Varnish making... and Lake making

[HoGo]

On 4/10/2025 at 1:05 AM, M Alpert said:

Yes. I tried Flavetta's recommendation, with Kremer Alizarin and zinc chloride, it worked very well! I am impressed with that.

I wonder if the color binds onto resin/oil or it creates suspension in the varnish? Does the color pigment setle over time? Can you see particles?

[LCF]

6 minutes ago, HoGo said:

I wonder if the color binds onto resin/oil or it creates suspension in the varnish? Does the color pigment setle over time? Can you see particles?

It isn't pigment ie not a lake. It's the dyestuff from the madder which dissolves in the varnish. Somehow. 

 

Hot liquid resin is itself a strong solvent.

[HoGo]

4 minutes ago, LCF said:

It isn't pigment ie not a lake. It's the dyestuff from the madder which dissolves in the varnish. Somehow.

Hot liquid resin is itself a strong solvent.

I though it is like that but what is the role of the zinc chloride or aluminium chloride in the reaction? Isn't there something like a rosinate forming within the hot varnish?

[LCF]

Just now, HoGo said:

I though it is like that but what is the role of the zinc chloride or aluminium chloride in the reaction? Isn't there something like a rosinate forming within the hot varnish?

Maybe but maybe the metal ions are ligands forming coordination complexes like with other metal complex dyes.

[LCF]

I had another thought about the espresso method - what if you put the powdered madder in a jar with just enough vinegar to moisten it, for a few days, before tamping it into the portafilter and making the madespresso? 

 

Also maybe @Davide Sora can confirm, I think he uses some iron sulphate in place of (some if?) the alum to get a darker lake. Which sulphate though, ferric or ferrous, or doesn't it matter?

[M Alpert]

3 hours ago, LCF said:

Maybe but maybe the metal ions are ligands forming coordination complexes like with other metal complex dyes.

@HoGo - sounds like @LCF has a better understanding of the chemistry than I do. I have imagined it is making a sort of zinc-alizarin rosinate, but I don't really know.

It's very transparent - it also clearly darkened and dissolved better with the zinc. There is a tiny bit of particulate matter that settled to the bottom, and the brushed on varnish is very nice, the best reddish varnish I have made yet.

It was Kremer Alizarin 94100 that worked. Also tried Alizarin carmine, and some other things that did not work well...

[Davide Sora]

9 hours ago, LCF said:

I had another thought about the espresso method - what if you put the powdered madder in a jar with just enough vinegar to moisten it, for a few days, before tamping it into the portafilter and making the madespresso? 

 

Also maybe @Davide Sora can confirm, I think he uses some iron sulphate in place of (some if?) the alum to get a darker lake. Which sulphate though, ferric or ferrous, or doesn't it matter?

Yes, I also do the roots fermentation with vinegar. I'm not a chemist, but I think it better predisposes the root to release the coloring principles by breaking down the glucose molecules. Regarding iron sulfate, I think it is ferrous sulfate, the one anciently called green vitriol, which consists of transparent green salt crystals. Used in place of alum, it produces a dark brown lake. When used in small amounts is useful for cutting down the excessively bright orange-red of lakes fixed on alum. The same purpose for which lamp black (carbon black or vine black) is used, but with a lower opacity of the pigment, which is, however, less transparent than the red lake fixed on alum (so use it sparingly). Madder fixed with zinc sulfate (white vitriol in ancient times) gives a redder lake with less tendency to orange than alum, although it is a somewhat bright and crude red. For anyone interested in pigment making, a must-read book is Jo Kirby's Natural Colorants. https://www.kremer-pigmente.com/en/shop/books-color-charts/992405-kirby-et-al-natural-colorants-for-dyeing-and-lake-pigments.html

[Davide Sora]

5 minutes ago, Davide Sora said:

