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JohnCockburn

Sodium Nitrite/Imprimatura Dorata?

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OK, I’ve read as much as I can find on MN about pre-varnish treatment to get some colour into the wood. It seems that the preferred method is UV treatment alone, but in my experience it can take up to 6 weeks to get a really nice colour. My problem is that I only have a very small workspace, which is fully occupied when I have my UV-box up and running. So, all work has to stop during tanning/varnishing.

To speed the process up, I’m thinking of going down either a. the sodium nitrite or b. the imprimatura dorata route. Obviously a) has the benefit of being much cheaper, but there seems to be some feeling that SN can cause deterioration of the wood in some way. However, in addition to ID being fearsomely expensive, I’m a bit reluctant to slop stuff all over my instruments when I don’t really know what it is.

Thoughts, anyone?

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At a 3 or 4% concentration the sodium nitrite is not very harsh. The thing about it is that the wood color will tend to "lighten up" a bit after you apply varnish on the treated wood. Factor that in to your assessment of how dark the wood needs to be before you apply your ground.

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Here's another perspective: Just finish the instrument and be done. I can't imagine any player giving more that one hoot about a sun tanned violin. :)

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Here's another perspective: Just finish the instrument and be done. I can't imagine any player giving more that one hoot about a sun tanned violin. :)

upnorth,

For some makers there is a practical reason for wanting to add some color to the wood. A bright white surface under the varnish reflects a lot of white light to the eye. If we are "fighting" this white reflection.

then more varnish is needed to provide sufficient color. More varnish is generally accepted to be bad for sound.

There are a variety of ways to defeat white reflection in the varnish...wood color is one of the most effective.

It is also absolutely necessary to a good antiqueing job. After all, if the instrument looks good to the player, then they pick it up and stick it under their chin....making them pick it up is a large part of the reason to do a nice varnish.

On we go,

Joe

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I can say "amen" to the necessity of wood color for a good antiquing job...The first one i did looked fairly correctly antiqued, but it was ALL done with varnish, tints, glazes, etc. When the first tiny scratches appeared, they were as white as correction fluid, by comparison.

After that I colored the wood with coffee, but I eventually decided I was not satisfied with that look, and moved on. But I do not intend to ever again NOT color the wood by some means, whether a colored sealer, ground, or whatever. If I lived someplace that had sunshine, I would suntan the wood, but I do not, so... I have a UV box, but have not tried UV-tanning yet...only used it for varnish-curing. Guess I will have to try it.

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I can say "amen" to the necessity of wood color for a good antiquing job...The first one i did looked fairly correctly antiqued, but it was ALL done with varnish, tints, glazes, etc. When the first tiny scratches appeared, they were as white as correction fluid, by comparison.

After that I colored the wood with coffee, but I eventually decided I was not satisfied with that look, and moved on. But I do not intend to ever again NOT color the wood by some means, whether a colored sealer, ground, or whatever. If I lived someplace that had sunshine, I would suntan the wood, but I do not, so... I have a UV box, but have not tried UV-tanning yet...only used it for varnish-curing. Guess I will have to try it.

COB3,

To coin a phrase...Is time on your side? Hanging an instrument in natural light will give good color...different from the UV induced color. But it takes time.

Joe

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To speed the process up, I’m thinking of going down either a. the sodium nitrite or b. the imprimatura dorata route. Obviously a) has the benefit of being much cheaper, but there seems to be some feeling that SN can cause deterioration of the wood in some way. However, in addition to ID being fearsomely expensive, I’m a bit reluctant to slop stuff all over my instruments when I don’t really know what it is.

Thoughts, anyone?

One option is to use a little calcium hydroxide. Apply it with a very watery consistancy with a rag. This will yellow the wood and once it dries you just have some calcium carbonate on your violin. If you use oil varnish or a spirit varnish consisting of mostly tree resins then the calcium carbonate won't be visible. Doesn't work so well if you seal with shellac.

Another option, use no chemicals but seal the violin with either orange shellac or garnet shellac dissolved in alcohol.

Third option, dissolve some highly caramelized sugar in water and apply that to the bare wood.

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I wonder if the colorant qualities of black walnut have been tried. (The last time I raised a question about dye materials, while claiming complete ignorance in the subject, I was nevertheless indignantly chided for making a terrible suggestion. I am not suggesting black walnuts, or anything for that matter. They sure seem to stain anything that touches them, so maybe...)

HS

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I wonder if the colorant qualities of black walnut have been tried. (The last time I raised a question about dye materials, while claiming complete ignorance in the subject, I was nevertheless indignantly chided for making a terrible suggestion. I am not suggesting black walnuts, or anything for that matter. They sure seem to stain anything that touches them, so maybe...)

HS

I think walnut husk pigment was popular to provide shading in some German commercial instruments of the last century-termed 'Nussbaum'

Doug

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I use tea and sodium nitrite, as I've mentioned here before. I think I could do it with just tea. Applying a heavily coloured varnish over a dark suface is much easier, as Joe mentioned.

