How to keep the natural walnut color. No darkening.

[asa_low12]

This is my first guitar build (technically my second, but I abandoned the first and immediately started this one). The walnut that it’s built from has sentimental value and the particular boards and tree they came from go back to my great grandpa that died before I was born. This was “his favorite tree on the farm”, back behind the garden, until it got hit by lightning in the early 70’s. My dad and uncle and grandpa sawed it up into boards for him back then and they have sat in his house that’s falling down this whole time. My dad had a dulcimer made for my mom out of it back in the early 80’s. Anyway, I decided two summers ago to build a guitar for it from my dad. He doesn’t really play but he tries occasionally. It won’t get played much, it’s more of a sentimental guitar and practice for me. I took a long break from it but decided to start again. I made a lot of progress and am about ready to finish sanding it and put a finish on. I was planning on tru oil, but you can see from the sample piece how much it darkened it. The end grain is basically black. All I had were 1x6” boards for this and the body is 9 pieces and I worked hard to match the grain and am afraid if it darkens like that on the sides then it will show a lot more where it doesn’t match as well. What would be the best finish to basically just protect it with the color it is now and not darken it or what will change it the least? I can spray, it doesn’t have to be an oil finish.

 

[ale.istotle]

First, that's really beautiful. Nicely done.

I'm not aware of a transparent finishing technique that will be lighter than the wood is when you wet it. The look of the true oil is pretty close to wetting it with mineral spirits. You can try different finishes on scrap - true oil vs wipe on poly vs water based poly but i think you are going to get that classic dark walnut color regardless. It's just what the wood is.
Some of the finishing pro's on here may be able to recommend something of a blonde or washed transparent finish maybe but that's outside of my experience.

Good luck.

 

[Peegoo]

Clear finish penetrating into wood leads to darkening the color. The best thing to do is use something that seals the wood without penetrating it too much. Aerosol shellac, sprayed from about 14" to 16" is one way to do this because much of the solvent/vehicle evaporates before it lands on the wood. Use several very light applications (a hazy look) with dry time between.

You can follow with several coats of Tru Oil and then level sand.

Most important: practice this on scrap wood first.

 

[ponce]

Time. My experience is that walnut gets brighter with time under the clear finish.

 

[stratisfied]

A water-based polyurethane, acrylic lacquer or 2K clearcoat will change the appearance the least but will still deepen the color slightly. Any oil based product will darken the wood significantly.

 

[loopfinding]

first thought was water poly

 

[Jim_in_PA]

Just be aware that most waterborne finishes make walnut look very "cold"...blue-ish sometimes. Do a test piece first to be sure it's what you want the look to be. A light coat of wax-free shellac first will add just a touch of amber that will warm things up a hair without dramatically changing the "darkness" of the finish. And yes, walnut tends to get lighter in color over time from UV and oxidation, unlike many other species that tend to get darker over time.

 

[schmee]

My guess is a water based very light coat first. Or as mentioned aerosol shellac that dries super fast. You want to seal the wood before it gets penetrated.
It will work only marginally though probably. I was very surprised when my daughter asked me to use water based on some new oak stair railing how light it dried.... even though it takes forever to dry.
Maybe even just quick wiping shellac on with a rag? Trouble is you could get uneven overlaps...

 

[ponce]

You could try to 'whiten' the endgrain parts with NaOCl or H2O2 or similar, prior to finishing.
It worked on yellowed spruce for me.

 

[pfarrell]

Happened upon this thread (beautiful wood on your guitar!)... I think your answer is a floor finish called Bona. Their finishes are amazing—2 part waterbourne—have to buy via a commercial source most likely, though I have seen it available on Amazon of all places. Freakishly hard, and extremely matte options (satin and semi are the others). Their specialty is finishes that look like "no finish" on raw woods—Check out the "Traffic" line, specifically "Naturale". They have a some competitors now—but my understanding is they invented the space/chemistry. It's on our floors—I wouldn't hesitate to put it on furniture—they do not do high gloss though... But I think your guitar in matte would be exceptional—also, that matte finish won't build any gloss over time in use areas... or my floors would have glossy spots..... (yes, same company that makes the cleaning products.)