Grain fill woes

Neverwhere

Member
Messages
608
Anyone have some grain filler that works without much hassle?
Prepping bodies/necks for paint has proven to be the most difficult/irritating part of building guitars (for me).

I have tried these products quite a bit with meh results:

Stewmac/timbermate
This stuff needs to be thinned down by a lot, maybe 60% water to have thin enough viscosity to work it's way into small mahogany pores/grain. Seems to have decent body when it dries, but requires multiple applications, when you reapply more, the stuff in the pores re-activates and lifts up out of the pore. Finding it really difficult to have it stay in there. Sands nice. Application of initial coat of lacquer seems to make this stuff shrink.

Aquacoat
I don't really know if this stuff even makes it into pores, when I scrape it sideways it looks like it, it seems to lose so much volume when it dries that you need to apply at least 5 coats of this stuff. Some went into potentiometer holes and completely filled them, when the stuff actually dried what was left was maybe 15% of what it started out as. Often leaves a crackly finish that is annoying to sand out. Sands ok-ish, clogs sand paper.

Solarez
This stuff is expensive, it's a UV curing resin, but a little goes a long way. Completely fills pores up with enough body to only need one coat, dries in 30 min from exposure to UV light. Seems like a great product (until sanding) with initial results of application and how well it fills pores and how easy it is to apply. Dries in streaky, blobiness which requires a lot of sanding, sand paper loads up incredibly fast.

Both the Solarez and Aquacoat sand at much slower rates than the mahogany, so if you burn through any area, you start losing a lot of wood and not much of the filler trying to get it down which makes leveling tricky.

Anyone have tips for using these products or some other product I haven't used yet? Pore-o-Pac? Advice for what I'm doing wrong? Apply filler before sealer? Apply after?
It honestly feels like far less work to just blast the body with a super thick coat of lacquer then just sand that flat.
 
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JBG

Supporting Member
Messages
591
Are you sealing the wood before using a pore filler? Follow up: what are you using for sealer?
 

Dave Weir

Gold Supporting Member
Messages
1,222
I’ve used everything mentioned, and don’t like any of them.
Mostly I prefer to wet sand with boiled linseed oil and rottenstone until the pores are filled.
If I’m going to use a pore filler, like for a painted mahogany body, I like rustolium parks full trowel wood filler for floors.
Home Depot sells it.
It’s pretty soupy and you push it around until it starts to set. Wipe off the bulk of the excess with a putty knife. When it’s mostly looking dry, scrape with a razor blade at about a 45 until all the extra is off. Very little sanding required. The edges I wait till it’s starting to set and rub in in bare handed.
If you want a clear finish Like a lacquer you can tint it with a fair amount of trans tint dye.
 

Neverwhere

Member
Messages
608
Are you sealing the wood before using a pore filler? Follow up: what are you using for sealer?
I've tried some sealer from Stewmac, also just tried a couple coats of lacquer. I've tried applying these grain fillers both before and after a sealing coat.
 

JBG

Supporting Member
Messages
591
I used to use some oil based filler and never really liked it. These days I wet sand with naptha & force the slurry into the pores. It looks less obtrusive than some of the other fillers I've used. Once it dries you carefully wipe the excess away perpendicular to the grain with a disposable shop towel (dry). My first sealer coat (I spray catalyzed stuff) is thinned 2:1 (sealer:acetone) so it's stupid thin like water, and sprayed with barely any air pressure (so it won't blow the dried slurry from the pores). The wood/slurry soaks the sealer into itself so you can lay it on a bit for the first coat. Let it flash off a little longer to let the extra solvents evaporate, then I shoot the rest of the sealer coats with my normal 10% thinned mixture. YMMV
 

John Coloccia

Cold Supporting Member
Messages
9,580
I like thinned Timbermate, and I usually fill with one coat. I also really like using finishing resin, like the Zpoxy mentioned above. One trick if you use epoxy (and anyone who's done a lot of fiberglass work will attest to this).

