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Berl Mendenhall

Cooking Colophony Down For Color, Low and Slow?

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Sounds like what happens when cooking methamphetamine goes wrong.

I can't say I have much (any) expierience cooking methamphetamine, but the moral of the story is that when one has finished cooking varnish, one should just switch the hot plate off, and wait a couple of hours until it has cooled down before even going near it. Should one take the still hot pot of the hot plate, and put it down on, for instance, a cold wall, it can ignite. A big DON'T DO!

One can still see from the street names, that our predecessors cooked varnish outside of town. In Vienna, for instance „Auf der Schmelz“, where nowadays the University is, would have been a medow outside the city walls, just as every Austrian town has a Lederergasse (Tanners street) where leather was cured,on the outside of where the city wall was in the 18th C.

That Strad cooked his varnish in his back yard will only be from the Walt Disney version.

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That Strad cooked his varnish in his back yard will only be from the Walt Disney version.

Maybe, maybe not. Certainly, there would have been a large demand for varnish and paint, and it would have made sense to put these dedicated larger operations outside of town. But would a high-end violin maker have used these products, any more than an high-end artist would have used them to make a painting on canvas?

 

Let's suppose a Cremonese maker wanted to darken some pine resin. Why not put a small amount in a pot hung to one side of the fireplace,  go on with normal cooking activities, and check it for color every few days or so? When it's dark enough, add some oil, and get it hot enough to combine.  It doesn't need to be a big deal, or complicated, or particularly dangerous.

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Maybe, maybe not. Certainly, there would have been a large demand for varnish and paint, and it would have made sense to put these dedicated larger operations outside of town. But would a high-end violin maker have used these products, any more than an high-end artist would have used them to make a painting on canvas?

 

Let's suppose a Cremonese maker wanted to darken some pine resin. Why not put a small amount in a pot hung to one side of the fireplace,  go on with normal cooking activities, and check it for color every few days or so? When it's dark enough, add some oil, and get it hot enough to combine.  It doesn't need to be a big deal, or complicated, or particularly dangerous.

David

Given that scenario would you consider that type of varnish an acceptable coating? I mean combining the oil and resin without the need for high temperature?

-No trip wires...

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David

Given that scenario would you consider that type of varnish an acceptable coating? I mean combining the oil and resin without the need for high temperature?

 

How hot do you think it needs to get?

Going over 250 C usually produces a varnish which self-levels better (and that's easily attainable in a fireplace), but Stradivi's varnish doesn't appear to have self-leveled very well.

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That Strad cooked his varnish in his back yard will only be from the Walt Disney version.

I really do not know either way. However, there seems to be a bunch here on MN that do make it in their backyard.

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Going over 250 C usually produces a varnish which self-levels better (and that's easily attainable in a fireplace), but Stradivi's varnish doesn't appear to have self-leveled very well.

 

 

I really do not know either way. However, there seems to be a bunch here on MN that do make it in their backyard.

A shame that Strad couldn't get David to make him a Batch of decent varnish, isn't it :rolleyes:

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How hot do you think it needs to get?

Going over 250 C usually produces a varnish which self-levels better (and that's easily attainable in a fireplace), but Stradivi's varnish doesn't appear to have self-leveled very well.

Thanks that helps.

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I've made it in my back yard at least a dozen times. I've never had a problem. I agree with David, if you're careful and scared of it, you shouldn't have a problem. There have been plenty of people who have no business making varnish to begin with, or cooking in a oil fryer for that matter.

My question is, how does anyone know where or if Strad cooked varnish? Those people served long apprenticeships with long hours. I doubt they just sharpened tools and carried out trash. I think they learned things like varnish making.

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The impression I get from reading about the industry in those times is that most trades were  controlled within guilds, similar to  modern employee unions. If an instrument maker was producing their own varnish they would be intruding onto the turf of the paint and varnish makers.

 

As I mentioned, this is just the impression I have arrived at. How strictly these guilds were enforced, I can't offer comment.

 

The other point is I think most instrument makers were busy doing that, building instruments. I don't think they had time to be out harvesting wood, cutting billets, gathering materials or making varnish, especially if a commercially made product was readily available to them. Some things just don't change over time.

