Question on grain filling

[ram4UT]

I'm working on an acoustic guitar project, but I'm assuming the info Im looking for applies to all tonewoods.

I'm sure this had been discussed, so my apologies if it has been.

I've read on several boards that builders have used Durhams Rock Hard Water
Putty as a grain filler, as well as Bondo. But I was told no, not to use those.

I'm doing a mahogany neck and an acoustic with rosewood back and sides.

This is one recipe I was given. I'll be using gloss nitro clear coat
Mahogany neck
1. Sand
2. Stain to desired color
3. Spray two light coats of sanding sealer. I use Behlins vinyl sanding sealer.
4. Lightly scuff sand
5. Apply grain/pore filler ( if I can use Durhams, I'll color it with dye, in this
I have the brand Rockler carries. I'm using dark Walnut.
6. After grain filling and sanding to level. Apply two more lights coat of sealer,and scuff again
7. Start clear coat application.

I realize there are many different recipes and procedures, but I guess what I'm really looking for is, can I use Durhams as my filler?

How about using it for the rosewood?

I'm not staining the rosewood. I'm going straight to sealer, and then filler that has been colored. I using the same basic recipe as the mahogany, just not staining it before the filler application.


How about the top? I don't think Spruce doesn't need grain filling, but do I deal it before applying cleat coats?



Thanks guys!

[mirwa]

Rosewood needs filling, mahogany needs filling, spruce needs filling.

Cheapest and easiest way to do the filling is to mix a 2 pound cut of shellac and use the shellac for the pore filling.

Steve

[Bill McCall]

Any reason not to use commercial wood filler designed for porous woods? I'm always leery of using a product not specifically designed for the application. Of course, ymmv.

[Bill Snyder]

Rosewood needs filling, mahogany needs filling, spruce needs filling.

Cheapest and easiest way to do the filling is to mix a 2 pound cut of shellac and use the shellac for the pore filling.

Steve

I disagree that spruce needs filling. It is a closed grain wood. What is there to fill?

[michaelcj]

I'm with Bill, no fill on spruce. Nor Maple for that matter.

[sunburst]

I suspect Durham's would work fine. I've used it as a wood filler and other uses, but not as a grain filler. All sorts of "stuff" has been successfully used for grain filler on guitars including (but not limited to) pumice (traditional) drywall mud, plaster, and other things we would not normally think of as wood grain filler. In light of that, why not use Durham's? Try in on scrap, of course. As for using bondo, unless you are going to paint the guitar, I suspect it would not work well.
Your choices for rosewood are: 1.use a clear filler or 2. use a dark filler. Dying the filler is an option, buying dark filler (already dyed for you) is another.
(FWIW, my go-to grain filler for mahogany and rosewood is 2lb cut shellac mixed with acetone. It dries and builds much faster than shellac alone, and it is clear so I can have a "natural" finish color.)
(Spruce needs no filler.)

[mirwa]

I disagree that spruce needs filling. It is a closed grain wood. What is there to fill?

Well, when a guitar is built and spruce is adjacent to the rosewood, what do you use to stop the spruce from getting stained from sanding and filling and levelling the rosewood.

The use of a pore sealer is not always about filling it for subsequent coats of lacquer, its also used for protecting a surface from being stained.

The replies make me wonder whether others have actually built a guitar with rosewood sides and a spruce top.

Steve

[sunburst]

Sealing and filling are not necessarily the same thing.
Grain can be filled without being sealed (but not usually) and wood can be sealed with no grain filling.

[mirwa]

John - semantics

Steve

[Tavy]

John - semantics

Steve

I'm sorry no it's not - John is spot on here. A sealer coat will do exactly that - seal the wood and protect it from getting stained, prepare it for final sanding and finishing. It does not fill any wood pores.

Pore fillers are typically quite different - often high is solids, and/or full of stuff that would do the acoustics of a fine spruce top no good at all.

There are crossovers of course - you can use almost any finish/sealer including shellac as a pore filler by sanding it into the surface - in that situation the finish is just a binder, and it's the wood dust that acts as pore filler.

To get back to the original question... I have one criticism of the original proposed method: if you plan on sanding anything that has been dyed, expect to sand the dye partly off and end up with a blotchy color. IMO if you're using a filler then best not to dye the wood unless you're planning to do a lot of experimenting first. Alternatively, since the Mahogany typically doesn't need much in the way of filling anyway, you could just wet sand the sanding sealer into the wood (ie using the sealer as lubricant), level sand, and call it done. The Rosewood is a different animal though... use a filler if you can.

