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Let’s Go Over this Again, Epoxy Pore Fill
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13163		 Page 1 of 2
Author:  Bruce Dickey [ Sat Aug 11, 2007 3:30 am ]
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I was somewhat pleased with my second try at epoxy fill. I used a 30 minute epoxy from a local crafts store. It worked pretty well, and did sand well too. My problem was I wiped it down to get rid of the tiny ridges left by the single edge razor blade. I think doing the paper towel and Denatured Alcohol wipe actually had a negative effect, wiping the uncured epoxy out of the largest pores. I more or less only did one pore fill over the entire indian rosewood guitar. I'm up to nine coats of lacquer and still have some tiny pores to fill up, but have not yet sanded it back the second time.

So, if you would, share your methods and materials of this critical step in finishing. TIA.
Author:  JohnAbercrombie [ Sat Aug 11, 2007 4:32 am ]
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Bruce-
I think you've analyzed the problem already, but...
I use the 'standard technique' which has been explained here on the OLF in the past, and it works well.
ZPoxy or WEST (which I use) spread with a plastic autobody 'squeegee'. All excess removed with squeegee, with a bit of paper towel to remove epoxy from binding corners, etc where the squeegee won't reach.
Let cure.
Sand lightly (220) to remove any ridges, etc.
Blow clean and examine carefully. Repeat steps above if unfilled pores are visible.
To even out color if some areas of bare wood are showing, wipe with a diluted solution of epoxy in alcohol. Let cure.
Scuff sand with 320 to get rid of dust, etc.
Put on the finish.

Cheers

John
Author:  SteveCourtright [ Sat Aug 11, 2007 5:55 am ]
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I don't know about West Systems but the Z-Poxy is called a finishing resin, which may be a little different than some other epoxy formulations. Z-Poxy seems to set up pretty fast, less than 30 minutes and so I wonder if, as you say, yours was not fully cured.

Some epoxy is much more sensitive to ratios as well. If you had too much resin and not enough hardener, some of the formulation set up fine, but there was not enough of the catalyst or whatever to turn all of the resin into hardened material. That could be the problem.

I understand that Z-Poxy is less stoichiometrically sensitive than many other formulations, and that is why I use it. Good luck!
Author:  SteveCourtright [ Sat Aug 11, 2007 5:56 am ]
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BTW, my technique is the same as John's (at least theoretically).
Author:  KenH [ Sat Aug 11, 2007 6:05 am ]
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I had a friend who used the 5 minute epoxy to pore fill a black walnut guitar and he had the same kind of problems that you had. This was the stuff that came in a double syringe. He had many problems with some of it not hardening and then sanding it back down was tough also.


I have had excellent results using the Zpoxy finishing resin and squeege method as mentioned above. I do it in 3 coats. The first two are full strength with light sanding between the coats and the last coat is mixed 50/50 with DA. By the time I am finished with the z-poxy, the guitar has a very durable and shiny finish and it makes further finishing the guitar a breeze.


 
Author:  Bill Greene [ Sat Aug 11, 2007 8:57 am ]
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Bruce:

I used West Systems, and did almost exactly what JohnAbercrombie said with the following exceptions: I, too, used a razor blade (with the sharp edges knocked off with the belt sander) to push the epoxy into the guitar pores, BUT, I did this AFTER heating the epoxy gently with a heat gun. When you do this with a heat gun (or lamp), the epoxy will "ever so slightly" begin to bubble (it has a low boiling point) and will seep/wipe much better into the pores - or so I believe.

But like you, I also used plain paper towels to wipe the slurry off.

Author:  JohnAbercrombie [ Sat Aug 11, 2007 9:54 am ]
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Bill's advice on warming is excellent.
The heating helps to get the 'air bubbles' out of the wood, and out of the pores, so that the epoxy can fill the voids.
The general advice is to get the workpiece warm before applying epoxy, then let it cool after the epoxy is applied. That way, the contracting gases tend to 'draw' the epoxy into the wood. I usually don't bother with this on guitars, BTW.
However, if you ever do the opposite- ie cold workpiece, apply epoxy, then warm- you will be treated to a sea of bubbles and pinholes. Off topic: this can really be a problem with epoxy on softwood strips when building canoes and kayaks.

Cheers

John
Author:  Bill Greene [ Sat Aug 11, 2007 11:14 am ]
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Hesh:

You can't mess this one up or I would have, trust me. ;-) The epoxy (well, the West Systems anyway) bubbles visibly, it's not subtle. You'll see it when it does. And it's not very warm AT ALL...a regular heat lamp, waved slowly approx. 8" away makes it bubble within a few seconds. A heat gun, waved similarly, in about the same amount of time. The epoxy is only warm to the touch. There is no exact temperature. You'll see it.

And it easily stays warm and thin for enough time to wipe it into the pores.   I'm convinced it helps, but even if it doesn't, it requires very little time, and doesn't appear to have any negative effects at all.

My .02.
Author:  Jim Watts [ Sat Aug 11, 2007 11:18 am ]
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Bruce, try a rubber squeegee (sp?) to clean the excess epoxy off next time. I think Todd Stock suggested that one. I tried it and it works pretty good. BTW you can always drop fill a few pores prior to final sanding.
Author:  Dennis Leahy [ Sat Aug 11, 2007 1:06 pm ]
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[QUOTE=JohnAbercrombie] Bill's advice on warming is excellent.
The heating helps to get the 'air bubbles' out of the wood, and out of the pores, so that the epoxy can fill the voids.
The general advice is to get the workpiece warm before applying epoxy, then let it cool after the epoxy is applied. ...Cheers

John
[/QUOTE]
This is exactly what Grant Goltz told me (warm the body, apply the epoxy, allow the temp to drop.) Grant has used literally gallons of epoxy on his stunningly beautiful wood kayaks.

