polish usually say "apply a sealer coat - then pore fill with epoxy - then sand - then apply more shellac."

In the faq here:
http://www.milburnguitars.com/fpbannerframes.html

they talk about using 5-minute epoxy as a filler and even say it's the best option for a french polish.

"Five-minute epoxy: The epoxy is mixed and then spread onto a small area of the guitar at a time. A razor blade or spreading tool that is perfectly straight with "safe " corners is used to spread the glue. Safe corners means that the sharp corners of the blade has bee removed to eliminate the possibility of scratching the surface of the guitar. Timing is important at this stage. The goal is to mix and spread just the right amount of glue with a minimum left to remove and to get the glue into the grain before the epoxy begins to harden. Correctly done, a very small amount ((about 1/4of a teaspoon) Will be enough to complete ½ of the back plate of the guitar. We let the first application of glue harden for about two hours and repeat the process. After the grain has been filled, we sand the entire guitar with 400 grit wet and dry sand paper until the excess glue has been removed.. We use olive oil as a lubricant for the sand paper. If no lubricant is use the sand paper will load and be useless almost immediately. We found that this is the best alternative to pumicing. As a matter of fact, we are now using this method of grain filling almost exclusively."

Can anyone clarify?

Thanks.

Some epoxies have adhering problems if applied over shellac. Best not to temp failure. Shellac, however, sticks to epoxy just fine in the reverse. As a matter of fact, it sticks fine to most things.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Right - this comes up often here.

Epoxy does not stick well to shellac but shellac (french polish) sticks great to epoxy. I have experienced this personally and so has Michael who is not here to chime in.

There is one way for you to find out though - try it both ways.

Also - Note that I am only speaking of three types of epoxy here and two are finishing resins (SIII and Z-Poxy). In all three cases the viscosity is much thinner then your typical Devcon, big box store 5 minute epoxy. This thinner viscosity, which you can add thickener to for very porous woods, IMHO helps the epoxy get in the pores.

I would not think that the 5 minute stuff provides enough working time, at least for pokey me, and I don't like the thicker viscosity.

Lastly - we have had people post here that the epoxy that they used from big box stores was not any good and things came off the guitar after it was built AND finished...... not good....

@mffinla Milburn does mention epoxy as a filler and it works well by itself, but epoxy does not require a seal-coat and I don't see anywhere where Milburn explicitly suggests sealing with shellac before filling with epoxy.

The classic technique, as taught by Milburn, uses pumice to fill after a seal-coat of shellac. The shellac in the seal coat keeps the pumice and wood fibers in the pores and provides a good substrate for the FP sessions.

BTW, I have tried the pumice technique, and while I may have been doing it wrong, it was a Lot of work. Epoxy is much easier, and gives nice results, even for a beginner, like me.

Correct the Milburn speaks of a pit coat of shellac prior to starting pumice filling and solely in regards to pumice filling.

I just spoke with Bob Milburn. They apply a sealer coat of shellac before pore filling with epoxy.

He also said that system-3 epoxy has problems interacting with shellac. Hence, he never uses it. On the other hand, Devcon 5-minute epoxy works very well.

He did describe the process as 'tricky' and said he's still searching for a more ideal pore filler.

I don't know what Stan will do, but I plan to try Bob's method.

Sounds like he has not tried Z-Poxy. Those who have used that seem to like it a lot.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I don't know whether he has. He simply told me which epoxy he thought worked best as a filler (devcon) and which to avoid (system-3).

Well since I have the Z poxy and will spray nitro, I will go the way as noted by several here. Ditto the no sealer first on the french polish will do the epoxy first and then the polish sessions. I have used the pumice thing before and took a bunch of sessions and work, hope this makes it easier or shorter anyway. I haven't done lot of pore fillers as liked some of the look without it, but going to start going that way and really wasn't excited about the paste stuff.