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Per Ken's request, I'm starting this thread about epoxy fillers. I'd like to hear some feedback from anyone who has used systems three epoxy pore filler, thanks!

David L

It's what I use now. SB-112. I think it is a very good filler and "pops" the grain nicely but like other epxoy's is messy to use.

the best results I had was using nitrile gloves. and rubbed it on . then scraped off with a fresh safety razor. It isn't a bad system and it works but I still use pore o paq. There are many products out there and I think if It was out there when I started I may be using.

I understand Doolin no longer uses System Three -- note that if you check the Internet even when used for its intended purpose "boat building and repair" there are many complaints about the stuff never drying.

Further comments from Mike Doolin:

1) The epoxy is very sensitive to mix ratio, and it’s hard to get it
right when measuring by volume in small quantities. The best thing is
to measure by weight with a triple-beam-balance gram scale. The mix
ratio of resin to hardener is 100:44 for SB112, 100:43 for Clear
Coat. Thoroughly mix the epoxy first, then add the thickener.

I use two paper Dixie cups, one inside the other to keep the epoxy
from soaking through to my fingers. I first weigh the empty cups,
which turns out to be 3.5 grams for the particular cups I use. Then I
squirt in 10 grams of epoxy resin, which makes 13.5 grams. Finally I
squirt in 4.4 grams of hardener, bringing the total weight to 17.9
grams (and making the mix ratio 100:44). I mix this really
thoroughly, scraping the bottom and sides and the stirring stick, and
turning the cup around frequently. I spend a good 20-30 seconds
stirring the stuff, making sure there isn’t any unmixed epoxy in the
corners or on the stick. Then I add the thickener and stir it in just
until it’s all wetted.

This makes enough epoxy to cover a whole guitar if you work fast,
with lots left over after scraping it all off. Remember, the idea is
to leave none on the surface, just in the pores. I wipe the corners
with an alcohol wetted rag to make sure there’s no build-up there.2) The epoxy is also somewhat sensitive to temperature. It cures
better at 70 degrees or higher. After application, hang the guitar in
a warm room to cure. It should be hard but very slightly tacky after
6 hours, no longer tacky after 24.

The reason why I tried zpoxy over system three is that it is much more forgiving when it comes to mix ratios. So says LMI...

darren wrote:The reason why I tried zpoxy over system three is that it is much more forgiving when it comes to mix ratios. So says LMI...

That is why I made the choice as well. It is easy to eyeball 50/50. You have to measure by weight small amounst of three to one or 5 to 1. I have been really happy with zpoxy but I have only put it on two guitars. I used pumice and shellac for my first classical guitar.

I use System 3 because it's how I was taught. It comes out very nice if used right. I have a digital scale to get the weights right and use silica as a thickener. Never had a problem having it dry overnight. I put it on just like John H described. The fact that they don't list it as being used on guitars never bothered me because a lot of things I use building a guitar don't list guitars but the thing is, it's messy. So being able to brush on two coats of pore filler and have it dry in a couple hours is appealing to me. I'm going to try it. I may be an old dog but I'm certainly amenable to new tricks.

As an Industrial Engineer by trade I would submit that epoxy is difficult to use as a pore filler -- because pore filling was not the design intent. That said, you have to wonder why the epoxy manufacturers cannot give out or does not have an on top "over" and "under" chemical compatibility chart. As an example here’s a chart that includes Zpoxy (poly finishing resin) – the design intent for this product is for use by modelers to bond fiberglass to balsa wood. Interestingly the only thing that the Zpoxy goes on top of -- is itself?

kencierp wrote:... Interestingly the only thing that the Zpoxy goes on top of -- is itself?

That squares with the limited research that I did. You need to put the zpoxy on the wood. It did well on the under!

I know this thread is about system three, but I used zpoxy on my last build and found it extremely easy to use--filled quickly, dried thoroughly, didn't shrink, and no adhesion issues with my water based lacquer.

Ken