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Berl Mendenhall

Cooking Colophony Down For Color, Low and Slow?

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So if long cooking is all about the color, it brings up the question from the other thread - To antique or not (or if you want your violins to be really dark)

 

Then maybe it's all about finding the "right" colored Colophony!?

 

I mean old violins were much lighter when they were new.

 

Well yes, that may be correct and I suspect that it was so, but can we really be sure about that?

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I mean old violins were much lighter when they were new.

Well yes, that may be correct and I suspect that it was so, but can we really be sure about that?

 

Why of course!  All those hide glue repairs add weight........... :lol::ph34r:

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I have a bit of a hidden agenda here...

If the bother of cooking down rosin for days is only to end up with mostly a terpene resin, then:

A - I don't need to do that, as I have a big stock of terpene resin on the shelf, and could just use that

B - I had extreme difficulty trying to make a varnish out of terpene resin... ended up as useless glop... so I might just give this idea a pass.

If your terpene varnish end up as glop,,It has probably been aerated for too long.

It would seem nice to run it till it is a nice dark color, but it doesn't work that way.

Three to four weeks is about the limit to aerate it and still have it mix with turps and or oil and not turn to goo or salt out.

Or if it is cooked to death it will ruin it, it does not seem to be as tough as sap.

It is so purified and distilled then polymerized,,, it is rather tender so to speak.

Don’t over aerate it or overcook it. Only cook it till it becomes brittle upon cooling. And you really don’t even have to do that, you can add polymerized turp to oil then cook it till it pulls a thread.

After it gets close then put the high heat to it for just a bit,(if you think it is absolutely necessary.)

Mix it with oil cook till it pulls a thread and your good to go.

If I were to add driers, I wouldn’t do it until it was in a varnish form, it seems that driers in the terpene before it is in a varnish form,sometimes renders it unable to mix with the oil as it should.

I have cooked it low and slow like sap for a long period and it completely ruined it.

It will dissolve in acetone, xylene, mek or something similar, but try to make a varnish out of it

or mix it with turps and it will turn to a useless goo or it will salt out into hard chunks.

But you still can use it,,,by itself mixed with acetone,,you’ve mentioned it before.

The turp you use to thin the terpene varnish needs to be aerated for a few days till it turns a light straw yellow to make it polar non-polar so it will mix properly.

And if you don’t like the exothermic reaction ,,it can be made without one.

(I’ve never seen one)

Use a 250 watt heat lamp and position it so that the turp is about 100c. while the turp is being aerated,,

(I use a laboratory flask in a large pan)

The peroxides will off gas as they are being formed and there will be no exothermic reaction when it is cooked later.

The trick with this stuff is to get it fully polymerized but not too much.

No funny business with this stuff,,or it won’t work.

I have ruined a bunch of it, and been successful with a bunch,The first batches were perfect,,later when I just HAD to know why? did I ruin it.

It is just too simple for a knothead like me, ,I have a real bad case of the what if’s.

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I mean old violins were much lighter when they were new.

 

When they were new, or justy light period?

I was thinking about this fact just last night.

One impression I virtually always get when handling really old violins, is that they are always light. (weight wise that is)

I have come, over time, to equate old and valuable, with light weight...?

 

Has anyone else noticed this, or is this simply a personal or individual type of belief I have adopted because of the relatively few really old violins I have held?

I do not think I have ever handled one that was a heavy type violin. Like modern violins usually are.

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Two days ago I got my electricity bill for the time that included my last cooking session. It was almost 1500 euros. I guess that tells us something about how long. 

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Two days ago I got my electricity bill for the time that included my last cooking session. It was almost 1500 euros. I guess that tells us something about how long. 

[Puts a cake of Hill's Dark in her mortar to pound up with the other resins and shakes her head sadly over the follies of Mankind] :P:lol:

My bill for the same period probably wouldn't buy a case of your favorite beer :)

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Two days ago I got my electricity bill for the time that included my last cooking session. It was almost 1500 euros. I guess that tells us something about how long. 

The polar bears will be swimming up your street next week.  :)

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Hi Evan, I'm  surprised your aerated turpentine didn't dissolve what you were making.  It is possible you are not aerating it long enough. Adding oxygen  transforms many of the elements in turp from hydrocarbons  to alcohols, which are very strong resin solvents. This stuff is strong enough to dissolve Fossil Copal resin and it is possible to utilize this to make a copal varnish without the required cracking at hi heat.