Yes, I also do the roots fermentation with vinegar. I'm not a chemist, but I think it better predisposes the root to release the coloring principles by breaking down the glucose molecules. Regarding iron sulfate, I think it is ferrous sulfate, the one anciently called green vitriol, which consists of transparent green salt crystals. Used in place of alum, it produces a dark brown lake. When used in small amounts is useful for cutting down the excessively bright orange-red of lakes fixed on alum. The same purpose for which lamp black (carbon black or vine black) is used, but with a lower opacity of the pigment, which is, however, less transparent than the red lake fixed on alum (so use it sparingly). Madder fixed with zinc sulfate (white vitriol in ancient times) gives a redder lake with less tendency to orange than alum, although it is a somewhat bright and crude red. For anyone interested in pigment making, a must-read book is Jo Kirby's Natural Colorants. https://www.kremer-pigmente.com/en/shop/books-color-charts/992405-kirby-et-al-natural-colorants-for-dyeing-and-lake-pigments.html

For rosinate making, I suggest referring to the really good work and article by @JacksonMaberry. I believe that he is the one who has studied this aspect in greater depth.

 

[LCF]

7 hours ago, M Alpert said:

@HoGo - sounds like @LCF has a better understanding of the chemistry than I do. I have imagined it is making a sort of zinc-alizarin rosinate, but I don't really know.

Not really, that is more or less the same thing! It defies accurate description.  Even plain zinc rosinate is not a straight 1:2 stoichiometric arrangement.

Yesterday I was sorting various oil, resin, varnish, colourant papers I have printed into folders  and it made a pile about 600mm high not including various books I own or downloaded but I still don't understand all the complexities of it.

 

I'm pretty keen to try the zinc and aluminium madder versions now. And tin. As soon as the dangerously dry and hot weather here calms down it will be cooking time again. 

 

 

[uguntde]

13 hours ago, Davide Sora said:

Yes, I also do the roots fermentation with vinegar. I'm not a chemist, but I think it better predisposes the root to release the coloring principles by breaking down the glucose molecules. Regarding iron sulfate, I think it is ferrous sulfate, the one anciently called green vitriol, which consists of transparent green salt crystals. Used in place of alum, it produces a dark brown lake. When used in small amounts is useful for cutting down the excessively bright orange-red of lakes fixed on alum. The same purpose for which lamp black (carbon black or vine black) is used, but with a lower opacity of the pigment, which is, however, less transparent than the red lake fixed on alum (so use it sparingly). Madder fixed with zinc sulfate (white vitriol in ancient times) gives a redder lake with less tendency to orange than alum, although it is a somewhat bright and crude red. For anyone interested in pigment making, a must-read book is Jo Kirby's Natural Colorants. https://www.kremer-pigmente.com/en/shop/books-color-charts/992405-kirby-et-al-natural-colorants-for-dyeing-and-lake-pigments.html

 

Madder contains a glycoside (a molecule mad eof several suger entities) of alizarin. This has to be cleaved to make alizarin and alizarin metal salts. Historically this was done by enzymatic cleavage of the glycosides, by immersing the plant homogenates for long times (year(s)) - not a fermentation but a biochemical reaction.

You can cleave the glycosidic bond much easier with acid or a base. This is what your vinegar does, but not very well - your yields will be very low.

Chemically this is done with strong bases or acids - some of these old recipes use strong bases (the ones I find in George Fry's book). Here some recipes (in German): https://illumina-chemie.org/viewtopic.php?t=5674

You can also bye enzymes to do this but they will be hard to find. See for example:
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/epdf/10.1002/pca.694

Some metal salts, in particular divalent metals (Fe2+) will form nice colored complexes of the free alizarin, looking like this:

 

These complexes can take more complex shapes with several metals as below.

 

 

These alizarin metal complex dyes will all dissolve in organic solvents, and oil is in this case a solvent, best when heated, and likely even in alcohols (if there is not too much water in it, I would try propanol). Hence they are not pigments but soluble dyes.

In old times fabrics were treated with olive oil and alizarin was applied as aluminium acetate or sulfate.

 

 

[Davide Sora]

1 hour ago, uguntde said:

 

Madder contains a glycoside (a molecule mad eof several suger entities) of alizarin. This has to be cleaved to make alizarin and alizarin metal salts. Historically this was done by enzymatic cleavage of the glycosides, by immersing the plant homogenates for long times (year(s)) - not a fermentation but a biochemical reaction.