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My question is, how does anyone know where or if Strad cooked varnish? Those people served long apprenticeships with long hours. I doubt they just sharpened tools and carried out trash. I think they learned things like varnish making.

Who knows? Maybe the Monks across the street made the varnish, and that's why there was this concentration of violin makers next to the  Basilica of San Domenico.

 

That's about as good as any other theory....

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From the various posts it seems there are two methods used for making rosin varnish, one is to keep it at a rolling melt for days of cook and another way using temperatures in the 5-600oF range. In the long days of cook method there is no mention of the container used which could be a source of color, but I  believe the darkening is due to oxidation. Literature on the chemistry of rosin mentions that long exposure to air, rosin darkens, the melting point goes up and the acidity is reduced. It seems the long cook is needed to generate the maximum darkening by the long exposure of rosin at the interface of the container with air. Probably a way to prove this is to put a lid on the container preventing air contact, or someone might have already done this and could comment if a change were noted. Essentially, because of the low temperature, abietic acid, a mixture of related resins, are  not chemically altered as in the high temp method. I only mention abietic acid for I think it is the main constituent of the varnish, but there are also many other compounds present that could be the source of color and film when altered with heat.

The method of going to temps of 5-600F is what I use, but my coloring comes from using a metal to form a resinate. I wish someone who uses these  hi temps and no metal could describe their process in some detail as to where they think what forms the color. Gum or wood rosin is acidic so adding metals like iron or manganese found in the painting pigment Umber will result in a brown/reddish tint color. I use Burnt Umber because the amount of manganese is reduced and iron is increased. I'm still learning so sometimes I start with only rosin and umber, or mix resin, oil and umber together. Rosin and a drying oil react chemically in an acid interchange, but it seems It only occurs at temps above around 500F. At the start of a hi temp cook, at around 300F, what are called rosin spirits cook off and there is a weak pleasant  incense odor with dark rosin. As the temp is increased to around 400F, the incense odor has some bite to it due to acid fractions breaking off the abietic acids, and as the temp goes up, the abietic acids are converted to pyroabietic acids from destructive heating. This is the acrid exhaust that really bites. I think as long as you stay at 5-600F this keeps happening. Cooking under 500F considerably reduces this, but a cook will take around an hour, almost double. I use as indicators for the end of a cook the reduction of surface foam in spite of  an increasing temperature, or being able to pull a 10 inch string. I recently tried Kremer Stand Oil and it should be beneficial, for the long cook at hi temp is really just to get the oil into a drying condition when spread in a film, and Stand Oil is already heat bodied, reducing this step in the process. Still trying to get where I feel I know what is going on.  fred

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Fred, I've made stand oil varnish. It's what I'm using now. It seems to pull a long string quicker than regular oil ( when cooking with resin ). I like everything about it EXCEPT it's drying. It takes a long time to dry. I use driers in it or it would take forever. You can't just put it in the sun like regular linseed oil. It will dry on the top but not underneath. I believe Joe Robson said it dries from the top down. I don't put it in the sun until it's dried in a dark box for about 3 or 4 days. It levels nice and looks nice, has that deep oily look to it. Maybe I did something wrong while cooking to make it dry like this, I don't know for sure.

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I've made it in my back yard at least a dozen times. I've never had a problem. I agree with David, if you're careful and scared of it, you shouldn't have a problem. There have been plenty of people who have no business making varnish to begin with, or cooking in a oil fryer for that matter.

My question is, how does anyone know where or if Strad cooked varnish? Those people served long apprenticeships with long hours. I doubt they just sharpened tools and carried out trash. I think they learned things like varnish making.

FredN: There is quite a lot of mention of containers on my 'Making a double bass blog' and in other places. It might help you to read the relevant pages this info does not just come from me

Berl: In spite of the text that Jacob has kindly shown us, I seriously doubt that the Cremonese makers cooked their own varnishes. This is also unlikely to have been a part of their apprenticeship. His text is from 1706 in Markneukirchen. This is not Cremona, where until the Austrians took over Cremona and eventually closed them down in the 1720's (I think) the guilds were still very powerful. But who knows?

