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Varnish making - questions for the chemists


Jacob

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FWIW:

"Gums.  A group of non-crystalline, structureless materials, occurring widely in plants, composed mainly of carbon, hydrogen, and oxygen, and forming viscous solutions or mucilages, is given this general name.  Their chief characteristic is that they dissolve in water, forming a clear solution, or swell when they are soaked in water.  This differentiates them from resins which are sometimes misleadingly called by the same name.  Gums differ, also, from gelatins, glues, and proteins, which form similar mucilaginous solutions, in  that the latter are definitely nitrogenous bodies, while the gums contain practically no nitrogen.  They are insoluble in alcohol, do not melt but char on heating, and do not give off a nitrogenous odor."

 

Painting Materials, by Gettens & Stout (Dover republication of the edition of 1943)

 

"Gums are exuded or tapped saps from trees or shrubs and either dissolve in warm water or swell into a jellylike mass called a colloid solution."

 

The Painter's Handbook, by Gottsegen, 1993

 

The violin world has tended to borrow its finishing terminology more or less from the world of artist's materials, which at various times has received infusions of terminology from the sciences.  Science may have refined or even changed the meaning of terms since the last infusion.  That might or might not be an issue in the arts, or for us.  I suspect that we would do well to find out what the current position is in the sciences, given that violin research and varnish-making are both interacting with the sciences more and more these days.

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Andres ,to confuse matters further take Gum Arabic for instance. It can have a protein content of up to 3 % depending on the source of acacia tree. When burnt it can result in around 0.5 % nitrogen, which sounds small but considering up to 15% of the gum  is moisture/water   and up to 65% is volatile components it begins to sound  less  insignificant.

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Maybe this description helps;

Agricultural Marketing Service, USDA

http://www.gpo.gov/fdsys/pkg/CFR-2012-title7-vol3/pdf/CFR-2012-title7-vol3-sec160-8.pdf

§ 160.7 Gum spirits of turpentine.

The designation ‘‘gum spirits of tur- pentine’’ shall refer to the kind of spir- its of turpentine obtained by distilla- tion of the oleoresin (gum) from living trees, and commonly known prior to the passage of the act as gum spirits, gum turpentine, spirits of turpentine, or oil of turpentine.

§160.8 Steam distilled wood turpen- tine.

The designation ‘‘steam distilled wood turpentine’’ shall refer to the kind of spirits of turpentine obtained by steam distillation from the oleoresinous component of wood whether in the presence of the wood or after extraction from the wood, and commonly known prior to the passage of the act as wood turpentine, steam distilled turpentine, steam distilled wood turpentine, or S. D. wood turpen- tine.

§160.9 Destructively distilled wood turpentine.

The designation ‘‘destructively dis- tilled wood turpentine’’ shall refer to the kind of spirits of turpentine pre- pared from the distillate obtained in the destructive distillation (carbon- ization) of wood, and commonly known prior to the passage of the act as de- structively distilled wood turpentine or D.D. wood turpentine.

§ 160.10 Sulphate wood turpentine.

The designation ‘‘sulphate wood tur- pentine’’ shall refer to the kind of spir- its of turpentine prepared from the condensates that are recovered in the sulphate process of cooking wood pulp, and commonly known as sulphate tur- pentine or sulphate wood turpentine.

§ 160.11 Quality requirements.

The several standards for spirits of turpentine, as defined in §§160.8 to 160.10, inclusive, shall be deemed to mean the respective kinds of spirits of turpentine having properties that con- form with the standard specifications adopted therefor by the American Soci- ety for Testing Materials, contained in appendix A to this part.

§ 160.14

§160.12 Standard designations for rosin.

(a) Rosin within the meaning of the act and the provisions in this part shall be designated as ‘‘gum rosin,’’ ‘‘wood rosin,’’ or ‘‘tall oil rosin,’’ as the case may be.

(B) The designation ‘‘gum rosin’’ shall refer to the kind of rosin remain- ing after the distillation of gum spirits of turpentine from the oleoresin (gum) obtained from living pine trees.

© The designation ‘‘wood rosin’’ shall refer to the kind of rosin recov- ered after the distillation of the vola- tile oil from the oleoresin within or ex- tracted from pine wood by any suitable process, followed by any necessary fur- ther refinement.