 

The reason you didn't have the so called exothermic reaction was because of the temp you  were keeping while making it. You didn't allow water to accumulate by keeping it at a heat near evaporation of water. If you want similar examples of the so called exothermic reaction, pour some water into a fry pan with oil and heat it, or add some water to turp and try to boil it.  Adding what are called Boiling Chips, or maybe crushed glass, will prevent the sudden force of steam trying to go through the repelling liquid above. fred 

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Fred, the exothermic reaction in polymerized turpentine is different from that. The reaction is such that the temperature will continue to rise after it is removed from the heat source, and the violent boiling and frothing can easily cause it to overflow the container. It's one of the more dangerous ways of making varnish.

 

Much of this can be avoided by prolonged cooking at well under 150 C (the reaction temperature), allowing most of the reactionary materials to cook out, before raising the temperature above 150 C. Even that can be risky, because the thermometer won't necessarily be measuring the hottest spot in the container. If even a tiny spot at the bottom of the pan near the heat source rises above 150, you've set it off.

 

Another method is to add small amounts. Put 10 cc in a container which is way too large, let it react and stabilize, then add the next 10cc, etc.

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Hi Evan, I'm  surprised your aerated turpentine didn't dissolve what you were making.  It is possible you are not aerating it long enough. Adding oxygen  transforms many of the elements in turp from hydrocarbons  to alcohols, which are very strong resin solvents. This stuff is strong enough to dissolve Fossil Copal resin and it is possible to utilize this to make a copal varnish without the required cracking at hi heat.

Hi Fred,

nice to her from you,,

The point that I was making is in reference to the point that Don had terpene that would not make varnish.

In doing deliberate experiments (Sam C. and I talked a lot about terpene varnish and did a few things to see what the boundaries of this substance was,,so to speak)I took gun turp and bubbled it for a long time

and it would not make varnish.It would turn a deep beautiful burgundy red brown, but would not mix with turp or oil,,,only acetone or something similar. It was like locked up with it self or something,,maybe it

needed to be ran like amber or something I don't know. At this point it REALLY stinks. After 3 to 4 weeks of aeration it makes the best varnish, according to the conditions that I was working in.

If it was aerated longer then the varnish wasn't so good,, a little longer and the varnish would have a tendency to wrinkle,,a little longer and a lot of debris would settle out of the varnish over time,,

a little longer and the turpene won't even mix with the oil at all.

I believe that the chemicals that produce the exothermic reaction are off gassed if the turp is aerated while heated a bit.

These are just some of the observations that I have made. I am no chemist and don't know why,

these are just observations.

After fearful warnings from others I made almost a gal. of linoleum,,that was interesting,

one moment a smoking pot of varnish,,just a few seconds later a pan of rubber,

The stainless stirring spoon stayed stuck in that pan of goo for years,,

I wasn't strong enough to pull it out.

I left it out in the weather just to watch it. I think it would last forever.

It was mixed with "Good" terpere resin, I was fairly sick.

By the way, at your suggestion I have some ferrous sulfate heptahydrate,,,

I wanted to try to use that for coloring,, will that work,,,

You might have to hold my hand and walk me through it,,

but I'm ready.

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I think it was the Florentine painter Cennino Cennini who talked about goose feathers for varnish cooking, but he may have been doing something else with them. Very nice book I seem to remember, but it has been a while since I waded though it. I think Dover reprinted it. (Cennino d'Andrea Cennini's 'Il Libro dell'Arte''). Yes! Just found it. Apparently still available from those people we love to hate 'Amazon'. 

The Craftsman's Handbook: "Il Libro dellArte": 

As for the Cremonese makers cooking their own varnish, this is highly unlikely. With the amount of wooden buildings in those ancient cities, varnish cooking was almost certainly restricted to outside the city walls. I have no idea where I heard this, (I think from Herr Fischer in Hamburg), but I believe that two women were killed outside the Hamburg city walls by a varnish explosion. Throughout Europe, professions and activities of all kinds were strongly controlled by guilds. In view of the dangers it is extremely unlikely that varnish making would have been carried out within the city walls of Cremona or by violin makers themselves.  

 

Not only that,  but according to a 1901 book on varnish making I found in a university chemistry library:

 

The best varnishes are produced in large pots of quite a few gallons.  This makes it easier to control cooling amongst other things.  The cooling recipes seemed important for the various chapters I read.  The book was concerned with commercial oil varnishes,  so they had various copals and various oils.  Stand oil of some kind was often used. And they wanted clear and colorless varnishes.  Turning yellow was a bad thing in general.

