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Cooking Colophony Down For Color, Low and Slow?


Berl Mendenhall
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I tried hotter and longer, about two weeks, gradually increasing the temperature up to 400F to keep the stuff liquid as it thickened.  It did get much darker than the 1-week test, but still nearly colorless when diluted with oil and then applied thinly to wood.  It gives a nice golden natural wood color, if you just want that.

 

I show some other varnishes, over a ground, hopefully applied in about the same way and the same thickness, although there are differences in viscosity that make that difficult.   It is also a bit misleading in color, as some areas got more reflection or something; the last sample (reddish stock) is actually darker than the rosin varnish samples.

 

Color is also a little difficult to tell on wood, and easier to see on glass.  The iron rosinate I like very much, being a relatively strong orange/brown and perfectly transparent; the iron "M" varnish is a strong purple.  The stronger colors look a bit muddy on the wood due to slight roughness and pooling of color, but all of these varnishes are quite transparent.

 

Anyway, now I have a LOT of light golden rosin varnish, and I think I'd need to start with some darker rosin to get anywhere with this method.  Anyone need to varnish a boat?

 

post-25192-0-12304200-1410024033_thumb.jpg

 

 

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How many coats? And all on the same ground coat?

 

I see a lot of colour, so I would expect the  long cook one to do very well with a little mulled pigment.

 

Some superfine Oldies I have seen have pretty opaque varnish, while others only have worn ground left.

 

The key thing is that it should mostly chip off in about 20 years (I think that is what Charles Beare said about the Strad varnish).

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How many coats? And all on the same ground coat?

 

I see a lot of colour, so I would expect the  long cook one to do very well with a little mulled pigment.

 

The test strip was prepared with the ground coat (except for the very ends) and all varnishes are one coat, thin enough to avoid running when vertical.  I'm sure the rosin varnishes would be fine with a bit of pigment, but I think the idea was to get the color in the cooked resin, without the need for any added stuff.  With the pale rosin I started with, I don't think it can happen.

 

Hi Don, can you mention the iron used and the process of making. That sounds like an ideal varnish.  fred

It's based on Michelman's book.  The iron rosinate is as he described, although I used iron chloride instead of iron sulfate.  For the purple one with alizarin, I followed his recipe for "resin M", substituting iron chloride for the zinc chloride.  By the way... most of the iron resin M didn't incorporate into the oil, and got filtered out.

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Will you take a photo of your alizarin or madder pigment under uv, Don? I read that the purpurin flouresces yellow-red or violet.

My alizarin-based pigment does not seem to flouresce at all. I'm trying to figure out if my info is wrong or if my pigment is wrong. Ot I know. But I'm in the middle of a project with the alizarin...it'd help me to know. Or if anyone else could take a quick look at your alizarin under uv and say if you see anything interesting? Please & Thank you...

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My alizarin-based pigment does not seem to flouresce at all. I'm trying to figure out if my info is wrong or if my pigment is wrong. 

 

Mine doesn't either.  I tried the drying cabinet 350nm blacklights as well as a 254nm mineral lamp, and nothing lit up, including the high-alizarin zinc "resin M" that I have in solid chunk form.

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I just finished my first batch of colophony varnish and I thought I'd share. 

I wasn't getting any change in color or volume with the crock pot at around 350 F for a week

so I got a lab hot plate and cooked it for another week at 420 F.

Here it is after cooling..

coll.jpg

Holding it up to sunlight, you could see dark red peeking through. 

Here it is being ground..

collGrind.jpg

And the final product.. 

varnish1.jpg

It's very thick and looks jet black. When you tip it against the side of the jar you see dark red that turns golden as it thins out. 

 

varnish.jpg

I'll post some scrap tests soon.

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Purchased as alizarin. Thanks very much for checking yours, Don...There was a Strad article quite some time ago on how to make pigment from madder, by ..(?) a Washington State luthier....i should remember. It was a fantastic how-to. I'll have to pull that out. I love the color but if it's synthetic the RI probably won't be right imho.

It may be a misprint in my source or a misreading, and only the natural madder pigments have that strong flouresence. So is all alizarin-labelled product synthetic? ... and therefore contains no purpurin?

I have to go read some more. Ha...big surprise. I'll eventually make something. :)

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It's very thick and looks jet black. When you tip it against the side of the jar you see dark red that turns golden as it thins out. 

 

 

Looks identical to my result; in the very thin coatings I normally use, the golden gets very light.  Nice, but still not dark enough for the color I want.

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I just finished my first batch of colophony varnish and I thought I'd share. 

