I'm learnin'...I just learned not to deliver an unfinished guitar. It came back with a damaged spot on the soundboard, and of course I didn't notice the damage until I started French polishing. Filling it with cyano made it look worse, so I've sanded it back to flush, thereby making a light colored spot.
Rather than sand down the entire top to a light color, I'm thinking about ways to darken the area. Exposing that spot to ultra violet light seems like one possibility, but I thought that you guys might have some better ideas.
Thanks for the quick reply!
I just remembered that baking soda (sodium bicarbonate) darkens redwood. I've got some of that up at the house, and I'll try it on some scrap of the same top.
By the way, this top came from a set of bookshelves that my wife's grandfather nailed together back in the late 1940's or early 1950's. I noticed that it was nice vertical grained stock when we moved up to Fort Bragg from Palo Alto. I built a dining room full of plywood bookshelves in exchange for it, Dave Borson resawed it into tops, and the first guitar made with the wood was bought by Daniel Roest the president of the Sacramento Guitar Society!
The fun part about the whole thing is that there are two nail holes that couldn't be avoided. I inlaid them with dots cut from the scrap, but they are still quite visible. Daniel tells the story whenever he plays a concert, and the audience gets a kick out of it!
Great story :-)
I believe this is a saturate solution ready to use. Works great on spruce. And found at any Wally World.
I went to your link and found a fish tank treatment. Is that what you use on spruce? Do you know what its active ingredients are? And what does it do to spruce?
I tried both baking soda and washing soda on a scrap of the WRC that is on the guitar, with little effect. With the washing soda I made a really strong solution in boiling water. It turned redwood a really dark brown, but barely affected the cedar.
I googled darkening wood with UV and got a bunch of references. That seems the safest way to go, since that's how the color got there in the first place. I'll shop around for a UV bulb this morning.
Yessir, weird as it may sound, it's a treatment for clearing water, and the active ingredient is potassium permanganate (stated on the label.) The purple colored Koolaid guy put up by Roger is about the same color. Any pet store stocking fish supplies should have it. About 2 bucks if I recall, and works great on spruce. I used to use TSP, (trisodium phosphate) to clean and darken oak, so that may work as well, but I don't know if cedar has enough iron content to react. Good luck. Oddly enough, I found the fish stuff on a survivalist site, but I don't recall what they were using it for.
Here's a StewMac video featuring Mamie Minch (whose dad is on this forum) on this subject.