Official Luthiers Forum!

Hey All,

I am having an issue with epoxy pore filling. I have been dealing with this issue for 6 guitars now. I keep on getting a blueish haze. It seems that the only way for me to get rid of the haze is to strip the guitar and re-epoxy the area or whole guitar. I have tried various grits of sanding on the epoxy. I have tried wiping the epoxy down before I coat with finish. It seems very random. I will even sometimes get this haze between coats of epoxy. I use 320 grit sandpaper between coats of epoxy and finish. I use west system epoxy. I wipe down with naphtha between coats of epoxy. I did only one guitar with z poxy and I did not have any blue hazing issue. I would like to note that I do pore fill in a low humidity environment, so I dont think amine blush is the issue that I am seeing. Has anyone else experienced this? What did you do to remedy the issue? Should I give up on west and look for another brand? Any help would be hugely appreciated. As I said I have been dealing with this issue for far too long now. Thank you for reading.

If you are using 205 hardener that is your problem. Please don't ask how I know this.

Hate to ask but what issues did you have with the 205?

I have used both the 206 and 205 with the same results. I am currently using the 205, but used the 206 on the earlier guitars.

Amine blush, unlike blush in lacquer, has nothing to do with humidity. It is caused by free amines left in the matrix after curing and is caused by improper mix ratios. I always use a digital scale to mix my epoxies. But that may not be the problem as you have already noted. I do not use West system but in looking over their tech data it looks like the only hardener recommended for applications such as this would be 207. I prefer System 3 epoxies and use their SB112 with fumed silica thickener for my epoxy pore fills.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

+1 to mixing epoxies BY WEIGHT and using an ACCURATE gram scale.

They say to mix that hardener 3:1 resin/hardener .... and that's a volume ratio that won't be the same as a weight ratio. Call the company to get the weight ratio.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I use the west system pumps for the mixing ratios. I imagine those to be relatively accurate enough.

Anywhere that the epoxy was (to quote Robbie O'Brian) a scouch thicker, very much like your photo, I have had blotches. The odd patch that was enough to make you, (a) hit your head with the nearest hard object or (b) refinish the guitar. I have done both but am not sure which option provided me with the better satisfaction.

Save your 205 for glue ups. Buy some 207. Good enough for Joe White and Trevor Gore............. They endorse it over any other product I think. Maybe they will chime in.

I am presently using Z Poxy. I am fairly happy with the results. No blotching. Not too bad to sand. I have been doing the final coat thinned with alcohol. FWIW I've been finishing wood for 30+ years and nothing has thrown more curve balls than instruments. But if it was easy, everyone would be doing it eh.

What is that lovely wood you are finishing Robbie?

Cheers,
Danny

Well, I have yet to see West System do anything like that. As Todd mentioned above, you may see a slight amber color on lighter woods but blue?

It might be possible that you have built up a "puddle" of epoxy in that area but even if you did, it shouldn't appear as a blue hue.

Just for information's sake, I apply the West System in such a way that there is no measurable amount of epoxy on the surface of the wood. If you were to swipe a panel with 400G that I applied with epoxy, you would have wood dust. I use it very sparingly.

Sent from my DROID RAZR using Tapatalk 2

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jw ( o)===:::

Definitely use the 105/207 combination. Make sure it's mixed well etc. etc. I've never had a problem with either thick or thin coatings.

Are you getting cross contamination from something else, e.g. mixing pot, applicator, brush that has been used for other purposes or "cleaned" with something incompatible?

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

All of the materials I use are always fresh. The only thing that I reuse is the mixing cups during the pore filling for one guitar. I just pop the old epoxy out of the container since it doesn't stick and reuse it. I can't imagine the coat thickness to be the issue. I know of some guys who lay up carbon fiber with this stuff and they seem to not have any clarity issues. Also if there are any thickness variances I cant imagine it being very significant. I also give about a minute or so for mix time.

