prepping the body

[seangil]

I'm building a flattop/acoustic guitar with spruce top, hog neck, and maple back & sides. I'm at the point now where I can move to applying the finish.

A couple questions...

1) Does anybody have experience with Solarez as a top finish? If yes, any tips? And what did you use underneath? Did you apply a sealer or pore filler?

2) For those who haven't used Solarez, general advice welcome on when to use a sealer and when not.

3) My understanding is that use of a pore filler depends on your choice of wood and usually not needed with softwoods, but curious if anybody uses it on spruce tops.

Thanks

[charles Tauber]

I'd not heard of Solarez products before. They make quite a range of products, all UV cured. I'm assuming this is the one you are going to use, I Can't Believe It's Not Lacquer: https://www.solarez.com/product/brus...s-not-lacquer/

I've not used their products or other UV cured finishes, so can't offer anything of value on that.

As for sealers, there are opposing opinions. One "camp" believes they are a good idea, particularly in the old days of using sanding sealers with lacquer - easier to sand than the top coat. The other "camp" sees them as unnecessary and just another layer of chemistry that can introduce incompatibilities. I've done both and don't have a strong opinion either way. I stopped using "sealers" years ago, but will, in some circumstances use a thin coat of shellac to stop Color-bleed or seal oily woods that interfere with proper drying of top coats.

As for pore fillers... As you are probably aware, woods are divided into two categories: those with "open" pores and those with "closed" pores. Those with "closed" pores have very small pores that will leave a smooth surface. Closed pore woods include maple, birch, beech and most conifers - spruce, redwood, cedar, fir...

Open pored woods have pores that are too large for "regular" finishing materials to fill. Open pored woods include white oak, rosewoods, mahogany, padauk, Spanish cedar and many others. The result, if unfilled, is a finished surface that is filled with many small pits. On a glossy surface, the pits are very obvious. It is an aesthetic choice whether or not one likes that appearance. If one does not, one fills the pores with some substance so that when the final top coat is applied (and sanded level, in many cases), the surface will be dead flat.

One can use almost anything to fill the pores of open-pored woods. Historically, people have used egg whites, plaster of Paris, wood dust, commercially prepared paste and similar other substances. In more recent years, people have used epoxy, CA glue, various water-based liquids and various UV-cured liquid coatings. After being applied, and usually levelled/sanded, top coats are then applied.

Filling the "non-existent" pores of closed pore woods is a waste of time and material. If you want a smooth, pit-free finish, you'll need to fill the open pores of the mahogany: you won't need to fill the pores for the spruce or maple.

A successful finish is a combination of the right combination of chemisty-compatible products and the right application technique. Very often, that is the result of a certain amount of trial and error. Any new combination should be tested on scrap, rather than on labour-filled work projects.

[seangil]

Hi Charles,

Thanks for your detailed response. I see that you are quite active in many of these discussion chains and also that you have been doing guitar work since the late '70s. I appreciate your being willing to share your experience.

You did find the product that I have in mind.

Your advice on open/closed-pore woods is clear that I don't need to do the spruce top. What about if you have a rosette that is made mainly from open pore woods? Would you apply the pore filler to the rosette and leave the sound board unfilled

[charles Tauber]

I use classical style rosettes. I fill them with a coat of clear 5-minute epoxy after Inlaying them, then scrape level. I do this before the sound hole is cut, but it could be done at any stage. The top coat is applied over that when the finish is applied to the top.

[PeteD]

I was intrigued by this project when I saw this on Youtube from an electric guitar builder, which you may have seen, for grain filling:

https://www.youtube.com/watch?v=405f5bAFVx0&t=176s

He goes on in an other video to show how he uses it for final finishing as well:

https://www.youtube.com/watch?v=HjK1e2nFrxw

I was planning to try it out at least for grain filling on my next build. Not sure if I would use it for the final finish coats or not...but it might be worth a shot, depending on how thick it wants to go on with some test pieces.

[seangil]

I just tried the pore finisher and will post some pictures. I have to say that I am pretty impressed, although I don't have a lot to compare against it.

I have seen guitars that used the finish. They looked good to my eye and comparable in quality any of the reasonable nitro-spray alternatives. You have to smooth it on carefully, but that is a matter of technique rather than quality of the product.

[charles Tauber]

I'm interested to see your results.

I'm curious to experiment with the product if I can get it in Canada, where I am. They seem to have a Canadian distributor.

[Howard Klepper]

Solarex has a reputation for being very stiff and brittle material when cured, and for that reason being easily cold checked or crazed from an impact. If it fills the pores, great, but I would sand back to wood. If you are finishing with nitro lacquer or shellac, there is no benefit from using a sealer--it only provides a chance of getting an adhesion problem or lack of clarity.