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Em6000
Epoxy pore fill
Wash coat over pore fill to match any sand through a
Looks good w naphtha bath

Had the issue nice and thought it was sanding through pore fill soooo
REMOVED everything to wood and did it all again

Looks good until EM6000 hits it then… bam grey spots.

What is going on?

To the best of my ability there are no sand through me on the epoxy …. And no contamination on the wood

Hen I spray scrap … w no epoxy it doesn’t do it at all so it’s not hitting bare wood and darkening it

SMH. Super frustrated… need this one done
What is going on?




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Are these the areas that just haven’t color balanced yet? After being maybe the most fresh you sanded / cut?
Why does it only show w the finish on it….


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I would use a wash coat of shellac on the Epoxy. If it does not show then it will not show when you spray the EM6000.

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So this has to come off again? Geez
Thankfully it’s a first coat


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Did you dye the bare wood as a first step? If so, your sand throughs probably created the discoloration which may require a fairly deep sanding to even out.

No sir. It’s just wood. No dye


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I did use CA for bindings… BUT it was sealed w shellac around edges .
And i didn’t use it OR shellac on headstock and it’s the same


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Hmm, a real head scratcher. Are these grey spots in the same locations as they were the first time?

Edit to add:

Looking at the picture again it looks like there are some spots where the grey stops just sort of the binding in a line that kind of follows the shape of the edge. Almost like those edges got a little more scrapping in those spots during your finish prep. It makes me wonder if the grey areas are places where the epoxy has soaked in deeper and reflecting light differently. Since you sanded back all of the epoxy, it could be that these areas did not get sanded enough to remove the deeper areas of penetration.

Can you take a piece of scrap and fill part with epoxy and sand it back to but leave some areas with epoxy and do another area where you just apply a thinned coat of epoxy like you did the first time to even out the color. Then spray that and see what the different sections look like?

I guess the question would still be why is it soaking in more in some spots. Did you wet sand before epoxy? Did you clean the surface with anything that may have resisted or drawn in epoxy? Maybe that was not fully flashed off in all places?

I'm just spitballing here.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I’m trying to find a pic …. I know on the headstock they are in different places


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I could call it Leopard Purple Heart if it didn’t look so crappy ha


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I added more questions to my other post in an edit. You may not have seen the update. . .

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

That purple heart looks awesome though! I hope you get it sorted out. Wish I could help. My only guess is it's contaminated or sanded through. I always sand pore filler back to wood to try and avoid things like this.

So I reached out to a another luthier I’ve know a long while and he says it’s because of the epoxy itself. He said avoid it by amusing a sealer under the epoxy.
I suppose I was naive to using a sanding sealer on the back and sides
Probably something I should have always known


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The color of the blotches may be oxidation of the purpleheart. I'm not sure how that would explain it but if that is true, then the color may correct itself. You could try setting the guitar in direct sunlight for a day or two to see if that effects it.

I've not heard of using sealer under epoxy either. What would you use? I don't think epoxy sticks well to shellac.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Suggested shellac. Perhaps he was thinking I would follow w a pumice fill


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I have found that if I apply thinned zpoxy to bare wood, it soaks in and makes dark splotches.
I rub/wipe a final thin full strength zpxoy as the last layer. It solved my problem.
Don’t know if this is your issue.

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wah
Wah-wah-wah-wah
Wah

Ok so if I can’t pore fill over the wash coat I’m just finishing it with fly on fly off and shellac. I’m not sanding this down again, too much risk hitting bindings (some are already thin) and all sorts of stuff


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I did thin it!


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Hey SnowMan, Boy, that's some serious PPURPLE COLOR there. I've been sawing fret boards out of a purpleheart board and even taped on a "dummy" veneer to see what it would look like (didn't use it). My point being is that PPurple on yours almost looks like it was dyed and that the splotches are probably nearer the real color. Maybe there is some that is that PPURPLE AND I just haven't seen any yet.

No sir. The wood was from Aaron Hix. Not dyed. That’s just the color . Good board


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I don't believe that the issue is because of the epoxy, but rather that you've sanded through the epoxy in the spot areas.

Either sand back to get rid of all of the epoxy other than what is in the filled pores or use a wash coat and meticulous squeegee work to leave a thin, uniform coat of epoxy on the surface and degloss/tooth with maroon 3M ScotchBrite. Much like over-sanding of pastewood filler, cutting through to raw wood will usually show up as a difference in chatoyance, color density from dye or stain, etc., especially when a waterbased finish is used. On some flame maple test coupons I did for one project, even plain shellac - if not fresh - carried enough water into the wood to cause some temporary discoloration on inconsistently sanded epoxy pore fill.

Both vinyl sealer and shellac can be used as a tie coat on top of epoxy - just make sure you degloss and ALWAYS use a non-blushing/non-blooming epoxy (i.e., NOT Z-Poxy or West 105/205 or 105/206).

One other idea: High iron content in water used to thin WB finishes can react with high tannin-content woods to show a grey/black iron stain . I doubt this is your issue, as the usual practice is to use distilled water for thinning, so less chance of a tannin/iron reaction.

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Just a thought: Sometimes, it is impossible to pin down the one thing that actually caused a problem. So, you just have to go back and tighten up all processes, and hopefully eliminate it that way. If you used Zpoxy, use Silver Tip this time. Sand back to wood all over. Don’t thin a coat of epoxy (not needed if you are sanding it all back). Make sure to use distilled water as the thinner for the finish. And so on. I had an issue a long time ago with my hide glue joints. I never really understood what one thing led to the failures, but by tightening up all my processes, I have not had any more failures. Hope you can get this to work out. It’s a beautiful back & side set!

I think Dan is saying to not thin the final coat (full strength but not applied thick). I agree with Dan that this may be the problem. You have uneven sealing performance because the viscosity of epoxy on the final coat (to cover the sand throughs) was different from the pore fill coat.

Well yes. I think the exclamation mark was misleading:)
I meant YES! I did thin it. Maybe that’s the issue:)


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