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Shunyata

Using Potassium Nitrite

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In my tests with a 4% solution, I am seeing a marked color difference between the spruce (darker tanning) and the maple (lighter tanning). I assume this difference  is due to the different water absorption between the two woods.

The tanned maple is about the same color as the inside of my 100 yr old violin - maybe just a shade lighter.  The red spruce is a little darker, with a pronounced red hue.

I applied the solution with a brush, then wiped away the excess.  Tanned under UV for about 2 hours (no color change when I went up to three hours).

QUESTION: Should I apply more solution to the maple and tan further, or just bear the difference?  Any risk to applying more?  I plan to test on my samples to see if a second maple treatment looks more like the spruce sample.

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I would suggest soaking your spruce with regular water before applying the stain. Since you've already done it on this instrument, I'd give it a few days of tanning before trying anything else.

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I recently tried the same with sodium nitrite, 4% by mass. On a well tanned piece, a second coat makes almost no difference. I have not yet tried this on spruce but will post the results. 
I also want to try soaking various resins in this, to test for colour change.

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What I do for spruce is brush water with a damp brush then follow immediately with a (different) SN dampened brush.  Damp not loaded brush.  I do the end grain as the brush is starting to run dry.  I need to experiment w/ Jeffery's suggestion.  UV box for a day, then apply touch-up SN on any light spots if they occur.

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I also found that a second application has only a miniscule impact on the darkening. 

I did find that more time in the light box helps the maple tanning "catch up" to the spruce.

Applying a weaker solution to the top seems like a perfect solution!

Given the that a double application makes no material difference in tanning, the wet-then-apply approach seems like it is probably just a dilution effect. (So why not use a dilute solution in the first place?)  I will give this approach a try as well and see what happens.

Thank you all for your kind assistance.

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And, since all wood has slightly different chemistry, you probably want to use an offcut of exactly the wood you have to see how it reacts before experimenting on the instrument.

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Amen to using offcuts for testing!!!! During a build, my shop is littered with all of the little parts and bits that I save for just that purpose.

I can see that blotchiness could be an issue if you are using a more dilute solution - and prewetting would lessen the problem

 

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15 hours ago, JohnCockburn said:

It does.

Agree. I put the stuff on with a sponge and keep going back over again wet on wet until everything evens out. I also figure at least two applications and an extra on maple.  Most of the time I am making willow backed cellos so the only maple is the scrolls and sometimes ribs. I also use 3% not 4.

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Right. When chemically staining do not nuke the wood with high concentrations. Less is more because it is controllable. Excess oxidants can be hygroscopic (attract water) which means that in high humidity they reactivate and degrade the wood structure over time.

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1 hour ago, Michael_Molnar said:

Right. When chemically staining do not nuke the wood with high concentrations. Less is more because it is controllable. Excess oxidants can be hygroscopic (attract water) which means that in high humidity they reactivate and degrade the wood structure over time.

Well said.  We speak of this process as as "oxidation of the wood".  I think of it as a controlled burn.  Not always predictable or controllable as all burning is.

on we go,

Joe

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On 2/11/2020 at 2:40 PM, Shunyata said:

 

QUESTION: Should I apply more solution to the maple and tan further, or just bear the difference?  Any risk to applying more?  I plan to test on my samples to see if a second maple treatment looks more like the spruce sample.

Are you trying to get the maple more red like the spruce? Do you like the red color in the spruce?

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5 hours ago, joerobson said:

Well said.  We speak of this process as as "oxidation of the wood".  I think of it as a controlled burn.  Not always predictable or controllable as all burning is.

on we go,

Joe

Hi Joe,

More than a half century ago I saw an old gun stock maker scorch a newly made curly maple flint lock rifle stock he had made to darken it and bring out its figure.  I think I recall he used an old fashion blow torch and he quickly moved the flame back and forth over the wood in a direction parallel to the curls.

I remember seeing stocks that looked beautiful after he finished them (oil finish?).

 Funny how I can remember things from long ago and I can't find my car keys. 

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2 hours ago, Marty Kasprzyk said:

Hi Joe,

More than a half century ago I saw an old gun stock maker scorch a newly made curly maple flint lock rifle stock he had made to darken it and bring out its figure.  I think I recall he used an old fashion blow torch and he quickly moved the flame back and forth over the wood in a direction parallel to the curls.

I remember seeing stocks that looked beautiful after he finished them (oil finish?).

I don't recall ever seeing a gunstock finish which came anywhere close to the finishes on the most coveted violins. But each is an acquired taste, I suppose.

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No, I am not thrilled with the red color, although it seems to work very nicely under a madder finish.  I also find that different maple pieces (i.e. neck and body that came from different trees) do not act the same.  

I did find that even longer in the light box, 16 hours or so, made a big difference.

Lots to learn and I value the comments!

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12 hours ago, Shunyata said:

No, I am not thrilled with the red color, although it seems to work very nicely under a madder finish.  I also find that different maple pieces (i.e. neck and body that came from different trees) do not act the same.  

I did find that even longer in the light box, 16 hours or so, made a big difference.

Lots to learn and I value the comments!

yes, there is more to learn than you might think

10 hours ago, scordatura said:

Sodium Nitrite has less of  a pink color.

i've not found any difference in colour between KNO2 and NaNO2. And I've never had spruce go red :)

 

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21 minutes ago, JohnCockburn said:

yes, there is more to learn than you might think

i've not found any difference in colour between KNO2 and NaNO2. And I've never had spruce go red :)

 

I have seen the red tint he is talking about but it turns browner with time and light. Also can be modified slightly greyer by fuming a few hours with household ammonia.

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18 hours ago, Marty Kasprzyk said:

Hi Joe,

More than a half century ago I saw an old gun stock maker scorch a newly made curly maple flint lock rifle stock he had made to darken it and bring out its figure.  I think I recall he used an old fashion blow torch and he quickly moved the flame back and forth over the wood in a direction parallel to the curls.

I remember seeing stocks that looked beautiful after he finished them (oil finish?).

 Funny how I can remember things from long ago and I can't find my car keys. 

kills the chatoyance,  The worst muzzleloader finish I've seen was by a well known maker, he used some kind of tar mixture.  

Look under sofa cushions for the keys, that's usually where mine are.  

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On 2/15/2020 at 5:11 PM, David Burgess said:

I don't recall ever seeing a gunstock finish which came anywhere close to the finishes on the most coveted violins. But each is an acquired taste, I suppose.

Perhaps you might like coveted gunstocks.  

The Beretta firearms company in Brescia Italy has been in continuous operation since 1526.  I suspect that the gunstock varnishes used at that time were similar to what was used on early violins. They have a museum of ancient firearms but I am unaware if anybody has done an analyst of their varnishes.

I wouldn't be surprised that their beautiful high end modern shotguns still use similar varnish formulations.

https://www.beretta.com/en/world-of-beretta/private-museum/

Modern muzzle loader rifle makers try to duplicate traditional gunstock finishes and these seem similar to me to what violin makers use when they try to duplicate traditional violins.  Attached is one article describing this effort and it has a good list of varnish making references.

Muzzle Blasts Online,Vol. 5, No. 2; Traditional Varnishes As Applied to Gunstocking.pdf

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