I know I am doing something dumb. Everyone else seems to use this stuff with no issue and I seem to only have issues. Thank you for helping narrowing down the possibilities.

Btw the wood is wenge

Rob, I just think you need to sand that blueish area down more. Most finishes darken wood. Any fillers will resist that darkening. The opposite will happen if you sand through the filler. Dark spots.

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Jason Moe
LaCrosse WI 54601

It took about a year but I have seen it on 2 guitars. One EIR and the other Brazilian. The blotchy areas were spots that the epoxy had an undetectably thicker film until it showed up with age. I have used 205 on other woods without issue. Sapele and Padauk were at least 2 I remember. The plus side is I am getting pretty good at refinishing guitar back and sides and leaving the top untouched. Your choice but why risk it.

Cheers,
Danny

Hmm I guess it is possible that it is due to thickness. Which is kind of odd, I try to go as thin as possible with the epoxy. What do you guys recommend? Strip it? I am sure the pores will probably stay pretty full. I can then just shoot clear from that point. I am not sure if I trust the epoxy enough to try this again..... maybe the next guitars I will. I am still quite certain it has to be me that is making a mistake along the lines somewhere. I may try to do some experimenting on a scrap piece of something sometime, and try to get the bluish haze to appear. I then may be able to narrow down what is going on here.

IMO, you need to weigh West epoxy for best results with a small mix. Unless the pump chambers are fully primed, you won't get an accurate mix. If you use a scale, you can mix very small amounts & waste less glue.
West publishes the weight ratios... 5 - 1 for 205 hardener & 3.7 - 1 for the 207.
Personally, I prefer Z-Poxy for filling. I find it hardens better when thinned & sands much more easily than West.
I haven't had clarity issues with either, but I'm VERY careful with my measuring. Fingers crossed... Knock on wood......

Les (?) If you are applying the epoxy really thin as I do, stripping it would amount to no more than skating across the panel with 320 to remove the film and leave the epoxy in the actual pores/grain. Then you can simply apply another final coat if you want. You didn't mention if you are thinning the West System? I have never done that and frankly have never understood the need. Just wondering aloud I guess, if you are thinning it, it might be worth a try to apply it without thinning.

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jw ( o)===:::

One thing I think worth mentioning about epoxies, They are primarily designed for structural purposes. Marine, aerospace and the like. As such, things like optical clarity are usually not a concern to the engineers who design them. This is where not all systems are created equal.

Robbie, did you try calling west systems tech dept? Curios what they might say.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I have had 105/206 go whitish a long time after the application, as have others. I took this up with WEST and was told it was due to moisture absorption*. 207 "special coatings hardener" or "clear hardener" was put forward as the right product to use. I always understood "clear" to mean non-whitening rather than "water white", because there is always some amber tint, to some degree. I have never had any problems with 207. I don't think film thickness has anything to do with it, as I've had no problems with either thick or thin films. If you sand through, though, it can be quite obvious on some woods. If you don't get a good wet-out, for whatever reason, I would expect that to be problematic, too. If you sand to a really thin film, which is discontinuous on a micro-scale, then hit the surface with a solvent, the damaged film can lift, depending on the solvent, which might be giving you the streaky look in the pic. Surfaces that are less than 24hrs cured seem more susceptible to solvent damage, but I don't know that leaving longer gives you totally immunity.

Another thought: these are not micro-bubbles due to over-working the product on application are they?

* When having this conversation with WEST, discussing moisture absorption, we were talking about the cured product. I think the unmixed 105 product can also absorb moisture if the lid is left off for long enough. I don't know if this causes problems or not, but best avoided, I would think.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Not a problem with the pores being full. If you want to fix this and not have it happen again,IE can't live with it, sand down to bare wood and no more. The last time I was at this step, I bought some Z-Poxy and re coated (Todd Stock toot method, thanks bud). One light coat, sanded and sprayed finish. Golden.

Ain't finishing a biach!