(d) The designation ‘‘tall oil rosin’’ shall refer to the kind of rosin remain- ing after the removal of the fatty acids from tall oil by fractional distillation, and having the characteristic form and appearance and other physical and chemical properties normal for other kinds of rosin.

§ 160.13 Grade designations for rosin.

The grades of rosin shall be des- ignated, from highest to lowest, by the following letters, respectively: XC, XB, XA, X, WW, WG, N, M, K, I, H, G, F, E, D, B. In addition, the letters OP shall be used to designate the grade of opaque rosin, and the letters FF shall be used to designate the grade of nor- mal wood rosin: Provided, That the product recovered in the refining of wood rosin, that is darker in color than the standard for FF grade, and that contains rosin acids in lesser quantity than is normal for such rosin, shall be graded and designated as B wood resin.

[11 FR 14665, Dec. 27, 1946, as amended at 17 FR 221, Jan. 9, 1952; 33 FR 8722, June 14, 1968]

§ 160.14 Opaque rosin.

The term ‘‘opaque rosin’’ shall apply to the article resulting when rosin un- dergoes internal modification indicated by a turbid, clouded, or opaque appear- ance, that is, loss of transparency, brought about by the occlusion of moisture or the formation of an exces-

After reading this I have to wonder if the smelly turps we have been seeing in hardware stores the past few years is the sulphate wood turpentine.

In reference to William Fulton's comments about gum vs. steam distilled turpentine in his book, that Jacob mentioned, perhaps he was referring to these modern descriptions of the different kinds? I don't have his book , I am ordering it.

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Hi Andres,

 

Good point. Science has indeed refined some terminology. For instance, I have mentioned the shift from dichroism to dichromatism for varnishes. The fact is that no one has total control on terminology and its use. Moreover, all these things are evolving, which is a good thing. We just have to keep up to date with the current usage (and so should our dictionaries.)  :) 

 

Good to hear from you.

 

Mike

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Thanks Mike.

Fiddlecollector--The more I think about your terebinth comment the more intrigued I become.  Very interesting, and wouldn't that be ironic in the end.

Getting back to linseed oil:

-Linolenic acid:  In the material linked on the first page of this thread Mr. Spurgeon specifically points to linolenic acid as creating film faults.  Apparently the value of an aggressive washing process is that it reduces linolenic acid in particular.  It's worth noting though that at 36 to 55 percent, and reacting strongly to oxygen, linolenic acid is a big part of what makes linseed oil what it is.  Most other drying oils don't have anything like so much of it.

-'Acids', 'free acids', 'acidity'.  Vegetable oils are essentially 100% fatty acids, so it is important to know which ones in particular are causing problems and at what proportions, and which ones are affected by what types of refining and to what degree.  Also, linseed oil can apparently have more or less free acids--is this just a matter of how polymerized the oil is?  Is this what is meant by the 'acidity' of an oil?

-Mr. Spurgeon sort of implies that washing removes non-polymerizing acids (the saturated ones I presume)--it would be nice to see that confirmed, and also see some sort of confirmation that they serve no useful purpose.

As I was puzzling over these issues I came upon an intriguing discrepancy between the figures given for linolenic acid in 1943 and the present.  In Gettens and Stout the figure is 36.4 to 40.3%.  At Wikipedia it's 51.9 to 55.2%.  Of course this might just be a matter of the particular plants that were tested, or the methods used, but if these are average figures and something has changed, it would integrate with the idea that the oil we get is different from what it was in the past.

Incidentally, some time ago I found out that there are strains of food-grade flax plant (in use since the '90s) which were bred to have as low as 5 % linolenic acid.  I also found references to strains bred for higher linolenic acid content (I have heard of as high as 60%).
 

 

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http://www.specialchem4polymers.com/tds/piccolyte-s115/hercules-aqualon/14103/index.aspx

 

This is the resin one gets in the Fulton varnish.  Years ago,  I bought an 80lb bag for under $100,  from the Hercules Powder Co.  They made all kinds of pine-derived resins.  I tried a couple others and abandoned them.  But they may very well suit the varnish makers who like pine-derivations.  I recall that the literature claimed that Piccolyte was used in chewing gum because of its low melting point. 