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The impression I get from reading about the industry in those times is that most trades were  controlled within guilds, similar to  modern employee unions. If an instrument maker was producing their own varnish they would be intruding onto the turf of the paint and varnish makers.

 

As I mentioned, this is just the impression I have arrived at. How strictly these guilds were enforced, I can't offer comment.

 

The other point is I think most instrument makers were busy doing that, building instruments. I don't think they had time to be out harvesting wood, cutting billets, gathering materials or making varnish, especially if a commercially made product was readily available to them. Some things just don't change over time.

Very interesting to read about the guilds. It's very much like modern day trade unions. Interesting connection there.

http://en.wikipedia.org/wiki/Guilds

http://en.wikipedia.org/wiki/Guilds

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FredN: There is quite a lot of mention of containers on my 'Making a double bass blog' and in other places. It might help you to read the relevant pages this info does not just come from me

Berl: In spite of the text that Jacob has kindly shown us, I seriously doubt that the Cremonese makers cooked their own varnishes. This is also unlikely to have been a part of their apprenticeship. His text is from 1706 in Markneukirchen. This is not Cremona, where until the Austrians took over Cremona and eventually closed them down in the 1720's (I think) the guilds were still very powerful.  

Why should the Austrians have shut anything down??? What makes you think that?

I agree that Markneukirchen and Cremona are different places, but the interesting thing about the Stadt chronic of 1706 is that it shows that a cooked oil varnish was standard across a wide geography at the time, and not a “secret”(that Mr Reichel cooked his own himself quite by the way)

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Hi Berl (post 62)- Do you cook in the driers you are using. Stand oil is deceptive, it will let you pull a 12" string and never dry! Present commercial driers are cobalt and manganese, cobalt is a surface  drier, creating a skin as Joe mentioned, that is why they add manganese. I'd buy a tube of burnt umber which consists of manganese and iron both driers, and squeeze in a half inch,  and it will also add some color. To determine if you are adding drier in your system, add umber to oil only and heat until you see a color change which will indicate something has been incorporated. fred

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Fred, do the manganese and iron become inert once the film is dry, or is there the possibility that they will continue to react, changing the varnish color or something else?

There are stories of iron causing rosin varnishes to turn black....

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Hi David - I wish I knew. After the varnish is made and stored, there is still a black sediment deposited on the bottom which I think is from further reactions creating insoluble.  The varnish seems to be the same in application and color, but I only have samples from last august. fred

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Hi 

Always I like to read posts from FredN 

I believe that adding a metal to resin is the right way. It gives color and it's desiccant (polymerization catalyst). 

 

I'm afraid that when cooked at high temperatures, more than 280 C, all color will be brown. When cooking low color temperature will be different. I read that the red Fe2O3 is stable up to 160 C. 

 

Do you have any info what colors make these metal salts or oxides? 

 

Fe2O3 ----- red, brown? 

Allum (KAl (SO4) 2 · 12H2O) --- orange? 

Lime (Ca (OH) 2) ----- lower acidity 

ZnSO4 - I was hoping for red 

MnSO4. ? 

  FeSO4 - green vitriol? 

CuSO4 - bluestone? 

 

 

Question for Fred: In what form you are adding metals, lime in resin? As a solution or as a powder. When I put powder - lots of foam. I also make a clot, it looks like a sea sponge - fibrous. 

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An old-fashioned lead/manganese siccative:

 

http://www.jamescgroves.com/courtrai.htm

 

Works well, but the time-frame of my experience is limited.

Some good stuff there.

 

From Janito's link"

"Darkening is associated to both these metals (and copper, too). There is good reason for this association. Either lead or manganese (or copper) when cooked into oil will cause that oil to darken -- even blacken if heated enough. But here is the surprising thing: though the resulting cooked oil is certainly darkened by the metals, as long as it is not burned, there is no actual carbonization ; and the darkening is, instead, a fugitive coloration, i.e., not fast to light. The result being, the darkness 'goes away'-- and often this happens quickly and upon simple drying."

