grain filler for mahogany guitar

[jack620]

Hi All,
I'm building a mahogany acoustic guitar from a Stewart Macdonald kit. I intend to spray the guitar with Mirotone 3220 pre-cat lacquer. The mahogany has a fairly open grain which I would like to fill to get a glassy finish. I tried the Walnut colour Timbermate on a piece of scrap but I don't like the result. It has a purplish hue from some angles and it dulls the look of the timber. Timbermate's mahogany coloured filler looks way too red so I haven't even tried it.

Mirotone make a walnut coloured spirit-based wipe-on/wipe off grain filler, but it only comes in 4L cans. I see Wattyl make a neutral colour wipe on/wipe off grain filler that comes in 375g cans, but you have to tint it yourself.

I guess I could also skip the grain filler and build up layers of Mirotone and sand it back until the grain is filled. I will be getting a 4L can so I will have plenty of product.

I only have one more small piece of mahogany off-cut, so I don't have the luxury of trialling a dozen different products/techniques. Can anyone suggest a suitable product or technique? Thanks

[Christos]

I see that not many people have replied to this thread, So Far. I have no experience with what you are asking for so my advise is only a thought.

Are you able to use sanding sealer and then sand back to bear wood.

Your question would be will it fill the pores before the first coat of your required finish? I am not sure.


Might be best to get some more Mahogany and practice on that.

[bassbuilderman]

Hi Jack620,
Perhaps posting this is the Musical Instrument section might get you a better response.
Any reason you didn't go for the Stewmac medium brown waterbase grain filler. This should be good for your purpose.
BBM

[jack620]

thanks for the responses guys. I've heard that sanding sealers aren't totally clear and can dull the finish if used to grain fill.

I was given the kit as a gift. I guess I could order the Stew Mac grain filler but the cost with postage would be a bit excessive. Bunnings sell a waterbased filler called Red Enz who have a walnut filler that is more brown and less purplish than the Timbermate one. I'll give it a go. I might also move this thread to the Musical Instrument forum as you suggest.

Cheers.

[Sebastiaan56]

Hi Jack,

There are plenty of threads on the net on using epoxy as a grain filler. I use the West Systems, see http://www.carbatec.com.au/pdf/catalogue/216.pdf as it seems to be the clearest. It takes a couple of applications but sands back very well and really pops the grain. I use a very stiff business card or an old credit card (the ones that AMEX send in the mail with John Citizen on them are great) and I put on just enough to fill the holes. Mahogany will probably take two coats. There are plenty of tutorials on the net, try the Official Luthiers Forum.

Just be aware of the safety issues with epoxy, they probably apply more to frequent users but it can cause severe allergic reactions. Avoid skin contact and inhaling the dust and hardener where possible.

[jack620]

Thanks for the info. I'll check out the epoxy option

[KJ401]

Reckon you've already picked up this from one of the music threads, but be very careful using epoxy or 2 packs (anything that has a catalysing hardener) on musical instruments that require movement of a sound board or other parts of the instrument for resonance.

Stiff inflexible coatings or finishes will dull, mute, muddy the sound - particularly with guitars and string instruments. Many a 'cheaper' guitar can be turned into a surprisingly good instrument by gently stripping off the factory gloop and refinishing with nitro or pre-cat lacquer.

Mahogany will take a lot of time and precat to choke. There are lots of suggestions for fillers on the music forum; you can also 'soup' the finish. Put a few thin coast on, and within 12 hours cut it lightly, make a rubber as you do for shellac, thin so pre-cat1:1 with thinners, dip your rubber in and work the surface - it can get very very messy and sticky and will probably look dreadful. You want to push the lacquer into the grain. Don't use the rubber too wet or too long in the one spot it will 'burn' the finish you'd sprayed on ( basically the solvent will cut through to the timber). Make sure you try to pull the lacquer with the grain as you come to the end of the rubbering.

Let it sit a couple of days, and then cut it pretty aggressively. Cut out the ropey rubber marks, swirls etc - this is about filling the grain, not achieving your finished topcoat. Go back to your gun for that.

I suspect Mirotone no longer recommend souping - it's a little old-fashioned as a lacquering technique and might breach a few OH&S rules.... but don't use sanding sealer - lacquers loaded with sterates which will give a grey whitish cast, not flex enough and have low shatter threshold.

[jack620]

Thanks. I got a small tub of walnut colour Red Devil Eezee filler today. The colour is much more realistic than the Timbermate walnut. This time I tried putting on a very thin coat of lacquer (from a spray can) as a sealer. I found it very difficult to sand back the grain filler. I was using 240 grit fre-cut paper but it clogged up very quickly. I went thru a whole sheet just sanding a 150x75 piece of mahogany. Whether this is because of the grain filler or the sealer coat I'm not sure. I'll try the filler without a sealer coat tomorrow.

[kiwigeo]

Reckon you've already picked up this from one of the music threads, but be very careful using epoxy or 2 packs (anything that has a catalysing hardener) on musical instruments that require movement of a sound board or other parts of the instrument for resonance.

.

Acoustic tops are generally not made using open pored woods so pore filling is not necessary. The use of epoxy resin pore filler on the back and sides of an acoustic will not significantly affect the sound of the instrument.