 

There is a line to click on:  "View all Ashland products."

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http://www.specialchem4polymers.com/tds/piccolyte-s115/hercules-aqualon/14103/index.aspx

 

This is the resin one gets in the Fulton varnish.  Years ago,  I bought an 80lb bag for under $100,  from the Hercules Powder Co.  They made all kinds of pine-derived resins.  I tried a couple others and abandoned them.  But they may very well suit the varnish makers who like pine-derivations.  I recall that the literature claimed that Piccolyte was used in chewing gum because of its low melting point. 

 

There is a line to click on:  "View all Ashland products."

 

John,

What is the melting point of this resin?

Thanks,

Joe

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John,

What is the melting point of this resin?

Thanks,

Joe

They sell a biterpene resin.  This is one form of Piccolyte,  maybe all of them.. Piccolyte has several varieties and I did not look them up.  It is pretty low,  so it is like mastic a bit,  except without the entrained essential oils.  You know the root of the word "mastic" I am sure.  They also make ester gum,  three abietic acids on a 3-carbon chain.  (esterfied with glycerol). 

 

Also one with four rosins on a single carbon,  analogous to methane.  The 4-alcohol is called  Penta-erythritol.  The OH comes off and the acid COOH is somehow combined into another ester.

 

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

 

The larger the molecule,  the higher the melting point.   Some of these resins have found their way into adhesives and various types of paper size.   Ester gum varnish,  when made years ago,  was considered a cheap varnish.  The resin using pentaerythritol is said by Wikipedia to be useful.

 

It is one reason I use modern materials.  That does not mean I will not eventually try to go back.   I suspect tree exudate varnishes because one has an infinite choice,  if that is what the oldsters used.  For example,  the terebinth tree.  I understand that it has been almost wiped out.  Terpenes etc,  are extremely plausible,  but which ones?  While everyone worries about small details in the linseed oil,  the terpenes are less discussed.

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  They also make ester gum,  three abietic acids on a 3-carbon chain.  (esterfied with glycerol). 

 

Also one with four rosins on a single carbon,  analogous to methane.  The 4-alcohol is called  Penta-erythritol.  The OH comes off and the acid COOH is somehow combined into another ester.

 

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

 

.

 

This is not technical enough for me.... :(

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This is not technical enough for me.... :(

I am sorry,  I never had chemistry courses.  But in general,  these resins are a lot like oils or fats. 

 

Fats are tryglycerides,  three fatty acids connected to a 3-carbon chain.  It is as if  they were acids combining with a base (Glycerin, a triple alcohol with three OH's).  Making soap removes the fatty acids from an ordinary fat with lye**.  You get sodium or potassium fatty acid soap  (in water) and glycerin as a byproduct.  I recall that my mother used to sell bacon grease to the local butcher.  All yous guys have great grandmothers (or previous) that may have made their own soap. 

 

Today my wife needs 25 bottles of similar stuff to take a bath.  And the tiny bases of the bottles make them all fall over if they are bumped.  I use a bar of soap for everything,  including shampoo.  Selling soap is a grand tradition,  (soap operas).

 

Now instead of fatty acids,  visualize the rosin (abietic acid) reacted with an alcohol with more than a couple of OH.  That is all it is.  An organic acid and organic base.  Alkyds get the name from  "alcohol - acid."  It is cheap and easy.  I think to do it you need some kind of intermediate step or perhaps a catalyst.

 

** An oil is a liquid fat.  Saturated fatty acids (few double bonds) make solid fats,  the extra double bonds in the fatty acids (linoleic and linolenic acids)  make for liquid fats.

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Johnmasters,

I am still not clear on the melting point of these resins...or at least the one you find useful.

thanks,

Joe

I don't use them.  I tried them and had to buy an 80-lb bag of each one to do so.  I threw them out years ago. 

 

BUT:    Anyone who wants to make colophony varnishes (or Fulton's poly-terpene varnish)  might do better with one of these better rosin-derived resins.   It may be that some plants have sap that is not exactly like pine sap.  Who knows?  Melting points range from 100 degrees C to maybe 150 or so.  There are a hell of a lot of terpene-related things out there.