I wasn't getting any change in color or volume with the crock pot at around 350 F for a week

so I got a lab hot plate and cooked it for another week at 420 F.

Here it is after cooling..

 

Holding it up to sunlight, you could see dark red peeking through. 

Here it is being ground..

 

And the final product.. 

 

It's very thick and looks jet black. When you tip it against the side

 

I'll post some scrap tests soon.

Doormouse,

 

This looks very good to me. What material did you start with?  Rosin? Resin? Did I miss a post? What recipe are you following, please?

 

Thanks

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Nice.

 

What were your start and end weights?

I started with 200g rosin, not sure what the end weight was but it cooked down to less than half the volume. 

 

Doormouse,

 

This looks very good to me. What material did you start with?  Rosin? Resin? Did I miss a post? What recipe are you following, please?

 

Thanks

I was using the FF Grade Rosin that was recommended earlier in this thread. 

I'm trying out Mr. Hargraves varnishing process.

The consistency and color look about right but we'll see how it looks on wood. 

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I started with 200g rosin, not sure what the end weight was but it cooked down to less than half the volume. 

 

I was using the FF Grade Rosin that was recommended earlier in this thread. 

I'm trying out Mr. Hargraves varnishing process.

The consistency and color look about right but we'll see how it looks on wood. 

DoorMouse,

 

Thanks. I appreciate it. Will try when I get the chance.

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I started with 200g rosin, not sure what the end weight was but it cooked down to less than half the volume. 

 

 

What has not been resolved in this thread is whether the "cooking" simply leads to distillation of rosin components and concentration of what is left, or whether there is a chemical reaction that alters the colour of the residual resin.

 

These 2 situations could behave differently with respect to colour when the oil is added or a thin film is viewed on glass/wood.

 

--------------

I have collected distillates on an aluminium foli tent and it is pale greenish gold.

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What has not been resolved in this thread is whether the "cooking" simply leads to distillation of rosin components and concentration of what is left, or whether there is a chemical reaction that alters the colour of the residual resin.

 

These 2 situations could behave differently with respect to colour when the oil is added or a thin film is viewed on glass/wood.

 

--------------

I have collected distillates on an aluminium foli tent and it is pale greenish gold.

I see what you mean.  When I started the cook, although the colophony was already somewhat dark in color, there was no hint of red,

which leads me to believe there is something more going on than just reducing to a concentration.  

That's purely speculation though. 

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What has not been resolved in this thread is whether the "cooking" simply leads to distillation of rosin components and concentration of what is left, or whether there is a chemical reaction that alters the colour of the residual resin.

 

These 2 situations could behave differently with respect to colour when the oil is added or a thin film is viewed on glass/wood.

 

--------------

I have collected distillates on an aluminium foli tent and it is pale greenish gold.

I have not made up my mind, but today I lean to distillation. The evidence for me is trying to make some in a covered pot. I got a black goo much like tar that smelled horrible.
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As a matter of perspective, when you remove volatiles from a mass it is called reduction, when you extract the volatiles from a mass it is distillation.   

 

I don't think that reduction quite qualifies as the explanation of the rich red and gold qualities that evolve as the resins are cooked.  Certainly that is part of the process, but even when thinned to the same volume, the resin is still more than a few f-stops darker.  The reddening process here is more of a transformation than a reduction.  To use older terminology this process is specifically referred to as rubification.  The transformation of clear or white to red or purple.

 

It would be nice to call the resin cooking I do a science, but as typical of me, I recently saw a small brick of Colophonium on sale in an Oriental Grocery.  It was all by itself and the package spoke of years sitting with the other medicinal herbs and teas.  Despite the fact that I will never be able to obtain a similar block of resin and no knowledge as to it's true origin, I had to get it. 

From what I have read, there are two types of colophonium,  When you distill turpentine without the use of water the remaining solids are dark red.  When you distill turpentine with water the remaining solids are white.  The white was considered superior for making varnish but in this case I would have been delighted if this was the dark red.   Sadly, it is a very light whitish yellow. 

 

Sadly I am more of a rosin collector than a varnish maker.   Some day I may mix the odd partially identifiable resins collected together and try to make a batch of resin from them.  I am not sure which would be worse, a total failure or an absolute success that I have no chance at all of reproducing.

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Hi Bob- that is interesting about the block of rosin in a Chinese herbal store, I  wonder how they used it. The attachment from a text to my last post pretty much shows it is oxidation. Whether oxidation/reduction also occurs is not mentioned in the article, but there are  many other chemical reactions when rosin is heated to hi temps.  I believe it is necessary to go to hi heats to  cook off stuff that could create after tack. Let us know if you ever find out how the Chinese used it.  fred

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