This what I get, in general, in general there is more golden in it, but I just have this photo:

DSC00050.jpg

DSC00051.jpg

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"To speed the process up, I’m thinking of going down either a. the sodium nitrite or b. the imprimatura dorata route. Obviously a) has the benefit of being much cheaper, but there seems to be some feeling that SN can cause deterioration of the wood in some way. However, in addition to ID being fearsomely expensive, I’m a bit reluctant to slop stuff all over my instruments when I don’t really know what it is." Johncee

Hi John, I think the ID and the oldwoods primer are both containing nitrites with maybe some other things. I wouldn't consider them as more or less safe than using just nitrite. Oldwood gave me some free samples of their two part primer, here are the results of their product. I've tried ID previously, and they look and smell very similar. These examples have less of a burnt/fried look than what Manfio is showing, possibly the concentration of nitrite is less, or it's a more controlled product in some way.

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Dont be afraid to add some water soluble gum or very dilute casein to the nitrite ,it gives a more even colour than using nitrite alone.I suspect there is something like this in these commercial grounds to limit absorbtion into the end grain areas..

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Dont be afraid to add some water soluble gum or very dilute casein to the nitrite ,it gives a more even colour than using nitrite alone.I suspect there is something like this in these commercial grounds to limit absorbtion into the end grain areas..

Hm... good idea, what would you suggest, gum arabic?

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Hm... good idea, what would you suggest, gum arabic?

That should work,you still get the darkening effect its just that it stays more at the surface instead of soaking into the parts of the spruce top ,which give that dirty effect.A good example of soak in on a spruce top is the Messiah Hill copy on Tarisio.looks like they used something to darken the wood which unfortunately spoiled the top ,ive seen it on a few of their copy violins.Its also useful to seal the top first with something like Gum arabic letting it dry and then applying the nitrite or whatever.(you still get the darkening as the gum will dissolve slightly).Its good to practice with things first.Dichromate can work also if your careful,instead of nitrite.Also tannin applied first ,which is rather resinous and also prevents the nitrite from soaking in,but when using tannin you have to be careful with the concentration of nitrite.Casein is good for sealing backs but it has a tendency sometimes to produce small hairline cracks in tops and ribs.

hill top

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Interesting fiddlecollector.... now I know why in their book on Stradivari the Hills call spruce a "treacherous wood"!!!

I've noticed also that in places where the wood is stained by glue the sodium nitrite is more effective. Would you reccomend a concentration of the gum?

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Interesting fiddlecollector.... now I know why in their book on Stradivari the Hills call spruce a "treacherous wood"!!!

I've noticed also that in places where the wood is stained by glue the sodium nitrite is more effective. Would you reccomend a concentration of the gum?

Ive never really measured out casein or gum ,just make it very dilute with casein and like very thin glue with anything else,so that it doesnt really leave any noticable film on the surface.I tend to put a sealing coat all over ,and an extra coat in dark areas seen in the Hill photo.I then put nitrite mixed with the same gum solution all over and then stick it under UV to develope the colour.Its very similar to some photography techniques like gum bichromate.The nitrite developes colour when exposed to UV light like dichromate does.Hide glue can also be used ,though i dont like it as a sealer.(hence you noticed a stronger effect where traces of glue remained)

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Since this post alludes to Magister products I think it is only fair to mention that they have been offering an emulsion primer for some time now which is aimed to enhance even application. I have not tried it but here it is (primer 3) http://www.classicalvarnish.com/Primers.html

Personally I think nitrites can tend to make the ground too yellow if used without due caution

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I read this earlier and when I was in the basement before dinner I mixed up an emulsion of linseed oil, cherry gum in water, alcohol dyed with the leftover steel wool from the aged turpentine I made, and a little bit of borax. It made a mix that looked like cappuccino. It isn't a perfect emulsion, it now has a lighter layer on top of a darker one, but it darkened some samples real nicely. I think the oil in it make it easier to apply without blotching. I've tried shellac before and you have to be real fast, or maybe spray it.

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Very nice, Joe.

My current ground is darker, but it seems to work OK. I probably have some application issues-- I seem to most frequently emulate the proverbial "bull in a china closet" approach. Probably need to learn a more delicate style of work. :-)

This is how mine look with just the ground...

backwithgroundcoat.jpg

Chet Bishop

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I read a post here a few weeks ago about making "yellow onion skin" dyes. I just boiled some dry yellow brown onion skins for about an hour... no mordant .. no salt .. no alum .. just onion skins. Here is the result. I am going to leave it in the sunlight for a few days to see how colorfast it is.

post-24376-1237038439_thumb.jpg

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Since this post alludes to Magister products I think it is only fair to mention that they have been offering an emulsion primer for some time now which is aimed to enhance even application. I have not tried it but here it is (primer 3) http://www.classicalvarnish.com/Primers.html

Personally I think nitrites can tend to make the ground too yellow if used without due caution

That looks interesting, Melvin, but the short shelf life puts me off. I'd really like to try some of the Magister primers/varnishes, but I find the range of stuff available so confusing I wouldn't know where to start. And incorrect choices could turn out to be a waste of rather a lot of money!

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Since this post alludes to Magister products I think it is only fair to mention that they have been offering an emulsion primer for some time now which is aimed to enhance even application. I have not tried it but here it is (primer 3) http://www.classicalvarnish.com/Primers.html

Personally I think nitrites can tend to make the ground too yellow if used without due caution

Melving,

I know, I am being really picky, but on the Magister website, they have "PH" instead of "pH". I don't think any chemist would make this mistake. I know.. I know, really picky. My real beef is I can't afford their stuff.

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