 

The ACE spar varnish is an alkyd with phenol  plus linseed oil. Other alkyds use various seed oils and various poly-alcohols. So I  I don't consider it much different than a natural resin or other rosin-derived varnish.  So I use it,  in an emulsion carrier method.  If it were too hard,  I would add a little tung oil.  In general,  it would be a good idea to add 20% of the total oil as tung,  when the melt is cooling.  (Tung does not need to be heat bodied.  In fact,  it changes to a gelatenous mess if overheated.  One gets an isomer which gels.  See Wikipedia.)

 

Wikipedia generally can answer any question one has about this sort of thing.  And I don't like the idea of rosin or colophony in a varnish because its free acid radicals probably are bad as it ages.  Adding lime to the melt will make limed rosin.  This is just calcium rosinate.  It used to be used in cheaper varnishes,  just like ester gum (rosin reacted and made neutral with glycerin)

 

Limed oil using virgin oil will neutralize free fatty acids.  Those are calcium soaps of fatty acids.  They will take alizarin color.  Generally,  the metal-fatty-acid soaps will take a lot more alizarin than the metal rosinates.  Michelman stopped too soon.  He wanted to dry the soaps as he did the rosinates.  But it is not necessary.  The soaps can be cleared of water with solvent extraction.  I am sorry to blow your cover,  Joe,  but this method essentially makes varnishes similar to your own.  I usually have a colored soap with some varnish.  They dry well.  Metals are aluminum,  calcium,  iron,  magnesium,  any of the light metals.

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Johnmasters,

No doubt that this is an effective method for isolating alizarin based color for varnish making.  It is not, however, related to the method I use to create the color varnishes and color concentrate varnishes.

Thanks for the info on the terpene resins as I wanted to test this against what I made years back.

Joe

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No doubt that this is an effective method for isolating alizarin based color for varnish making.  It is not, however, related to the method I use to create the color varnishes and color concentrate varnishes.

 

 

Joe, could you give us a few pointers as to how you do it ? I'm thinking of creating a web site with all known violin varnish recipes. :)

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Joe, could you give us a few pointers as to how you do it ? I'm thinking of creating a web site with all known violin varnish recipes. :)

What I know of Joe's recipe is that he uses onion , guanciale, bucatini. smoked dried peppers, and garden's tomatoes. :)

 

And I agree with Adam. :)

Edited by carlobartolini
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Just for fun I heated 2 or 3 ml of lemon juice until I get an almost black paste that turns a nice brown in thin layer (that was because of the well know secret ink trick and I learnt that citric acid gives this colour). I wonder what would happen if some juice was added at the end of varnish cooking.

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Johnmasters,

No doubt that this is an effective method for isolating alizarin based color for varnish making.  It is not, however, related to the method I use to create the color varnishes and color concentrate varnishes.

Thanks for the info on the terpene resins as I wanted to test this against what I made years back.

Joe

Not related ?  In no way?  If you have metals,  it is related.  Somewhere along the line you are getting free fatty acids.  Otherwise, you would have to attach the alizarin at a double bond somewhere.  It seems to me that energy considerations make this unlikely.  Your method may be different,  but the end result is almost certainly a metalic soap-alizarin complex.  I know where I end up.  Do YOU?  sketch a molecule for me, scan it and post the jpg.

 

You may go through a process with wood ashes.  Just buy lye.  I know you have a proprietary process and it is not cost-effective for the others to make their own.   And do you know that you do not have metal soaps ?

 

I don't care what the process is.  I went straight to the dyed metal soaps in two or three steps.  One problem everyone has is that they are thinking of Cremona.  They should forget Cremona,  even forget violin varnish.  Then go learn what the basics are.  These basics are pretty simple.  Anyone with a highschool education can understand it.  It will go even faster for a person who has read Michelmann.

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It's going to be a large site then... :)

 

We'll see. My guess is that makers will slowly drift towards simple, "green", linseed / rosin varnishes. One reason would be MATERIAL SAFETY. Both in the EU and the USA, paints or varnishes applied to toys ( violins...) must comply with incredibly stringent regulations. Certain new, mass produced, violin varnishes would not qualify. They contain toxic metals, carcinogens, etc. If I am to touch a violin to my neck and face for hours on end, then I'd like to know what EXACTLY is covered with. 

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