Varnish making... and Lake making

[LCF]

28 minutes ago, MikeC said:

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

Not easily. It usually fails to dry.  In the frypan it's a thin layer over a wide area so lots of oxygen and maybe there is something in the stainless which acts as a catalyst. 

 

28 minutes ago, MikeC said:

   

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.   

 

Usually you titrate it, ie add the second solution until it stops fizzing. Then let it settle. I'm not sure but probably better to have a slight excess of alum. 

 

[uguntde]

On 4/8/2025 at 10:32 AM, Davide Sora said:

Good! Keep us updated.

We built an apparatus, simple from a chemist's point of view. We will

1. Dissolve rosin (maybe two different ones)

2. DIssolve linseed oil (also two batches)

3. Dissolve rosin in hot linseed oil

4. Cook for a day

5. Heat rosin to 250°C (or 350°C?) and take samples every day - this is the more complicated experiment, we will colled eaporating gases in a cold trap

6. Cook rosin in linseed oil

One question is whether we should control the gas over the heated liquids, but we certainly don't want nitrogen.

Any further ideas?

[MikeC]

Here's the results from the espresso machine.  Much more color extraction.   The problem now is that with this much dye solution, I don't know how much alum and carbonate to use.   

 

[uguntde]

5 minutes ago, MikeC said:

Here's the results from the espresso machine.  Much more color extraction.  

 

I am only interested to see what is happening chemically. We will run NMR and mass spec from the fractions.

[David Burgess]

16 hours ago, Steve Voigt said:

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.

Yes, I think it's oxidation which is mostly responsible for significantly darkening the color of the resin, and increasing the melting temperature.
How quickly this happens will also depended on the amount of resin surface area exposed to air.

[LCF]

1 hour ago, MikeC said:

Here's the results from the espresso machine.  Much more color extraction.   The problem now is that with this much dye solution, I don't know how much alum and carbonate to use.   

 

 

When you have added your first quantity of reagents, settle the lake and filter it out, then if the supernatant still has much colour, add a little more base + alum to it.  

Another suggestion if you're feeling experi-mental, before you run the madder powder  through your espresso machine soak it in minimal warm water for an hour or two. Add that water to the same jar as the extract. Then make the brew from the wet madder. 

 

[MikeC]

Too late to try that.    I dissolved 50 grams alum in 200ml water and stirred that in to the madder extract.   Then I slowly added in the sodium carbonate to avoid it foaming over the jar,  it's a liter mason jar,  really need something bigger. 

I used 25 grams sodium carbonate dissolved in hot water.  

This is looking a lot better than my first batch of pink lake.   

[LCF]

I just mushed up 25g into a slurry and will brew it in the morning. Note the use of offically approved Vegemite jar. V for very useful. 

Updated: This worked better than using the madder dry. The colour came through the portafilter for longer and it is more intense. I ended up with 600ml of liquid from my 25g madder including a nice 'crema' froth. Also different this time is that the stainless metalwok got stained and the colour is hard to budge. I put the spent sludge back in the jar with fresh water and a little vinegar to see if more colour can be got. 

Edited April 14 by LCF
Updated pics

[Steve Voigt]

1 hour ago, uguntde said:

We built an apparatus, simple from a chemist's point of view. We will

1. Dissolve rosin (maybe two different ones)

2. DIssolve linseed oil (also two batches)

3. Dissolve rosin in hot linseed oil

4. Cook for a day

5. Heat rosin to 250°C (or 350°C?) and take samples every day - this is the more complicated experiment, we will colled eaporating gases in a cold trap

6. Cook rosin in linseed oil

One question is whether we should control the gas over the heated liquids, but we certainly don't want nitrogen.

Any further ideas?

Regarding rosin, You might want to look at the paper I posted, so you don’t duplicate their results. I suggest cooking at 220-230, which according to the paper is the lowest temp at which rosin dimerizes at a reasonable rate. They found that in an anoxic environment, maximum dimerization without a catalyst occurs after about 100 hrs at 225. They also did a run for 16 hrs/230 c in an oxic environment and got some interesting results. So I think the interesting question is, what happens after say, 100 hrs/230 c in an oxic environment? Do longer chain oligomers form?

Evaporation is a key variable here…if you reflux in an oxic environment, the results will be very different than if you let all the volatiles escape. In the latter case, you will probably end up with something that is largely dimers and short chain oligomers. (Is it feasible to reflux with access to O2? I have no lab experience.)