I put a lit light bulb inside the box for a few (15?) minutes to warm the body, before applying the epoxy.

Hesh, how the heck do you do that with a credit card? I tried it, and found it easy on big areas and hard on small areas, plus I always seemed to have a ridge to knock down. I'm going with the small (auto body) squeegee next time!

Dennis
Author:  redennis3 [ Sat Aug 11, 2007 4:34 pm ]
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I think I have a few credit cards I could use


                                      Red
Author:  David R White [ Sat Aug 11, 2007 11:56 pm ]
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For the record the West System products are adhesive epoxies, not finishing resins. However, lots of us use them with success. I cut mine with about 5% acetone which I think helps.
Author:  JohnAbercrombie [ Sun Aug 12, 2007 2:59 am ]
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[QUOTE=Hesh1956]
How warm is warm? I mean you don't want to risk weakening a glue joint so what are we talking here as a suggested warming temperature? [/QUOTE]
Hesh-
I was talking about 'warm room temp' or perhaps the heat from a few work lights- perhaps 100 def F at most. The 'cool' part would be a cool room temp- say 60-70 deg F.
As suggested, a heat gun or hair dryer 'waved in the general direction' would do the trick as well, but nothing very extreme is needed (or wanted).
The temptation is often to do the opposite to 'help the epoxy cure faster' by putting it into a warmer environment, and this can cause problems. The epoxy cure reaction is 'self-warming' (aka exothermic) by itself-that's why you'll end up with a smoking lump if you let it cure in the mixing container.

Cheers
John
Author:  Arnt Rian [ Sun Aug 12, 2007 3:32 am ]
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I am one of those who like to leave the filler only in the pores because 1)I want to make sure I have as little as possible of it on the instrument and 2)to avoid the having to touch up the colors if I sand through to the wood later as the z-poxy is slighly amber. I suppose if you never sand through but you still manage to get your finish really thin and beautiful this is not an issue, but I am not there.
Author:  Howard Klepper [ Sun Aug 12, 2007 4:22 am ]
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I use 5 minute Devcon from the hardware store. Not the double syringe--you don't get an even mix from them, especially when using small amounts. Mix a pea-size blob each of resin and hardener. It is very easy to see the amounts accurately. With the 5 minute stuff, you are tack-free in about 15 minutes and can touch and turn the guitar over, and rest the filled surface on your bench. Overnight before sanding. You have just enough time to spread the 2 pea sized amount before it starts setting up. Stop when you feel it stiffening at all, and mix another blob.

Dulled and corner-rounded single edge razor, used like a squeegee. Spread the stuff out working your way across the panel, so that the excess comes only off the advancing side of the blade. I never wipe the guitar with anything, and sanding the excess is not a problem. But I do wipe the blade frequently with a little rag wet with alcohol.

I find that it helps to spray a thin shellac coat before filling, then sand back to wood when leveling the fill.
Author:  burbank [ Sun Aug 12, 2007 7:00 am ]
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[QUOTE=Howard Klepper]
<snip>

I find that it helps to spray a thin shellac coat before filling, then sand back to wood when leveling the fill.[/QUOTE]

Howard,

I'm curious about what you find is gained from the thin shellac coat before filling.

Thanks
Author:  James Ringelspaugh [ Sun Aug 12, 2007 9:43 am ]
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I too am now using the 5 minute devcon epoxy. I used to use the System 3 epoxy that LMI sells, but it takes just about forever to cure. Plus it's just way too thin and extremely unforgiving when it comes to the mix ratio.




Author:  Howard Klepper [ Sun Aug 12, 2007 3:05 pm ]
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The epoxy seems to squeegee better over the shellac. The razor blade glides more smoothly, and you can press on the blade without scraping or burnishing the wood.
Author:  burbank [ Sun Aug 12, 2007 3:47 pm ]
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Thanks, Howard. I would guess that the adhesion problems that some have mentioned with epoxy over shellac might be eliminated with a thin highly diluted shellac mix.
Author:  Ken Franklin [ Sun Aug 12, 2007 6:26 pm ]
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I use the 30 minute Devcon epoxy. I mix half of the epoxy in a small metal cup and thin with acetone until it is runny. Then I brush it on the sides across the grain. It really flows into the pores when it is thin and the acetone evaporates quickly. I mix up the rest of the epoxy and do the same with the back. If it starts to get thick before I'm done I just add a little more acetone. Then I clean my brush in acetone. It's good to have a nice china bristle brush. I sand the next day and repeat.
Author:  Michael Dale Payne [ Mon Aug 13, 2007 12:29 am ]
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I use Zpoxy and credit cards leaving as little on the surface as humanly possible. I do not worry with ridges at this point. I allow each coat to dry 24 hours and lightly sand the ridges off and fill again. Once I am happy with the fill and it has cured out, I sand back to bare wood everywhere. Leaving the Zpoxy fill only in the pores. I then wipe with a 60%/40% cut of zpoxy on to color the bare wood. This is very thin. almost non-existent film as the wood will soak most of it up and it flashes quick so work quick.

Bruce Indian Rosewood can have deep and open pores as you well know. 2-3 maybe 4 coats on pores like this maybe required.
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