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  #1  
Old 03-27-2018, 03:24 PM
TEK TEK is offline
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Default A question for the Wood Professionals here

I have some Wenge that I am building a guitar with and it has some spots on it. I did not pay that much attention to the but now I am getting to the finish stage of the guitar and I am not sure what to do.
The "spots " are on both sides of the back boards (inside and out) and do not sand or scrape off. I tried putting a little stain on them but they don't take the stain. I put a little shellac over some and of coarse they show up terrible.
Any suggestions?

bare wood, sanded


This picture has a little shellac over top.


Any suggestions would be much appreciated.
Thanks
Travis
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Old 03-27-2018, 03:43 PM
printer2 printer2 is offline
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Quote:
check for mineral deposits (recognisable as white dots next to
each other in the pores) as these deposits can only be removed with a great deal of effort
https://www.hesse-lignal.de/fileadmi...n_Wenge_EN.pdf

I can't find what to do about them.
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Old 03-27-2018, 05:09 PM
surveyor surveyor is offline
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Do those "spots" appear to go through the wood and appear in the same position on top and bottom? If they do , I don't think there is any chance you can sand them out. If you have a cut off with some of the same spots you might experiment with different dyes or maybe vinegar and steel wool/rust to see if they still show up.
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Old 03-27-2018, 09:00 PM
printer2 printer2 is offline
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The only thing I read is to try scraping it away, tough with the pores.
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Old 03-27-2018, 09:41 PM
John Arnold John Arnold is offline
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white vinegar
C-L-R
muriatic acid
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Old 03-28-2018, 05:55 AM
kjaffrey kjaffrey is offline
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They look like mineral deposits to me also And Johns sugggestion is exactly what I have used in the same order, vinegar, CLR (Calcium Line Rust bathroom cleaner) and then if all else fails muriatic acid (which is really hardware store hydrochloric acid, just dilute it with some water first).

Kent
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Old 03-28-2018, 08:38 AM
TEK TEK is offline
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Thanks everyone for the replies. I assumed they were mineral deposits. They did not scrape away.
I will try CLR , muriatic acid or vinegar and see what happens.
I appreciate the input.
Travis
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Old 03-28-2018, 09:05 AM
arie arie is offline
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if you're going to dilute your acid always add your acid to the water, not the other way around.

in case you weren't sure
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Old 03-28-2018, 11:27 AM
TEK TEK is offline
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Thanks for the heads up Arie
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Old 03-28-2018, 04:59 PM
Wozer Wozer is offline
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I have doubts that those are mineral deposits...the ones I've seen have been in the pores only. Either way, it's certainly worth a try to see if they can be removed.

I'm leaning more in the direction of some sort of contamination caused by water dripping on the billet before it was resawn. For example, if Mahogany is left under a leaky galvanized metal roof the result will be a lot of black spots all over the place. I forget the specific chemical used to deal with it, but there is one (and yeah, I used it to be able to use some custom milled Mahogany...it was far cheaper to repair than have new materials milled up)
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Old 03-29-2018, 03:27 AM
mirwa mirwa is offline
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Maybe you may need to mix a diluted stain up to try and smooth its appearance out.

Steve
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  #12  
Old 04-04-2018, 11:34 AM
TEK TEK is offline
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I have tried white vinegar, CLR, and muriatic acid. Nothing seems to change the spots. I put a drop of dye on a spot on a piece of scrap and all it did was color around the spot.
When the back is sanded and sets overnight the spots don't show much. As soon as I wet it with naptha, the spots jump out everywhere.
Any other suggestions, other than not to build with this piece? Its a little late for that suggestion
Travis
Here is a picture of the back and a closeup of the spots.

Last edited by TEK; 04-04-2018 at 01:15 PM.
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  #13  
Old 04-04-2018, 12:29 PM
Truckjohn Truckjohn is offline
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If it's not taking a water/alcohol based dye - try an oil based stain.. Perhaps even a dark walnut or brown mahogany gel stain - they tend to go on gooey and lay on top more than soak in...... You may have to stain all the Wenge to make it look right. Then once you get it right - seal with shellac to make sure it doesn't wash out during finishing..

If all else fails - paint it black and call it a "Premium" stage finish.
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  #14  
Old 04-04-2018, 12:48 PM
nikpearson nikpearson is offline
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Default A couple of suggestions...

I’m far from an experienced builder but a couple of things you could try are:

Use high opacity wood touch paints and feather in the edges around the spots. You may even be able to simulate the wenge grain using different shades and a very fine brush. These paints stick to pretty much anything and the solvent is a cellulose thinner type.

The other alternative I can think of would be earth pigment suspended in shellac. One of my tutors uses this for a variety of fine touch up work.

Both of these suggestions are going to take a lot of time and will need to be applied after sanding but before the final finish.
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  #15  
Old 04-04-2018, 01:29 PM
TEK TEK is offline
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Thanks for the suggestions John and Nik.
I will try the oil based stain and see what happens and if all else fails I will "paint some grain over them".
It is a shame because I thought the guitar was looking pretty good up until now.
The wood in these pictures is "dry".



Last edited by TEK; 04-04-2018 at 04:58 PM.
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