You can cleave the glycosidic bond much easier with acid or a base. This is what your vinegar does, but not very well - your yields will be very low.

Chemically this is done with strong bases or acids - some of these old recipes use strong bases (the ones I find in George Fry's book). Here some recipes (in German): https://illumina-chemie.org/viewtopic.php?t=5674

You can also bye enzymes to do this but they will be hard to find. See for example:
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/epdf/10.1002/pca.694

Some metal salts, in particular divalent metals (Fe2+) will form nice colored complexes of the free alizarin, looking like this:

 

These complexes can take more complex shapes with several metals as below.

 

 

These alizarin metal complex dyes will all dissolve in organic solvents, and oil is in this case a solvent, best when heated, and likely even in alcohols (if there is not too much water in it, I would try propanol). Hence they are not pigments but soluble dyes.

In old times fabrics were treated with olive oil and alizarin was applied as aluminium acetate or sulfate.

 

 

Thanks for chiming in and making up for my lack of chemical knowledge. Much appreciated!

[uguntde]

29 minutes ago, Davide Sora said:

Thanks for chiming in and making up for my lack of chemical knowledge. Much appreciated!

In essence: Alizarin can be made much more efficiently and with much better yield when done properly. I would buy alizarin, to be honest.

[LCF]

On 4/9/2025 at 2:54 AM, Bodacious Cowboy said:

Gosh. I've been making colophony/mastic/linseed oil varnish for over 20 years and according to the above posts I've been doing everything wrong.....

Cook colophony for 40 hours or so at just above the melting point - relatively low weight loss, huge colour change.

Liberally thinned with mineral spirits - no problem.

No siccative

"String test"? I don't even know what that means,

 

And yet, my varnish is a very nice colour, brushes on nicely, dries in about 8 hours in the light box, is acceptably wear resistant, doesn't print and folks tell me it looks lovely. 

Good oil makes it work usually. I used to cook the oil and resin together at ridiculously high temperatures and still used driers to be sure ... but I think that cooking the resin very high gives it an opacity and a slightly greenish burnt look. I suspect that at higher temperatures resin goes through a gummy phase, breaking down to something? plus the rosin oil which boils off. The rosin oil is created by the breaking down of the resin.

 

After reading this paper from 1954 ( a good year!) I have cooked it lower and longer. It usually ends up a traffic light red but not dark enough to have much colour in the varnish. I also add callitris resin (= sandarac) which toughens it. I might try your 40+ hour recommendation.

stinson1954 (1).pdf

[MikeC]

Wasn't it in Roger's bass thread where he cooked rosin long and low temp?   

Anyway,  I didn't mean to turn my varnish making thread into a lake making thread but here' my attempt at madder lake mixed with a little varnish and on a sample in the sun.  Sun makes color phot oversaturated but I think the color in the photo is accurate.  There was a yellowish undertone in the wood already before I put the varnish sample on so don't mistake that for the varnish color.    Not as pink as I was expecting just looking at the dry lake powder.  

 

[David Burgess]

21 hours ago, LCF said:

Good oil makes it work usually. I used to cook the oil and resin together at ridiculously high temperatures and still used driers to be sure ... but I think that cooking the resin very high gives it an opacity and a slightly greenish burnt look. I suspect that at higher temperatures resin goes through a gummy phase, breaking down to something? plus the rosin oil which boils off. The rosin oil is created by the breaking down of the resin.

After reading this paper from 1954 ( a good year!) I have cooked it lower and longer. It usually ends up a traffic light red but not dark enough to have much colour in the varnish.

If I'm not mistaken, this paper refers to rosin cooked in a pure or nearly pure nitrogen atmosphere, which would by highly unusual for violin makers.

In my many years of experimenting with cooking rosin (in normal air), I haven't been able to establish a major difference between cooking longer at lower temperature, and cooking for a shorter period at a higher temperature. Much more important has been the rate of air exchange (and the surface area of the resin exposed to air).. with this air containing oxygen, and also blowing away released volatiles to prevent them from re-incorporating into the resin.