A big picture comment…your list above covers a lot of territory. It’s wide but not deep. It’s probably enough for half a dozen research papers, at least. If I were doing the rosin experiment, I’d probably cook at 25 degree increments from 150-300, at varying durations, amount of access to oxygen, and amount of evaporation. The number of trials that would be needed is mind boggling! So, it might be worthwhile to narrow your focus. Sounds interesting though; kudos for tackling this! While I’ve largely answered my own questions about cooking rosin from a practical standpoint, I would sure love to know more about what is actually happening on a molecular level.

[LCF]

6 hours ago, Steve Voigt said:

Regarding rosin, You might want to look at the paper I posted, so you don’t duplicate their results. I suggest cooking at 220-230, which according to the paper is the lowest temp at which rosin dimerizes at a reasonable rate. They found that in an anoxic environment, maximum dimerization without a catalyst occurs after about 100 hrs at 225. They also did a run for 16 hrs/230 c in an oxic environment and got some interesting results. So I think the interesting question is, what happens after say, 100 hrs/230 c in an oxic environment? Do longer chain oligomers form?

Evaporation is a key variable here…if you reflux in an oxic environment, the results will be very different than if you let all the volatiles escape. In the latter case, you will probably end up with something that is largely dimers and short chain oligomers. (Is it feasible to reflux with access to O2? I have no lab experience.)

 

In that paper after the cooking phase they recovered a significant portion of high grade resin from their distillate. I wonder how feasible it is to do that recoverybin a low key setup? Presumably that could be fed back into another round of the cooking process? 

 The softening point temperature of their residue only ever gets lower than the initial value but if I am understanding what you wrote earlier, you find that it increases after cooking in air?

I wonder if a two phase cooking process would give a better yield ? Initial phase would be long with a more restricted exhaust so it tends more to being anaerobic followed by a shorter evaporation phase.  That is something which @uguntde might be able to evaluate.

 

 

[Steve Voigt]

16 hours ago, LCF said:

 

In that paper after the cooking phase they recovered a significant portion of high grade resin from their distillate. I wonder how feasible it is to do that recoverybin a low key setup? Presumably that could be fed back into another round of the cooking process? 

 

 

 

It doesn’t sound too difficult….just a condenser and some tubing. 

 

16 hours ago, LCF said:

 

 

 The softening point temperature of their residue only ever gets lower than the initial value but if I am understanding what you wrote earlier, you find that it increases after cooking in air?

 

 

 

Yes, but again I don’t know if that was due to the presence of oxygen, or just to the low-bp volatiles evaporating. Or both.

16 hours ago, LCF said:

I wonder if a two phase cooking process would give a better yield ? Initial phase would be long with a more restricted exhaust so it tends more to being anaerobic followed by a shorter evaporation phase.  That is something which @uguntde might be able to evaluate.

 

 

I had a similar idea once…cook at 220-230 with the lid on for about 100 hours to get maximum dimerization, then lower the temp to 150 and cook with lid off to evaporate the volatiles. But what I found is that the first phase produces the results I want, so no need for phase two. Also, I think my idea wouldn’t work—the first phase would raise the melting point, resulting in formation of a skin in the second phase. And a skin is always bad in my experience—it leads to partial insolubility. Now, if you could reflux it for a hundred hours, and then pull a vacuum and distill all the volatiles, in other words the same as they did in the paper (but in an oxic environment), you might get some interesting results. 

[LCF]

1 hour ago, Steve Voigt said:

It doesn’t sound too difficult….just a condenser and some tubing. 

 

That's exactly what my friend did to make the 'rosin oil' ground suggested by Rubio. I realise now that the whole soggy mess was exactly as described in the paper, mixed terpenes, pyrolysis products and mostly unconverted resin. Terrible  muck to put on a fiddle. He should have used the stuff that was left in the pot!

 

1 hour ago, Steve Voigt said:

I had a similar idea once…cook at 220-230 with the lid on for about 100 hours to get maximum dimerization, then lower the temp to 150 and cook with lid off to evaporate the volatiles.

 

What one needs is the perfect catalyst!

 

(Sulfuric acid???)

 

The best colour I ever had from rosin was a short cook with strong sodium hydroxide solution and a bit of oil but I was making rosin soap for leather, not varnish. 

