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Berl Mendenhall

Cooking Colophony Down For Color, Low and Slow?

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That's good to know Michael.

And what about what goes on the spruce first, stains, ground varnish etc...?

Damn good question, Don. Spruce wicks up liquid stain like blotting paper. Well, almost. There are many ways to mitigate this. UV is a nice "stain", for instance. Some people control or limit the amount of liquid stain. 

 

To be frank, the answer to this is every maker's trade secret. You will not get many detailed answers. 

 

BTW, I was reminded by a friend how little pigment Stradivari put in his colored varnish. Brandmair & Greison noted that the red color is largely a property of the varnish medium. The pigments deepen or enhance the red.

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Hi Joe- apologize for incorrect classification- I think WW is water white gum rosin,  FF is dark wood rosin.   Referring to the function of the varnish contents, oil makes the film, resin imparts the hardness, and the way I use umber  is as a drier and colorant. If you were adding umber strictly as a drier you would  add something only around 0.02% umber to the amount of oil. Really tiny amount.

I'm surprised you didn't get any color to the oil when cooked with umber. The manganese in umber should have colored the oil gold brown from my experience. To body the oil to near string in an hour I suspect you should be using a temp around 500F Just a guess. With any rosin, the metals in umber will react with acidic factors of rosin, generating color and reducing the acidity. The long  lo temp cook method oxidizes the abietic acid, which darkens the rosin and also adds the color when spread  out in a film. Keep in mind these are different ways to make a rosin  varnish, long lo temp, short cook with metal. The colors in my finish are also caused by the dyes applied to the wood before varnishing.  fred

Hi Fred,

I had so much umber in the oil it was muddy looking so there was no way for me to see the color of the oil itself. I didn't check for string pulling in the oil itself as I really didn't know what I was doing or what to expect from the pre heating. I dont think I went much higher than 200°C. It is interesting to hear that is a possibility of adding color as well.

 

JoeHave you read Tad Spurgeon's information on oils?

I will have a look, thanks. I seem to recall the thread :)

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Damn good question, Don. Spruce wicks up liquid stain like blotting paper. Well, almost. There are many ways to mitigate this. UV is a nice "stain", for instance. Some people control or limit the amount of liquid stain.

To be frank, the answer to this is every maker's trade secret. You will not get many detailed answers.

BTW, I was reminded by a friend how little pigment Stradivari put in his colored varnish. Brandmair & Greison noted that the red color is largely a property of the varnish medium. The pigments deepen or enhance the red.

And here I thought the varnish was the secret! I was only just starting to suspect it was the ground. :D Thanks for the insight Michael ;)

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I will have a look, thanks. I seem to recall the thread :)

Have a serious look. The washing process is a lot of work but well worth the effort. You do not need to add driers to the oil once washed and preboiled. All instructions are there for the taking. I wouldn't add umber to the oil when bodying. I wouldn't add any pigment to the varnish cook either, for clarity sake. Sorry Fred. Just personal preference. The varnish can be colored afterward with the many different products out there. Joe sells some nice transparent colored varnish products and there are many others too. Like Neil Ertz's homemade madder pigment. There are some nice transparent artist pigments once you find them.

Good Luck cooking your next batch.

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Hi Emviolins,   I use just about any oil, since I get to temps that fry the mucilage foots that you wash out it doesn't make much difference, and it adds some color.  I think you miss the point that the color IS generated from the metals in the pigment reacting chemically with the rosin. The final varnish appears quite black, but when spread out on bare wood it starts gold and with coats winds up brown, which I desire. The varnish is very transparent, unlike coloring the varnish using insoluble pigments. I know its dumb re all the modern stuff available, but I prefer to use stuff that has a history. Happy making.  fred

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Hi Emviolins,   I use just about any oil, since I get to temps that fry the mucilage foots that you wash out it doesn't make much difference, and it adds some color.  I think you miss the point that the color IS generated from the metals in the pigment reacting chemically with the rosin. The final varnish appears quite black, but when spread out on bare wood it starts gold and with coats winds up brown, which I desire. The varnish is very transparent, unlike coloring the varnish using insoluble pigments. I know its dumb re all the modern stuff available, but I prefer to use stuff that has a history. Happy making.  fred

This is the last time I'll suggest reading the Spurgeon article but if you prefer to use stuff that has a history I think you will find the information to your liking. Since many of the methods for preparing the oil is taken from old manuscripts and recipies. Please know that I'm not knocking your method Fred. Whatever works and to each his own. Cheers.

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Have a serious look. The washing process is a lot of work but well worth the effort. You do not need to add driers to the oil once washed and preboiled. All instructions are there for the taking. I wouldn't add umber to the oil when bodying. I wouldn't add any pigment to the varnish cook either, for clarity sake. Sorry Fred. Just personal preference. The varnish can be colored afterward with the many different products out there. Joe sells some nice transparent colored varnish products and there are many others too. Like Neil Ertz's homemade madder pigment. There are some nice transparent artist pigments once you find them.Good Luck cooking your next batch.

Hi website seems to be related to refining linseed oil for making paints and not varnish. Seems to be a different animal. And what most people are saying here on MN, is adding pigments after a varnish has been cooked makes the varnish less transparent, which is what you want for oil paint.

Joe

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I just received a copy of the new Kremer Pigmente product catalog. It is much better in layout than the 2009 version that ran for 5 years.  :lol:

 

 

PS: Almost 120 pages with a 6 page index!