 

If the oldsters used such a varnish (but with colophony),  Such a large operation would certainly be done outside city limits. 

 

Nobody has discussed this idea of large recipes being a help.  I hope this helps someone making small batches.

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The old commercial oil varnish makers I talked to liked large batches for consistency of the end product. But I've achieved good consistency with small batches around 100 grams, when everything (including temperature) is done exactly the same way every time.

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Last nites pour,,,,

post-48078-0-87718900-1400010574_thumb.jpgpost-48078-0-22292500-1400010581_thumb.jpg

The worlds largest colophony parking garage,,,,

post-48078-0-12388200-1400010596_thumb.jpg

My 5 yr old said ,,"I take it that this is a piece of glass"

He's so cute,,

They were all very happy to see that the sticky nasty sap that we collected could be used for somthing good made them very happy,,especially now that it is not sticky anymore.

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Hi- I will try and respond in general to the last posts. Re an exothermic reaction- in fractional distillation, say you're running a bootleg still and you want tomake some really good stuff, so you carefully watch your temperatures, you know that methanol, the bad stuff distills off at a temp just below ethanol, so you dump this stuff and wait until the temp starts up (for each alc has its  specific  temp at which it boils and turns to a vapor) which indicates you're now distilling off ethanol, and the temp will stay constant until all the ethanol distills off and the temp then jumps up to tell you propyl alc is distilling off and you dump this. The same thing is happening in aerating turp, but you're getting  water below something it can't distill off when it gets to the temp it should happen. But steam keeps building below until it reaches a pressure that  violently forces it out. Also, I don't think the term polymerize is correct usage, for what I feel is happening is what you would expect when you bubble air through a hydrocarbon, which is a Condensation reaction where the final product is water.

 

This paper " Manufacture of Varnishes"  by J Wilson Neil 1833, Transaction Royal Society of Arts. 49: part 2. pp33-87. is probably the best insight to varnish making almost into Strad's time for Neil had been making varnish for over 30 years before he wrote the paper (ca1800), and his teacher had to have gotten his training in the late 1700's. The paper has great detail in constructing a varnish house, epuipment, and the myriad of varnishes made. I love his introductory statement- " Hitherto the art of varnish-making had been kept, in its details, as far as possible, a profound secret......."   The fact that rosin or any of its types are never mentioned  is interesting. It is great reading.

 

Evan, the green vitriol was for combining with soap to make an oil soluble dye. I tried to figure what you were making in your post but I gave up.  Can you tell what is terpene. Is it some kind of special turpentine. Also, what is gun turp. In reading your post it sounds very much like making a Fulton varnish. fred

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 in fractional distillation, say you're running a bootleg still and you want tomake some really good stuff, so you carefully watch your temperatures, you know that methanol, the bad stuff distills off at a temp just below ethanol, so you dump this stuff and wait until the temp starts up (for each alc has its  specific  temp at which it boils and turns to a vapor) which indicates you're now distilling off ethanol, and the temp will stay constant until all the ethanol distills off and the temp then jumps up to tell you propyl alc is distilling off and you dump this.

This is absolutely not true. It is an often-repeated myth. I have considerable experience with distillation, both with and without water being present (and both industrial solvents and moonshine). Take a few minutes with your "Handbook of Chemistry and Physics" and look up the table of boiling points for mixtures of ethanol and water. And even with a very good column still what you get off the top is only 96% ethanol because it boils at a lower temperature than 100% does.

 

David is correct. Sudden evolution of steam does not cause a temperature increase.

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Hi Fred,,

Sorry if I'm too vague,,

I am talking about Fulton varnish,,

aerating gum turp, to polymerize it and turn it into a terpene resin.

and if the turpentine is over aerated it will no longer make varnish,, something happens with the resin

that has been created out of the gum turpentine,,,,, if it is over done.

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Hi Captainhook- thanks for your response. I was hoping those with knowledge in fractional distillation would recognize this portion as a very generalized description of it and nothing more. Sounds like you can tell a few adventures in making the stuff.

My problem is that this process of making a resin by bubbling air through it is often ended with the statement of a " exothermic reaction." Those that were monitoring the temp stated it occurred  in the range of 300-350oF. Since you are a chemist you know that to obtain such a result you need some substances  chemically reacting. It cannot be heat of solution for there is nothing in this state. Nobody has mentioned what are those compounds. If someone comes up with them  and shows their reaction occurs in the temp range I'll certainly agree the exothermic result has a true origin.  