It's easy to get pin holes. They'll drive you nuts. The epoxy bridges over the small pores, you sand off the top, and you get a pin hole...LOTS of them. Also, there will be some out-gassing of the epoxy for various reasons and this can cause pinholes. The trick is to heat the work piece with a hair dryer, or however is convenient. You can even GENTLY heat the epoxy after you've applied it but before removing the excess. And the key word here is GENTLY. Just little heat will greatly lower the viscosity of the epoxy. You may also see little pinholes "popping" as it warms up a bit. Then let the whole thing cool down before removing the excess. As it cools, any additional trapped air will contract and suck the epoxy into the pores. Try it on scrap. If you heat too much, you'll cause the epoxy to kick off way too quickly and it will make a horrible mess.

But at least heat the work piece if you're not confident that you can GENTLY heat the epoxy. Ideal would be to get the work pretty warm, and then to try and get the epoxy up to room temperature on a really warm day (I dunno...think like a 95 degree summer day, or something). And ideal is to do it in the evening when the temperature is dropping anyway. Give it a little time to cool, and then remove the excess.
 

JBG

Supporting Member
Messages
591
West System epoxy is really thin, too... almost TOO thin sometimes. That may be a good candidate for epoxy pore filling.
 

K-Line

Vendor
Messages
8,026
ML Campbell oil filler on ash, and tinted for mahogany. Takes a bit longer but works as I want.
 

John Coloccia

Cold Supporting Member
Messages
9,580
West System epoxy is really thin, too... almost TOO thin sometimes. That may be a good candidate for epoxy pore filling.
Yes, you're very correct. West generally doesn't have any fillers. It's just epoxy. If you want to make a structural epoxy, like the typical epoxy you'd find in a hardware store, you actually have to add some fillers. On it's own, it's terrible for the typical things most people use epoxy for. General purpose epoxy is filled with fillers of various kinds.

West would be a good choice for grain filling as well. I really like West and use it for all sorts of stuff. I usually recommend zpoxy only because it's very easy to find and very convenient. If you have West, that's a great choice too. That's generally what I have in my shop, but Zpoxy seems to sand a little bit nicer. That's just a preference. They're both great.
 

JBG

Supporting Member
Messages
591
West filler: yep. I've got a container of silica filler that I use when doing anything that's not filling knots on alder. ;) I went with them for the longer open time for certain procedures. 5 min gets tricky sometimes, especially in summer.
 

Nick Sorenson

Rocketfire Guitars
Supporting Member
Messages
996
Durabond, EZ Sand, or similar powder in a bag mix (hot mud) drywall joint compound works great believe it or not. You have to go cross grain with a plastic putty knife tool or credit card to remove most of it after it's applied. Wipe off anything you missed with the plastic tool with a damp rag when it's almost set. You don't want anything on the wood except what's in the pores. If there is anything remaining, just lightly sand it off with 180 or 220 grit. Don't sand too much or you're back to grain filling.

Give it a coat of sealer before you grain fill. Don't soak the wood with the sealer, but do wet the wood and let the sealer dry before the grain fill. Remember the idea behind grain filler is to fill the pores, you don't want to seal the wood with grain filler.

On to sealing the body with the sealer of your choice.
 

Nick Sorenson

Rocketfire Guitars
Supporting Member
Messages
996
Durabond, EZ Sand, or similar powder in a bag mix (hot mud) drywall joint compound works great believe it or not. You have to go cross grain with a plastic putty knife tool or credit card to remove most of it after it's applied. Wipe off anything you missed with the plastic tool with a damp rag when it's almost set. You don't want anything on the wood except what's in the pores. If there is anything remaining, just lightly sand it off with 180 or 220 grit. Don't sand too much or you're back to grain filling.

Give it a coat of sealer before you grain fill. Don't soak the wood with the sealer, but do wet the wood and let the sealer dry before the grain fill. Remember the idea behind grain filler is to fill the pores, you don't want to seal the wood with grain filler.

On to sealing the body with the sealer of your choice.
Oh... and in most cases you won't see the filler:



 




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