grain filling, only uk method

simon1138 · 2 Sep 2020

Hello,
I am trying to build a guitar. i have the body and it is fine, now i have to grain fill it. it is a practice piece and i have already removed a few coats of different things that dont seem to work.
does anyone have a method of grain filling that is quick and as cheap as possible. please do not mention aqua clear coat as it is very expensive. i have tried a slurry method using boiled linseed oil and wet/dry paper. that did not work. i have tried boiled linseed oil and powdered wood filler, mix to a paste and smooth in. that does not seem to work. i have bought a wood filler paste from toolstation Everbuild Multi-Purpose Premium Joiners Grade Wood Filler
i water this down to a paste and smooth on with the grain and sand down. it seems to sink. i have seen rustins grain filler but that is an oil based, which apparently does not last too long and will maybe do one or two guitar bodies at most. i would prefer an easy to get, cheap and quick method.
the slurry method must work as others seem to use it with great effect. i dont know what i am doing wrong. i sanded from 80 to 320, then with 1200 and oil to get a brown sludge. smoothed on with the grain and removed excess. it seemed to sink and was still wet the morning after. the wood paste dries quick, sinks a bit. so either way i am guessing a few coats.
any help/advice would be great thanks
simon

samhay · 2 Sep 2020

What type of timber are you filling?
I'm quite fond of the BLO slurry method, but I don't think it will work well on oily woods like rosewood.

novocaine · 2 Sep 2020

1200 is way to fine for grain filling, 600-800 tops then clean it down and leave it to dry before you fill the grain.
I've used a sanding sealer (something like rustins). I've also used epoxy body filler with a tint. it very much depends on what you coating is going to be.
if you intent to oil and wax it then a shallac sanding sealing is best, if you are spray finishing it then epoxy works.

once you've sealed/filled it you need to sand it down again, this time you can go up to 1000 grit.

the last guitar I made I didn't fill the grain at all, I wet it and sanded it then wet it again at high grit, the stained it and finished it with a spray on clear coat.

simon1138 · 2 Sep 2020

thanks for your replies. i think the wood i am using is oak. it was in a skip, large oak worktop. i want to spray paint it so the finish is not natural wood, one solid colour non transparent. i am not to fussed about seeing the oil. i just want a method to get rid of the grain. i sprayed some white paint over the wood based filler i applied and the grain is still visible but not as much. do i have to remove the paint to add another layer of wood filler or can i just apply it over the paint?
the backward and forward of this is getting to me. i have not been doing it long and lack the patience of finishing. i watched a brad angove video on youtube on grain filling where he uses a wood putty, watered down to a double cream consistency and smoothed on with a plastic spatula. then wiped off straight away. that seems the fastest and cheapest method.

thick_mike · 2 Sep 2020

You are looking for sanding sealer. If you are painting over the top rather than having the wood visible, then I’d look at an auto spray can sanding sealer (look for one that is suitable for plastics and you can be sure it will have a little flex). I’ve been out of the trade too long to recommend a specific brand.

profchris · 2 Sep 2020

I'm guessing this is an electric guitar? I made a nice acoustic ukulele from oak, and will probably make a guitar one day, but the painting etc says electric to me.

Oak has huge pores, and any filler will shrink, so you will need several applications. Sand back after each one is dry and has shrunk. The whole operation will take days, maybe weeks!

US builders often use drywall compound, even on acoustics, and get good results. Apparently in the UK this is called "joint filler". B&Q will sell you 12.5kg for £3, I can't see you getting any cheaper! You can add dye or pigment if you want a colour contrast. I've read this only takes about two applications to get you level as it doesn't shrink much.

For acoustic instruments I give them 2 or 3 coats of shellac, then sprinkle on a *very* little pumice powder and work it onto the surface with a cotton pad wetted with more shellac. Two or three applications gets the grain close to filled, but I'll probably go to five or 6 on my next build. Sand very lightly between applications to level back the surface. This gives a very natural appearance to the wood, and takes maybe 20 mins per application for a guitar, 10 mins for a uke. Based on French Polishing grain filling, but a lot simpler (and probably not so good, but simple is favourite).