Your quote of David that steam does not increase temp is true, but that is not the issue. When the steam finally blows its way through the insoluble above it and  dissipates, temp starts going up for steam was utilizing heat to make steam which is not longer present  and the compounds begin boiling off  as their respective boiling points are met. That is my interpretation, and i'll have to stick to it until someone names the reacting chemicals. fred

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If all you want to do is darken the rosin, why not add some metal (iron, copper) shavings to the heated batch?  It should dramatically increase the rate of darkening.  Manufacturers of rosin go to great lengths to eliminate the presence of iron because their goal is to make it as light as possible.  There are some old patents on this.

 

~0.01% carbon black will do it too.

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If all you want to do is darken the rosin, why not add some metal (iron, copper) shavings to the heated batch?  It should dramatically increase the rate of darkening.  Manufacturers of rosin go to great lengths to eliminate the presence of iron because their goal is to make it as light as possible.  There are some old patents on this.

 

~0.01% carbon black will do it too.

The issue is controlling and stabilizing these ions. Over time some of these can change in unpredictable ways resulting in color and opacity changes. Varnish makers are trying not to make the varnish more black but stronger (deeper) in color. The colors are absorptive (CMYK color system) which means the varnish will look dark (black) in thick layers, but in thin layers their color shines through.

 

I will be giving a talk related to this topic at this fall's VMAAI in Tucson.

 

Mike

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Your quote of David that steam does not increase temp is true, but that is not the issue. When the steam finally blows its way through the insoluble above it and  dissipates, temp starts going up for steam was utilizing heat to make steam which is not longer present  and the compounds begin boiling off  as their respective boiling points are met. That is my interpretation, and i'll have to stick to it until someone names the reacting chemicals. fred

 

 

I'm familiar with water content turning to steam, having cooked motor oil to determine the water content. Totally different thing.

With the turpentine, once the reaction starts, the temperature continues to rise above the reaction initiation temperature with no further heat input (the reaction furnishes the heat) until the reaction is finished (or until you somehow cool it below the reaction temperature, as by putting the container in ice water). I don't know what the compounds are. There's quite a bit written on turpentine and turpentine products undergoing exothermic reactions though, if you do a search on it.

 

To the best of my knowledge, rosin (the distillation product) doesn't do this upon heating.

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Hi David, the only source of a bona fide reaction that I can imagine is release of peroxides, the method to transfer  oxygen into active compounds, and in the 300-350F range  there about 10 in turpentine. I can't imagine a sufficient amount of this stuff could be present to create such a prolonged reaction. Anyway, what happens  proceeds and accomplishes what needs to be done. fred

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Hi David, the only source of a bona fide reaction that I can imagine is release of peroxides, the method to transfer  oxygen into active compounds, and in the 300-350F range  there about 10 in turpentine. I can't imagine a sufficient amount of this stuff could be present to create such a prolonged reaction. Anyway, what happens  proceeds and accomplishes what needs to be done. fred

No need to imagine. You can try it for yourself. Please be careful!

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Hi David, the only source of a bona fide reaction that I can imagine is release of peroxides, the method to transfer  oxygen into active compounds, and in the 300-350F range  there about 10 in turpentine. I can't imagine a sufficient amount of this stuff could be present to create such a prolonged reaction. Anyway, what happens  proceeds and accomplishes what needs to be done. fred

The first violin maker that I knew and got me started was previously a chemical engineer at a nuclear laboratory. He said it was the forming of peroxides that created the exothermic reaction.

and If the turpentine was kept at 100c while it was being aerated the peroxides would be released as they formed, and there would be no exothermic reaction.

I know squat about chemistry,,and I have bubbled a lot of turp. and I have never seen the reaction,

but I have always heated it while I bubble it.

I have heard of a lot of other guys talk about the reaction that they get,,where the stuff starts cooking itself,,and it just keeps getting hotter and hotter on its own.

I have also been told that the thermometer will keep rising during the reaction.

Maybe someone else that has seen this can confirm it.

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There was a time when I was trying to make copal varnish using oxidized turp and experienced that reaction. I used boiling chips to minimize it which indicates its passage of something. Boiling chips are always used if odd mixtures are being heated.  Someone on Tobi also mentioned using a wide mouth container  considerably reduces the effect. fred

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