Gray spots on maple stock after blushing.

[nchunter]

I just finished scraping my stock. I applied nitric acid, and everything looked great. However, when I blushed it with the heat gun some funny gray spots appeared in random places.

I only used scrapers, no sandpaper or steel wool, so I don't think it's foreign matter. I'm thinking maybe it's mold spores internal to the wood perhaps?  Has anyone ever seen this?

 I know a photo would be immensely helpful to this discussion, but I don't have a computer anymore, just a phone.

[nchunter]

Okay, I'm trying Tinypic via my iPhone, let's see if this photo shows:

[Ky-Flinter]

NC,

I don't know what it is, but it looks like something splashed or sprayed on the stock.  Some of the spots look directional.  I think I've been watching too much NCIS.

-Ron

[EC121]

The end grain also picked it up.

[KLMoors]

I had this happen many years ago to an entire load of custom cut trim for a 6000 sq. ft. house. It ALL had this here and there through the wood. It would never have shown up if the wood was being painted. But, of course this house had clear finish on the trim. Luckily it was discovered while back priming the trim with a clear seal coat.  It all had to go back and was replaced.  If I remember correctly, it was determined to be a mold of some kind.

Coincidentally, the gun I am working on now has had a very weird reaction to drips of sweat. Everywhere I have dripped onto it, it turns a bluish grey color.  I am guessing some type of mineral is in the wood. This commonly happens with red oak, but I haven't had it happen with maple. 

I'm not sure what to suggest for yours. Do you have any scraps that you could experiment on?

[nchunter]

Yes, I do have a practice board from the same blank as the stock. When I looked closely at it I see that it has it too in spots. I rasped down one of the bad spots, coated it when nitric acid and re-blushed it and the spots did not reappear.

I wanted to finish this stock blonde with just the nitric acid stain, but I guess I'll have to stain it dark with aniline dyes. 

[bob in the woods]

I've stained stocks pretty dark with nitric/iron alone. Under the finish , I don't believe that the grey stains you've shown would look like anything more than "character" in the wood. It wouldn't be discernible as grey IMO. I haven't had great results with aniline dyes, experiencing fading over time.

[nchunter]

Well I planed down the whole practice board and tried the nitric acid/heat again. This time gray spots showed up in new locations. So I guess it's mold within the wood or my cousin (lifelong carpenter) suggested maybe iron.

I agree about the dyes. I'm playing with them now and they really muddy up the chatoyance.

[Acer Saccharum]

I suspect that the spots won't be a problem, unless you are trying for a light honey maple.

I had a bit of heart wood in the stock, and was concerned about it showing in the finished product.


Needless to say, it made not a whit of difference, but I did not know it before staining:

[nchunter]

Acer, what stain(s) did you use?

[Dan Fruth]

I have had good experience with wood bleach before. You might try a 2 part bleach available at most places like woodworkers supply, or give clorox bleach a try...I would try it on your practice piece first......Just a thought...........Dan

[Acer Saccharum]

Acer, what stain(s) did you use?

nc, I used a light AF and followed with a spirit varnish of Dragon's Blood and Shellac. I essentially French polished the color on ( see youtube for French polish)

[brobb]

In marine work, any place there is a break in the varnish film turns grey like this.  I just bleached the wood with oxalic something or nother. 
Finish as you have planned.  Good luck

[Keb]

Coincidentally, the gun I am working on now has had a very weird reaction to drips of sweat. Everywhere I have dripped onto it, it turns a bluish grey color.  I am guessing some type of mineral is in the wood. This commonly happens with red oak, but I haven't had it happen with maple.

I've had cherry turn blue when sweat dripped on it. I've had it happen often. I always removed the discoloration before finishing so I don't know what happens when it's left on.

[KLMoors]

Thanks Keb. I'm going to experiment on my scraps to see what I need to do.