[Steve Voigt]

6 hours ago, LCF said:

 

 

After reading this paper from 1954 ( a good year!) I have cooked it lower and longer. It usually ends up a traffic light red but not dark enough to have much colour in the varnish. I also add callitris resin (= sandarac) which toughens it. I might try your 40+ hour recommendation.

stinson1954 (1).pdf 495.9 kB · 5 downloads

The Stinson paper is IMO one of the two most valuable papers (for rosin varnish makers) to come out of the naval stores lab. Here is the other.

 

Thermal dimerization.pdf

[Steve Voigt]

1 hour ago, David Burgess said:

If I'm not mistaken, this paper refers to rosin cooked in a pure or nearly pure nitrogen atmosphere, which would by highly unusual for violin makers.

In my many years of experimenting with cooking rosin (in normal air), I haven't been able to establish a major difference between cooking longer at lower temperature, and cooking for a shorter period at a higher temperature. Much more important has been the rate of air exchange.. with this air containing oxygen, and also blowing away released volatiles to prevent them from re-incorporating into the resin.

Correct Dave, they excluded oxygen.

I've titrated a lot of samples and (informally) checked the softening points of rosin cooked at various times and temperatures. In general, the conclusions of the article hold true even when there is access to oxygen. The main difference is that softening point does not decrease at high temps the way it does when oxygen is excluded. But (I think) the main reason is that it's impossible with ordinary cooking equipment to avoid evaporating a significant portion of the rosin when cooking at high temps. 

 

[jefcostello]

As for cooking with rosin:

A: Use above 300-400 degrees Celsius
B: and use 100-130 degrees

For me, I have to reduce the rosin weight by 75%-80% to make it hard enough.

There is no difference to me in terms of color and hardness, the difference is the time it took to make.

[LCF]

12 hours ago, uguntde said:

 

Madder contains a glycoside (a molecule mad eof several suger entities) of alizarin. This has to be cleaved to make alizarin and alizarin metal salts. Historically this was done by enzymatic cleavage of the glycosides, by immersing the plant homogenates for long times (year(s)) - not a fermentation but a biochemical reaction.

You can cleave the glycosidic bond much easier with acid or a base. This is what your vinegar does, but not very well - your yields will be very low.

Chemically this is done with strong bases or acids - some of these old recipes use strong bases (the ones I find in George Fry's book). Here some recipes (in German): https://illumina-chemie.org/viewtopic.php?t=5674

You can also bye enzymes to do this but they will be hard to find.

 

 

Derksen et al 2003  found that soaking dried madder in plain water for 30m to a few hours activated a natural enzyme which broke down the glycosides and almost completely removed the toxic compound lucidin  (a mutagen) from the result.  Natural madder has a mix of colourants aside from alizarin. The Indian madder I use has a darker tone than the european, less pink and more to the purple end.

 

 The DIY 'ferment' gets good results.

 

 

" Chemical and Enzymatic Hydrolysis of Anthraquinone Glycosides from Madder Roots Goverdina C. H. Derksen,1 Martijn Naayer,1 Teris A. van Beek,1* Anthony Capelle,1 Ingrid K. Haaksman,2 Henk A. van Doren2 and Æde de Groot1 1 Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands 2TNO Nutrition and Food Research, Utrechtseweg 48, Postbus 360, 3700 AJ Zeist, The Netherlands

 

For the production of a commercially useful dye extract from madder, the glycoside ruberythric acid has to be hydrolysed to the aglycone alizarin which is the main dye component. An intrinsic problem is the simultaneous hydrolysis of the glycoside lucidin primeveroside to the unwanted mutagenic aglycone lucidin. Madder root was treated with strong acid, strong base or enzymes to convert ruberythric acid into alizarin and the anthraquinone compositions of the suspensions were analysed by HPLC. A cheap and easy method to hydrolyse ruberythric acid in madder root to alizarin without the formation of lucidin turned out to be the stirring of dried madder roots in water at room temperature for 90 min: this gave a suspension containing pseudopurpurin, munjistin, alizarin and nordamnacanthal. Native enzymes are responsible for the hydrolysis, after which lucidin is converted to nordamnacanthal by an endogenous oxidase."

