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Cooking Colophony Down For Color, Low and Slow?


Berl Mendenhall
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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

The Store, Hong Kong Market, in Houston, TX, covers a wide range, but has a bit of a Vietnamese overtone to it.  The block is also labeled with hand writing as Tong Huong with accents over all the vowels.   In small print the package says, "Caution no claims of medicinal qualities are made use solely to season and/or make tea."    In even smaller print it says. "Packed by Xin Chang Trading Company Fangcun District Guangzhou China."   at $5.99 for 16 oz it is not the most expensive resin you could buy.  It is likely to be from Pinus massoniana  but it could be from Pinus elliottii. 

 

In any case I have no plan for this to go in my tea.

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Trying unknown resins is looking for trouble unless you do that sort of thing for kicks. :)

Trying known resins is looking for trouble.  Trying unknown resins qualifies as full blown bonkers. :D

 

Here is the worst part about using known resins.   You carefully record all the qualities and details of the batch you made.  You wait years and the finish you carefully recorded remains deep, rich, bright and scratch resistant and tough.  It does not check or peel or blister or become tacky.  It ages wonderfully.  The sound from the instrument is loud, bright, glowing and resonate.  You now know that you have the ideal finish. 

 

Two of the suppliers are gone, a third changed ownership and the fellow that provided to the fourth supplier died and there was no one to take over from him.

 

Using unknown resins just speeds up the process of knowing you can never reproduce what you have done, while assuring that you will have trouble during the batch.  In a way unknown resins makes the process more predictable. :blink:

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From by brother who has worked for many years designing plants to distill and extract products from petroleum and wood...

 

At around 156C (313F) rosin becomes viscid and starts to expel water and turpentine oils (terpenes). Very flammable and with distinct odor. As you continue to heat it, different distillates are emitted that tend to be odorless.

 

By the time you reach about 276C (529F), it becomes completely fluid and will eventually stop emitting any more water or distillates. I think he said they stop when no more distillation product is detected.

 

The basic chemical composition changes which accounts for it darker color and glossier finish when solidified. Readily dissolves in a variety of organic fluids, but he seemed to think it did not dry by polymerization. The solvent evaporates and the cooked resin reforms to its basic molecular form.

 

Sounds like something that should not be done with an open flame or in an enclosed area. >grin<

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...

Tango, I couldn't tell you how many days, so far it must have been around 100 hours. Gonna keep cooking the other half of the rosin another 100 hours. "TO DEATH and BEYOND". 

 

Hi José and others

 

Please...

 

Anybody could inform me the average temperature that is called "low temperature?
Please... so so, I need to begin cooking a slow colofonia varnish and don´t know how to control by eye.
I ordered a -50 to +300 C thermometer.
I only know that it must melt and darken
 
Thanks for any help
Tango
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Hi José and others

 

Please...

 

Anybody could inform me the average temperature that is called "low temperature?
Please... so so, I need to begin cooking a slow colofonia varnish and don´t know how to control by eye.
I ordered a -50 to +300 C thermometer.
I only know that it must melt and darken
 
Thanks for any help
Tango

 

I received earlier this week a bag with 10 kgs of a variety of colophony I have used in the past. It is from Portugal, so I presume it is from a Pinus Pinaster. 

 

As we all do, I couldn't help myself and had to start up some rosin cooking for varnish. 

 

It is now in the pot, at 180C with little variation. 

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  • 2 months later...

This thread is getting old, but I thought I'd just wrap up my experiences here.

 

This is a batch of varnish I cooked up earlier, using the pale Diamond G rosin.

post-25192-0-53368400-1418596642_thumb.jpg

Lovely color, nicely dichromatic going from amber to red... but only when it's very thick.  It only has a slight amber tint in normal varnishing thickness, and might lose a bit when drying in the sun.

 

So I got some darker FF grade rosin from Woodfinishing Enterprises to try to push for more color.  Cooked the same way, the first batch of varnish only seemed to be marginally darker.

 

For these batches, I kept the temperature about as low as possible while still keeping the rosin fluid... ~150C to start, 175C after a couple of days, and after about a week it would require 200C to keep it fluid.  At that point, I'd make it into varnish.  

 

I wanted to see how much color I could get, so I went another day at 200C+ (a bit over 400F), stirring in the skin that formed a few times a day.  In making the next varnish, I put in a small amount of Japan Drier, as the previous varnishes took an extremely long time to dry.  It looked OK, a bit darker and a bit more opaque... but I noticed that it didn't want to go thru the filter, even though it was thinner than some of the prior varnishes.  There was some kind of goo precipitating out.  Even the stuff that DID go thru the filter continued to precipitate goo.  Fail.

 

I thought the drier might have been to blame, so I tried again, going a bit farther with the cook until even at 400F, the resin was extremely thick.  No drier this time, but the linseed oil didn't even consider combining with the thick goo, even after a lot of stirring at 400F.  Another fail.  And lots of fun to clean up.

 

Here's what the sample sticks for the last 2 cooks looked like, at 1 day intervals:

post-25192-0-33261000-1418596643_thumb.jpg

 

The bottom line for me at this point is that I don't see this avenue getting to the color intensity I'm looking for without added pigments.  Perhaps there may be some source of starting resin that works better, but I'm done experimenting along this line for a while.

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This thread is getting old, but I thought I'd just wrap up my experiences here.

 

This is a batch of varnish I cooked up earlier, using the pale Diamond G rosin.

attachicon.gifDiamond G 4.JPG

Lovely color, nicely dichromatic going from amber to red... but only when it's very thick.  It only has a slight amber tint in normal varnishing thickness, and might lose a bit when drying in the sun.