 

Yes yes yes. I have never used any heat-colored resin, with or without metals, which didn't lighten significantly upon drying under UV. It makes it pretty hard to know when you're done.

 

"The fact is, if your work is fine after a month, then it shall likely be fine after a year. If fine after a year, it shall likely remain fine for five. And if fine for five years, well, things look pretty good & you've done your job well."

 

No, a thousand times no. A month or a year doesn't necessarily tell you squat, it you're looking for much longer-term properties. I've had radical changes in some of my varnishes which didn't occur until 5 or 10 or 15 years later, or the equivalent in accelerated age testing.

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Fred, do the manganese and iron become inert once the film is dry, or is there the possibility that they will continue to react, changing the varnish color or something else?

There are stories of iron causing rosin varnishes to turn black....

I just a had a fiddle back in the shop, something I made about 4 years ago. I had made this dark rosin varnish, cooked with a rather generous the  amount of iron oxide in it, just varnish kind of job, no pigments added. 

 

It looked ok back then, not that I was pleased, but good enough for a folk player :P , it looks way darker now, Great colour, definitely more transparent.

 

 

"For the Power of Greyskull", I wished they looked like that every time I varnish a violin! Is it stable now? I'll know in a few years time, I am 33 years old, so I can wait. Definitely not sure I will do the iron oxide trick again, as I can get the rosin to colour dark enough with just heat and not having a metal reacting with it to colour makes me more confortable about long term stability.

 

Still, I have plenty of that varnish left... hahahahahah. Enough for at least 30 fiddles. 

 

my two penies worth

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I just a had a fiddle back in the shop, something I made about 4 years ago. I had made this dark rosin varnish, cooked with a rather generous the  amount of iron oxide in it, just varnish kind of job, no pigments added. 

 

It looked ok back then, not that I was pleased, but good enough for a folk player :P , it looks way darker now, Great colour, definitely more transparent.

 

 

"For the Power of Greyskull", I wished they looked like that every time I varnish a violin! Is it stable now? I'll know in a few years time, I am 33 years old, so I can wait. Definitely not sure I will do the iron oxide trick again, as I can get the rosin to colour dark enough with just heat and not having a metal reacting with it to colour makes me more confortable about long term stability.

 

Still, I have plenty of that varnish left... hahahahahah. Enough for at least 30 fiddles. 

 

my two penies worth

 

I don't wish to alarm you, but the major problem with adding iron oxide, or even cooking in an iron pot, is that you never know when it will stop getting darker. Some German fiddles have actually turned black.

 

David:  I don't know if you use the same method of cooking that I use, but I have had many samples, both in the dark and in my light box for at least 20 years. (Under UVB) Those in the light box do appear to have become a little more transparent. (I am not entirely sure about this)  However, none of the samples from the dark, or the UVB box, appear to have changed color in any way. They have certainly not faded. The same cannot be said for most of the variety of colors which were added to much the same varnishes. Almost without exception these have faded. (UVB is brutal) Some have disappeared entirely. (Best example being Dragons blood, both in shellac and oil varnish.)  

 

Metal salts of all kinds are generally more stable, but only if they are present as 'fixed' coulours. My main concern with them is that with only a few exceptions they are unatractive. 

 

Interestingly even batches from the same color source, taken at the same time, have changed at different rates depending on the way they were fix (or not) in the varnish. Madder, Penambuco, cochineal and seedlac precipitates and tinctures being the most obvious examples. 

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Why should the Austrians have shut anything down??? What makes you think that?

I agree that Markneukirchen and Cremona are different places, but the interesting thing about the Stadt chronic of 1706 is that it shows that a cooked oil varnish was standard across a wide geography at the time, and not a “secret”(that Mr Reichel cooked his own himself quite by the way)

 

Oh I agree entirely about the significance of this and I suspect it may even be the source of the "Hamburg" story, although I was always given to understand that this was 'Joachim Tielke' related. However, I had the information about the Austian governers of 'Northern Italy' from an impecable source. I cannot say more until I have asked, but apparently the Autrians tried systematically to destroy the guild systems of 'Northern Italy'. 

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