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I've just sanded down my first layer of epoxy (S3), and there are a couple of things I found myself wondering, which I've always wondered, and just never found the answer. First and foremost (this may just be one of the dumbest questions ever asked here, but I've got to know):

When do you know you've gotten down to the bare wood? I seem to reach the surface fairly quickly using 320 fre-cut, where only the pores remain shiny, yet the sanded wood is still darkened by the epoxy. In select areas where I sanded considerably longer for one reason or another, the wood seems to lighten back to it's original color. Should I be sanding the whole thing to this point? If so, that will require at least three times as much time and effort. I do plan to do a thinned "wash" coat after sanding back the second coat, so I'm wondering if it's really necessary to be so ... thorough.

Secondly, despite obsessively vacuuming the heel area after sanding, there are still some pores with light-colored dust stuck in them. Will these disappear when saturated with the next layer of epoxy? This leads to my third question --

Do I need to wipe down the sanded areas with naptha, mineral spirits, etc before proceeding to the next layer?

Thanks in advance for any nuggets of wisdom.

Ken

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Mountain Song Guitars www.mountainsongguitars.com

I use a tack cloth, followed by a wipe down of naptha then a detailed blow off with compressed air.

Thanks, Michael. I've always wiped down with naptha, but in Dan Erlwine's Guitar Finishing step-by-step book he describes a series of steps for cleaning the guitar surface prior to finishing, which is naptha, then mineral spirits, the a 50/50 mix of ammonia and water.

I'm curious, do you see any problems with wiping down with mineral spirits?

I was hoping more folks would chime in on the other questions I put forth.

K

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Mountain Song Guitars www.mountainsongguitars.com

Hi Ken,

I've never pore filled with epoxy, but I've only ever used naptha for cleaning the guitar before finishing. I would imagine the mineral spirits and H20/ammonia wipes would insure there was no silicone contamination of the wood, but as I never use silicones in my shop area I haven't had any problems with just using naptha for cleaning.

My method is similar to Michael's using a tack cloth and compressed air.

I also use a tack cloth and naptha wipe in between coats and sessions, mineral spirits would be OK too but it takes longer to evaporate than naptha, plus you've got to deal with the smell.

Cal

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Remember, there are no stupid questions, only stupid answers!

Hi Ken.

Regardings sanding to bare wood, I don't care too much for it. I never saw any epoxy 'staining' under the finish even though there was some areas where I knew I didn't get to the bare wood. Also epoxy, if it's thin enough, will act as a sealer in some way, penetrating the wood fibers. Therefore it's normal to see the wood darker than when it's unfinish.

I know some people here often talked about not letting any areas of unsanded epoxy to avoid 'stains' under the finish, but that never happened to me. That said, I finish with polyurethane, not lacquer, so that might be important in the equation.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)