[mirwa]

I'm sorry no it's not - John is spot on here. .

I sometimes wonder why people feel the need to be so aggressive in a response, far better to say, I actually find something different, or I believe it to be this way.

This is a far better response IMHO, as it states a matter of opinion and then asks for discussion.

I disagree that spruce needs filling. It is a closed grain wood. What is there to fill?

Bill, I actually agree with you, spruce is a closed grain wood and in general does not require any filling or sealing, have painted many spruce tops with no fill, my original statement on this one, as the OP is building a guitar with rosewood and spruce, is more to do with protecting the top from being stained and discoloured during the build / sanding process.

Back to your comment Tavy.

A sealer coat will do exactly that - seal the wood and protect it from getting stained, prepare it for final sanding and finishing. It does not fill any wood pores.

Interesting, so your saying using shellac as a sealer does not in anyway fill the pores of the wood, that's a new one for me. I wonder what i was doing wrong all those years when I French polished tops with shellac, if the shellac doesn't fill the grain, defies logic that I managed to get a mirror finish on the grain, almost as if the grain had been filled with shellac. Or when I used shellac as a sealer and then painted straight onto it, the sealer seemed to fill the pores of the wood so my paint would not soak into the grain.

For anyone that has built a guitar, they know you cannot sand rosewood connected to spruce without first sealing the spruce, I did not feel the need to clarify seal or fill to the original poster, they started the heading of the topic as filling, I understood what they were referring too, i am sure they also under stood what I meant as well and if they did not, then possibly they may have asked, hey why am I also filling the spruce, which would have lead to the discussion without the negative connatation.

Semantics is refrerring to that requirement to clarify, it's really not necessary to clarify the terminology.

You don't want to fill spruce, well that's great for you, I will fill / seal or whatever you want to clarify the definition to be, the spruce, so I don't stain the spruce when sanding, I know this from having built rosewood spruce guitars as I am sure every person who has built one also knows.

Steve

Some of my paint work

http://www.mirwa.com.au/Painting.html

A walk guide on how to actually paint

http://www.mirwa.com.au/HTS_Paint.html

[Bluetickhound]

I've seen people who have used 2 part epoxy to fill grain. Mix a small (and I mean SMALL!) batch, squeegee it in with a razor blade... Wash, rinse, repeat... I bet it's very time consuming but also very effective. Once the epoxy sets up its hard as a rock. In my limited experience all I've ever used is a couple of wash coats of 2# cut and pumice. Again, time consuming but it works for me.

[Vernon Hughes]

Jasco make a great pore filler.

[dschonbrun]

Sounds like a lot of semantics and emotions here.

Instead of focusing on the terms, perhaps it would be helpful to define the problem each luthier is trying to solve, and then discuss options? That might be more fruitful.

D

[sunburst]

I've seen people who have used 2 part epoxy to fill grain.

Forgot about that. I've used epoxy to fill a couple of guitars (neck, back, sides) and it worked very well. Squeegee it on, let it cure, sand back to the wood surface. It actually sands surprisingly well. The thing to watch is: sanding must stop exactly when the surface of the wood is reached. Any further sanding reopens pores.

[Stephen Perry]

This is an interesting discussion. I'm more of a violin guy, although I seem to spend more time working on mandolins these days. Rather than thinking of this filler or that, violin folks tend to think of a system of finishing and how the parts will work together. The old Byzantine pattern passed along likely by monks spreading through Europe and bringing knowledge of the Roman ways proves a useful example:

1. Primer - penetrates the wood and prepares it.
2. Sealer - prevents penetration
3. Ground - levels and prepares for adhesion.
4. Paint - I include transparent finishes with color
5. Varnish - clear or clearish top coat

I see the discussion of sealer and filler above to be like the sealer and ground discussion in violins. One aspect not addressed in the above is the acoustic effect of various materials.

1. Primer. I don't see that in the mandolin / guitar world. Various magic stuff. Salt of gems. Borax. I'll put other wood treatments in here. Heating. Humidity cycling. Cryogenics. I also in my thinking add surface preparation. Washing out dust and debris, if any, and smoothing. In my odd 17th C world, I use scrapers to do the final leveling after priming. no paper except the neck and edges of the plates. On the acoustic front, treatments such as borax deepen and somewhat darken the tone of a plate. I would like to think this is good and shows up in the final instrument as a moody undercurrent, but I have absolutely no evidence of that! Borax does keep the bugs out, so I use it lightly, as distinguished from boiling in some kind of magic bath!!! Although perhaps pressure cooking with chemicals would be a reasonable production method. There's also coloring of the wood as part of this stage. UV. Chemical agents.