My experience with the Diamond G rosin was sort of similar to Dons...the final result of the low and slow cook resulted in a red rosin but in a thin layer it amounted to only an amber color. In a thicker coat it would be more red. But my goal and I think everyone elses goal is maximum color and less varnish.

If I recall from the original bass thread post I think Roger said he brushed on one or two thick coats and then wore it off...

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So I got some darker FF grade rosin from Woodfinishing Enterprises to try to push for more color.  Cooked the same way, the first batch of varnish only seemed to be marginally darker.

I have cooked this rosin after being given a recipe from another known maker here on MN a few years ago but only for 8 hours. It was then cooled and the next day made into a varnish. After seeing the thread on Joe Swenson's bench and the color he achieved from many more days of cooking I thought it would be good to go back and try this rosin again.

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For these batches, I kept the temperature about as low as possible while still keeping the rosin fluid... ~150C to start, 175C after a couple of days, and after about a week it would require 200C to keep it fluid.  At that point, I'd make it into varnish.  

 I wanted to see how much color I could get, so I went another day at 200C+ (a bit over 400F), stirring in the skin that formed a few times a day.  In making the next varnish, I put in a small amount of Japan Drier, as the previous varnishes took an extremely long time to dry.  It looked OK, a bit darker and a bit more opaque... but I noticed that it didn't want to go thru the filter, even though it was thinner than some of the prior varnishes.  There was some kind of goo precipitating out.  Even the stuff that DID go thru the filter continued to precipitate goo.  Fail.

 

I thought the drier might have been to blame, so I tried again, going a bit farther with the cook until even at 400F, the resin was extremely thick.  No drier this time, but the linseed oil didn't even consider combining with the thick goo, even after a lot of stirring at 400F.  Another fail.  And lots of fun to clean up.

In my experience a week was not long enough to cook the Diamond G rosin. It took at least 3 weeks to start to get some color and I cooked mine around 350F if I remember correctly. I haven't cooked the WFE FF grade rosin low and slow yet so I can't say anything about time on that rosin.

I did not experience any skinning over because I cooked a large quantity in a large crock pot with a lid cracked just enough to let the steam out. After the initial cooking I stored the rosin in a glass jar.

When I made my varnish with this rosin I did not add any solvent to the cook. I only thinnned with Windsor and Newton white spirit when the final varnish was filtered and cooled down.

I have never tried adding Japan Drier to a cook. Very strange results Don.

I made two batches of varnish with the Diamond G red rosin. The first batch I cooked the oil and rosin at 500-550F and it reaches a firm pill in less than 2 hours. The second batch I cooked at a much lower temp like Roger mentions in the bass thread, just hot enough to combine the oil and rosin, never reaching the stringing stage.

The results were the hotter cook had a very short open/tack time and dried much faster than the lower temp cook. After a week or so both varnishes were cured. So it proved to me that the stringing stage is not necessary but is a good way to gauge the drying properties.

As far as color goes the lower temp cook retained more red color. The hotter cook resulted in a browner varnish. Makes sense and my experience so far has been if you want to retain more color from a low and slow cooked rosin then you should cook at lower temps.

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Recently I have been buying resins from many different suppliers. My thinking is that the color might come from using the right kind of resin. A pale colored rosin I bought from Portugal that I cooked turned to a dark red in just 6 hours. I think that batch of rosin holds promise as well as some other rosins I'm testing now.

I have also found a source for raw Aleppo pine resin. I have not had time to experiment with this but I am anxious to do so. The appearance of the raw gum is much different than anything I've seen.

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Don / Joe Robson (and others with successful cooks)  Did you use Lime and how much?  I have been fairly casual about amount of lime I have used in my regular varish cooking but am thinking with the longer cook, maybe it is more important to have a good ratio.  I have enough varnish for instruments into next summer but all this talk on super long cooked resin has my interest.  I have never cooked varnish in the winter and wonder if (potential) cold snaps at night might effect things.   Any ideas.

 

-Peter

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my results where about the same. My last batch the resin was cooked to about 500 to 550f for about 6hrs. Nice deep ruby red color and reduced in volume by half, mixed with oil very well, very nice looking varnish...... won't dry...ever

Dwight

Can you say what kind/brand of resin and oil you used?

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A few more details on my various cooks...

 

For the first one (Diamond G resin) I kept the temperature low, 310 - 320F.  4.4% lime was added at initial melting, with resulting foaming for quite a while.  I also think it thickened up the rosin, but I can't be sure.  After 2 or 3 days, it was so thick that I thought it wouldn't be circulating, so I added some oil, and continued to thin the mixture occasionally for a few more days, about a week total.  The resulting resin (even with oil in it, the stuff solidified upon cooling) was about equivalent to Ernie's 3-week cook in color.  Nice, but just a pale amber when spread out.

 

For the last 2 batches, I used no lime, and used FF rosin.  Instead of holding a low temperature and thinning with oil, I continued to raise the temperature to keep things sludge-free, quitting when things got thick at 400F (about a week).  Mass loss measured 35 - 40% on these two batches (the previous cooks were not measured), so I can't imagine getting any more mass loss than that, unless there's a lot of volatile stuff in other type of resins.  

 

In the last cook, I used an aquarium aerator to bubble air thru the rosin, as some posts suspected oxidation to be a factor.

post-25192-0-93614800-1418658960_thumb.jpg

I didn't see anything particularly different in this batch regarding the development of color, so my conclusion is that the red reaction is mostly related to heat... long and cool seems to give about the same result as hot and fast, until it gets so hot that it burns into brown.  

 

Getting a brown color is not a problem.  We have plenty of naturally slow-cooked resins around (asphalt) for that, without cooking up more.  Red is the tough one to get, and as yet I don't see a strong enough red in my experience to be usable on its own.  Trying to push rosin to more mass loss or more intense red just seems to end up with a brownish mess for me.

 

 

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