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Chris Knowlton

Correcting a light spot

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Hello All,

After applying the third thin coat of sealer I noticed what turned out to be a small dot of glue that I had apparently scraped flat but did not totally remove. It was quite obvious so I decided that I should remove it, which I did using much care. As you can see the wood under the glue is lighter than the surrounding tanned wood. If I return the violin to the light box, can I expect this light area to darken and catch up with the rest of the violin?

post-24557-1278163105_thumb.jpg

Thanks,

Chris

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If I return the violin to the light box, can I expect this light area to darken and catch up with the rest of the violin?

I think it will - the rate of change in the lighter spot will be faster than elsewhere.

If you decide to return to the light box, you could blend that spot by removing some of the surrounding colour subtly before UV treatment.

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Interesting, when gluing fronts and back on, I tend to use hot water on a brush to removed all traces of glue.

This tends to raise the grain but I can live with that.

You could just retouch the area with some very strong instant coffee, or similar.

Looks like a superb violin Chris.

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Nice instrument!

I would scrap the ligher area and give some strong tea over it, but still keeping it lighter in colour. If you put it back in the UV box the rest of the instrument may get darker too, and the light spot can remain there, I think.

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The rate of tanning in a UV box is not linear, it is rapid at first and then slower later. The tanned parts will darken, but much more slowly.

Empirical observations, rather than theory.

----------------

A lttle later...

The most reactive wood I have wxperienced was a piece of big-laf maple from Canada that changed from white to an beautiful deep orange-brown with about 8 hours of sun, but changed little, if at all, after that.

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Hello All,

After applying the third thin coat of sealer I noticed what turned out to be a small dot of glue that I had apparently scraped flat but did not totally remove. It was quite obvious so I decided that I should remove it, which I did using much care. As you can see the wood under the glue is lighter than the surrounding tanned wood. If I return the violin to the light box, can I expect this light area to darken and catch up with the rest of the violin?

post-24557-1278163105_thumb.jpg

Thanks,

Chris

Nice tan hope you used plenty of sun blocker :)

You might try water colors as described in Brian Epp's new book

THE ART OF VIOLIN RETOUCHING

by Brian Epp, First Edition.

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Interesting, when gluing fronts and back on, I tend to use hot water on a brush to removed all traces of glue.

This tends to raise the grain but I can live with that.

You could just retouch the area with some very strong instant coffee, or similar.

Looks like a superb violin Chris.

Yep-- I had a major glue-spot, that I thought I had removed, and then found I had not...hot water, carefully rubbed in and out, then re-sealed, etc. (My ground and seal has color, and it re-stained perfectly.)

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Thank you Janito, Ben, Manfio, Homey, Michael, and Chet.

You have offered a lot of good ideas, and thank you for your kind words. I checked out Brian Epp’s book which looks very interesting. I will definitely put that on my gift list.

I am tempted to go with tea but I am afraid that it might wick under the sealer outside the immediate area, also I am unsure that I could match the color.

I agree that the tanning appears to have more effect early in the process, so I will give the light box time to work. If that does not work I will probably follow Chet’s process.

Thanks again,

Chris

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Honestly, I would just leave it alone and proceed as you would.

Experience has shown me that the more you "eff" with little spots like that, the worse they get. And once you start really adding color, that might be the least of you worries.

If you do a good job with your colored varnish, then no one will notice.

And if they do? Screw em. Tell them you did it on purpose, and do a better job the next time.

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Leave it until the next to last varnish coat. On the coat prior to the last, once the overall base color has been achieved, simply use either Windsor or liqutex artist paint diluted with spit. Burnt Umber should do it, depending. Mixed with spit diluted way down, you can just touch the spot with a brush to add a dash of color, let it set for 30 sec-1 min and then lightly feather the spot with a dusting brush. Create a test blank with a similar situation to practice on if you are so inclined, a small dot of glue coated with shellac will mimic the situation. sometimes a stronger, "one shot dot" is best, or sometimes several very thin spit/paint coats work best. It somewhat depends on the grain and varnish color.After it is painted in, simply apply your final coat on top and it will lock the color spot in underneath the final coat, thus protecting it and allowing for the sheen to appear correct.

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Also, this is why many will use a light glue or gelatin "wash" as a first coat. Think of glue/gel coats as a "water based" sealer. These are lighter color sealers compared to oil or shellac, which are amber. Water Based polyurethanes for Trim and floor work have the similar issue. When doing hardwood floors, for example, if one goes to refinish a floor that had a water based sealer as the first coat, and they do not sand it deep enough, and then apply a oil based or shellac sealer as the first coat, a very bad thing happens where "white" spots where the old water sealer was not removed will show. by using a glue wash as a first coat, even if very light, it will not allow the "glue spot" thing to happen.

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It took three weeks in the light box but the scraped area did finally catch up in color to the surrounding wood. I did not mask the area rather I simply exposed the full violin to the light.

Here are before and after shots.

Chris

post-24557-1280081224_thumb.jpg

post-24557-1280081280_thumb.jpg

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Hello All,

After applying the third thin coat of sealer I noticed what turned out to be a small dot of glue that I had apparently scraped flat but did not totally remove. It was quite obvious so I decided that I should remove it, which I did using much care. As you can see the wood under the glue is lighter than the surrounding tanned wood. If I return the violin to the light box, can I expect this light area to darken and catch up with the rest of the violin?

post-24557-1278163105_thumb.jpg

Thanks,

Chris

I have found that a little warm water on the glue helps get it off, and that Old Wood 1700 Golden Ground solution A can quickly brings up the color in the spot, usually overnight with UV exposure. May take several coats to match the rest of the area. It is superficial, unlike a stain, and pretty easy to rework. Light exposure alone would expect to take longer. Curious if others have used Old Wood grounds to touch up scratches etc.

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Chris, I assume this one is long since completed. Could you post an update for us? Beautiful instrument. What kind of maple...from where?

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Looking at the envious quality of workmanship I'm curious why the simple task of reducing the corners to the typical thin edge, or at least rounded/tapered. That spot? Looks my best varnishing-

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