2. Sealer. This is starting to get to where the audible effects are very clear. Some evidence suggests plant gums were used by at least some old makers. I have used gum arabic, diluted, very little. This gets a nicely focused sound. The goal isn't to fill, just to keep everything else out of the wood. I've also used shellac, casein, vernice bianca, and very thinned water based poly varnish (which may well be the best). The deepening of the primer is enhanced by this, and the mid range sounds as if it's coming into focus.

3. Ground. Here we go, read everyone and weep. The ground seals. Too many formulas. I rub the instrument out lightly with pumice in a bag, packing a bit of mineral in the pores. Not very much - just to level the faint rising of things from the sealer. Dust off and then use a mineral-laced liquid / slurry. My current choice is aerosil, I think, very very fine material. I've used the Rubio ground, rottenstone, pumice, fused glass powder. I'd like to use very fine diamond dust just because. Vehicle can be an emulsion of some type, casein, gum arabic, shellac, oil varnish, spirit varnish, modern poly varnish. The goal is to get a sealed and suitably leveled surface that will not absorb color. The ground has a remarkable effect on the tapped tone character of thin plates.

4. Color coats. Here's where the mandolin / guitar crowd usually goes for hard stuff, and I stick with soft stuff. Any kind of colored varnish will do. Not too much. Thick hard finishes obviously hurt things. I've actually spent hours scraping down violins with modern thick overcoats, and using various chemicals, all to get back to the original varnish, even if the varnish is fragmentary. My opinion is that varnish wears through, so what? I have my fiddle from 2002 that has crackled, worn through in places, and looks great! It's a mastic and oil based stuff stained with powdered pigment mulled in. Didn't change the sound at all to put it on.

5. Varnish. Clear stuff on top. No harder than what's underneath. I usually dispense with this.

And OF COURSE, this is exactly how I would finish a mandolin were I to get around to making one!

[Tavy]

I sometimes wonder why people feel the need to be so aggressive in a response, far better to say, I actually find something different, or I believe it to be this way.

I apologise if I came across that way, not at all what I intended - funny old medium the internet isn't it?

Back to your comment Tavy.

Interesting, so your saying using shellac as a sealer does not in anyway fill the pores of the wood, that's a new one for me. I wonder what i was doing wrong all those years when I French polished tops with shellac, if the shellac doesn't fill the grain, defies logic that I managed to get a mirror finish on the grain, almost as if the grain had been filled with shellac. Or when I used shellac as a sealer and then painted straight onto it, the sealer seemed to fill the pores of the wood so my paint would not soak into the grain.

I think we're talking about quite different things here.... if you're French polishing all the way, then on a very porus wood such as rosewood there is generally a specific grain filling step involving pumice or other abrasives. And yes, there is a certain amount of "packing down" of shellac into the pores, but there is also wood dust kicked up which does most of the actual filling IMO.

But we've got way off topic for the OP. To be clear the thing I was flat out disagreeing with was your assertion that spruce needs "filling": looking at the links you gave, I can perhaps see some logic behind that for flat-colour solid bodied instruments, but not acoustics IMO which is what we're talking about here. My concern on reading your post, was that a newbe would read that and go off and smother their nice spruce top with some random commercial pore filler (epoxy anyone?), and then wonder why their mandolin sounds like a lump of lead I'm sure that's not what you were suggesting folks should do, but like I said, funny old medium this written word thing...

[Jim Adwell]

I don't think anyone has mentioned using CA glue to fill pores.

[Bill Snyder]

I don't think anyone has mentioned using CA glue to fill pores.

I have done that on a rosewood peghead veneer. The fumes can get a bit strong

[Tavy]

I have done that on a rosewood peghead veneer. The fumes can get a bit strong

Indeed, it does work very well... just don't use it (or possibly any filler) under EnduroVar or it will peel right off... don't ask me how I know!

[Jim Adwell]

I've not used it for pore filling, but this UFO CA from Satellite City is pretty much odorless and non-irritating. It does take a little longer to cure, though, and it's relatively expensive.