 

 

[LCF]

8 hours ago, MikeC said:

Wasn't it in Roger's bass thread where he cooked rosin long and low temp?   

Yep.

8 hours ago, MikeC said:

Anyway,  I didn't mean to turn my varnish making thread into a lake making thread

Nah, let it rip! Varnish and colour are on everyone's mind.

 

 

8 hours ago, MikeC said:

but here' my attempt at madder lake mixed with a little varnish and on a sample in the sun. 

Interesting colours. 

Colours are hard to render on digital cameras. I was trying to take a photo of an astounding deep orange red sunset on my Samsung phone last night but the result was a measly yellow glow. There probably is an overzealous near infrared filter in it somewhere.  

 

[LCF]

 

2 hours ago, Steve Voigt said:

The main difference is that softening point does not decrease at high temps the way it does when oxygen is excluded. But (I think) the main reason is that it's impossible with ordinary cooking equipment to avoid evaporating a significant portion of the rosin when cooking at high temps. 

 

Thanks for that paper. 

 

A friend of mine was enthusiastic about an idea of David Rubios, to use rosin oil as a ground.  It is a gummy liquid which never seems to fully harden. Chemically it's a mix of lmw resin breakdown products of pyrolysis. It was a disaster! 

The interesting thing is how he made it. He put rosin in a lidded coffee can to which he attached a rough copper coil about 600mm long like an old fashioned still. Then cooked the daylights out of it and collected the liquid which came over at higher temperatures. I think if you cook resin at high temps it would be best to do it in a wide pan with serious smoke extraction. 

I'll speculate that cooking it in the oil at high temps might also trap some of those volatiles???

[MikeC]

8 hours ago, LCF said:

 

 

Thanks for that paper. 

 

A friend of mine was enthusiastic about an idea of David Rubios, to use rosin oil as a ground.  It is a gummy liquid which never seems to fully harden. Chemically it's a mix of lmw resin breakdown products of pyrolysis. It was a disaster! 

The interesting thing is how he made it. He put rosin in a lidded coffee can to which he attached a rough copper coil about 600mm long like an old fashioned still. Then cooked the daylights out of it and collected the liquid which came over at higher temperatures. I think if you cook resin at high temps it would be best to do it in a wide pan with serious smoke extraction. 

I'll speculate that cooking it in the oil at high temps might also trap some of those volatiles???

Any idea of what the temp need to be to distill off the rosin oil?  

[LCF]

23 minutes ago, MikeC said:

Any idea of what the temp need to be to distill off the rosin oil?  

I will ask him but I think if you get rosin to the temperature where it starts to give off volumes of acrid smoke, it will be somewhere near there. Watery stuff comes off at a lower temperature which you can ignore. Same stuff as makes the resin fuzz when you go past the melting point. There are details of temperatures and times in the paper which Steve posted but I'm having trouble decoding the jargon used. 

Ps to clarify, the rosin oil isn't there to begin with, to be distilled off. The cooking breaks the resin down and the oil comes across in the smoke. 

Edited April 13 by LCF
Ps

[LCF]

Just an aside related to oil cooking:

 

Everyone says you can't make a varnish from olive oil although small amounts of oxidised oleic acid are found in some old artworks. I'm a bit embarassed to show my dirty dishes but tonight when I was cooking dinner I overheated a little olive oil in the bottom of a stainless frypan and it has made an extremely tough orange film which is a b#$$÷r to clean off. I've done it before, solvent won't remove this, it takes washing soda and a scourer. 

 

Just a data point!

[MikeC]

That's interesting,  I wonder if you could make varnish with olive oil.  

Well I found my espresso machine!  I thought it was gone.   

I just ran some of the madder root powder through it and got a much more concentrated color solution,  so I'll try making lake again today.   

I'm a little confused on the proportion of alum to carbonate.  In the Neil Ertz recipe it was equal amounts but then I read on one of these old threads to use half as much carbonate as alum.