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post-25192-0-47124800-1403824573_thumb.jpg

 

This thread got me interested in trying it out, so I got a couple pounds of rosin and a small deep-fryer for $21 from Amazon.  I put in one pound of rosin and let it cook for 10 days at ~300F.  After the first day or two, it had thickened up and started forming a layer of "ice" on top, so I added 100g of walnut oil to keep it fluid and circulating.  I could have raised the temperature, but I didn't want to go any higher.  I also threw in 5g of a Michelman Zinc/Alizarin resin to get a bit more reddish color.

 

Today I added linseed oil until it was about the thickness I wanted, and that ended up at around 400g.  I have no idea how much of the original 454g rosin went into the air, but to me the viscosity is the important thing.  Maybe I can back-calculate at the end.  I'll let it simmer overnight and filter it in the morning.

 

I bought the cheapo deep fryer because it had an enclosure and a vented lid that seemed like it would avoid losing heat and costing $$ for electricity.  The outside surface does get quite warm, but I'm sure it's far more efficient than my hotplate and pot setup.  On the downside, it doesn't look that handy for pouring stuff out, and I noticed that the temperature setting gradually crept higher and higher.  The control knob actually moved from where it was set... probably a threaded adjuster with the bimetal switch tapping back and forth on it, but I won't know until I shut it down and take it apart.  As long as I checked a couple of times a day, it didn't get too far out.

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Color looks nice. I've been cooking some too in a crockpot. On high the temperature holds steady at 275 F. It's been cooking now for three days. I'm also refining 8 liters of linseed oil...

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. I was considering dissolving it in alcohol first so it may be filtered, but I was concerned that it may not dissolve some of the desired resin components.

Good thinking, Bill. We're pretty much (on the professional trade side) up to our asses (or ears) when it comes to resolving all the variables.

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Well well, looks like Don has finally cottoned on to what I was saying on my bass blog many months ago. Congratulations! Perhaps now that real scientist has come up with the goods, a few more might follow suit.

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Well well, looks like Don has finally cottoned on to what I was saying on my bass blog many months ago. Congratulations! Perhaps now that real scientist has come up with the goods, a few more might follow suit.

 

Hold on - Don's 'cooked' colour also had 5 g of Zn/alizarin.

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Don,

Clever idea about using a deep fryer. That color looks great. Please show us some varnished samples.

 

There's not much point in posting photos...

 

It looked very dark in the pot

A drop on foil looked dark ruby color

After oil was added, a drop looked nice orange/amber

In a thin coating, it was a decent light orange/amber

After it dried, it was basically clear.

 

Drat.

 

Next time I'll cut a hole in the lid to install my turpentine bubbler, and see if extra oxidation helps any (I'm presently oxidizing some turpentine with it, so it will be a while).  And I'll have to cook it until it looks horribly black.  And I'll have to just cook the resin, and later make up tiny test batches of varnish so I don't end up with another large quantity of nice, clear varnish.  I have plenty of that.

 

And I was right about the thermostat on my deep fryer... there's a threaded adjustment to put varying pressure on the bimetal switch, and I guess the light ticking back and forth was enough to slowly turn the knob hotter.  I'll just clamp it somehow.

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What kind of resin did you use and where did you buy it?

 

This stuff:

post-25192-0-43698300-1403964456_thumb.jpg

They sell on eBay.  It seems to be perfectly good stuff, as far as I can tell.

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Thanks. That is the same stuff I'm cooking at the moment. It's been cooking for 5 days and it is still clear when thinned out. I'm wondering if it is worth the cost of electricity to continue. I don't plan to add anything to darken it this way. Perhaps it really depends on cooking the right type of resin.

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I saved the woodsticks from my two batches (short time cooking ~45 min)

 

post-37356-0-63237300-1403983048_thumb.jpg

 

I'm going to make another batch these days and cook the colophony longer, maybe some hours. The problem is that it turns out different even with the same ingredients. The first one was more redish and the second batch was way too hard. Maybe a Little mastic would fix that?

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Hi Don, Carlobartolini is correct  that the resin you buy is critical, and seems to have nothing to do with what grade you buy.  I've only run the following test once, but I think it will indicate the quality of your rosin. Mix 1 part alcohol to two parts ammonia, grind up about tablespoon of your rosin, add the liquid to make a rosin slurry, if if goes dark brown it will retain color. If it is colorless (yellow) or weakly brown, I wouldn't use it. Why this happens I don't know.

All household ammonia you buy in markets today has a surfactant in it that is involved in the test, I think. Many years ago I added pure ammonia to rosin and developed a strong  color that is similar to when it is slo- cooked. Unfortunately  health and age collided and the pieces left aren't in too good a shape, so hopefully someone can make up some solution and see if it really works. It will save buying a bunch of rosin that is not useful.  fred

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If the goal here is to make colorant, and the Diamond G resin won't do,  then perhaps the right thing to do is add lime, sandarac, mastic and maybe some copal to make a clear varnish with what you have remaining.

 

I have 11 pounds of the Diamond G, a potato cooking kit and 1 extra pound.   I don't mind making a clear varnish out of it, right after I cook a few potatoes.   Mmmm... Potato Varnish!

 

I don't think I need to make a large batch of colorant anyway, so the question now is what to use for colorant making.   I am thinking of using a pint of Bickmore Pine Tar and a bag of batters rosin if it passes FredN's rosin test.  The pine tar is about like molasses so I expect that the rosin and tar will cook down and make about 3 oz of colorant, but that may be enough for 10 or so pounds of varnish.

 

Bob

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   I am thinking of using a pint of Bickmore Pine Tar and a bag of batters rosin if it passes FredN's rosin test.

Bob

I would avoid the pine tar. The creosote component will give you a variety of problems.

Joe

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I would avoid the pine tar. The creosote component will give you a variety of problems.

Joe

 

I appreciate the advice, I will pass on using it then.

 

Bob

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