 

 

 

[M Alpert]

5 hours ago, LCF said:

The best colour I ever had from rosin was a short cook with strong sodium hydroxide solution and a bit of oil but I was making rosin soap for leather, not varnish.

 

I've often wondered about that, as lye or soap is so efficient at extracting color. I guess some contributors here have had some experience with making a rosin soap at some stage of the varnish making process. I did once manage some version of that, but the result was less than spectacular.

It seems challenges expelling the water safely.

Thus we make lakes, attaching the dissolved coloring agent to a metal salt, precipitating and drying it. However, getting the lake to redissolve in the varnish is frustratingly elusive. Has anyone managed an easier solution for that?

@uguntde  did I understand right your earlier post about dissolving the dye of alizarin in oil? You referred to alizarin as a dye, not a pigment or a lake? Is this a trait that is unique to Alizarin? Or can you do this with other powdered color substances? I tried it also with the Alizarin Carmine from Kremer, it did not dissolve.

It never occurred to me to try to dissolve a lake in hot varnish, I wonder if that would work?!

[MikeC]

17 minutes ago, M Alpert said:

 

It never occurred to me to try to dissolve a lake in hot varnish, I wonder if that would work?!

That's something I'm going to try.  Might be a few days before I have some time for it though. . 

[MikeC]

How many times do you need to wash the lake / change the water?   The water in mine is clear but has a slight yellowish color still.   

[Steve Voigt]

6 hours ago, LCF said:

 

What one needs is the perfect catalyst!

 

(Sulfuric acid???)

 

 

 

 

Yeah, sulfuric acid became the preferred catalyst for polymerized rosin in the 1940s, and it still is. It creates a black sludge that needs to be washed out, thoroughly.

In the 30s, they used chlorides (zinc, aluminum, tin) as catalysts. Those also need to be washed out. I didn’t comment earlier on the whole Flaveta discussion, but your mention of catalysts reminded me why I’m leery. I did  a bunch of experiments with his method, and got some nice colors, but I can’t make peace with the idea of using huge amounts of salts and then leaving the waste products in the varnish. What happens in 5, 10, or 20 years? I don’t know….

[LCF]

42 minutes ago, MikeC said:

How many times do you need to wash the lake / change the water?   The water in mine is clear but has a slight yellowish color still.   

Are you filtering it in between or just syphoning off the water?

Wash, wash, wash.

 

 

[LCF]

54 minutes ago, Steve Voigt said:

Yeah, sulfuric acid became the preferred catalyst for polymerized rosin in the 1940s, and it still is. It creates a black sludge that needs to be washed out, thoroughly.

In the 30s, they used chlorides (zinc, aluminum, tin) as catalysts.

I've seen mention if finely divided tin as a catalyst.   Plain iron is a good catalyst for oil cooking but that's a different process. Sulphuric acid is a typical catalyst for esterification reactions and it also removes water from the reactants. Sodium and potassium methoxide are used in biodiesel esterification. 

 

The google AI answer to 'dimerisation if carboxyllic acids' is surpisingly lucid and it lists its references.

"Carboxylic acids dimerize through hydrogen bonding between two molecules, forming a stable, ring-like structure. This dimerization significantly increases the strength of intermolecular dispersion forces, leading to higher boiling points compared to similar compounds that don't dimerize. "

and

" Conditions:

Carboxylic acids are known to dimerize in the gas phase and in non-polar solvents, while in the presence of water, they tend to dissolve as individual molecules, forming hydrogen bonds with water instead. "

 Resins are not oils exactly but thus suggests that getting the water out of the mix is as important.

 

 

54 minutes ago, Steve Voigt said:

...  I can’t make peace with the idea of using huge amounts of salts and then leaving the waste products in the varnish. What happens in 5, 10, or 20 years? I don’t know….

 

Assuming 1:2 or 1:3 metal complexing to dye (to the resin) you could at least attempt to work out how much to use, and use much less. 

[LCF]

2 hours ago, M Alpert said:

I've often wondered about that, as lye or soap is so efficient at extracting color. I guess some contributors here have had some experience with making a rosin soap at some stage of the varnish making process. I did once manage some version of that, but the result was less than spectacular.

John Masters was on this wavelength, and FredN described a madder soap, looked fantastic. 

 

What I made, pic below, only took about 30 mins. It like an inverse Michelman soap with not much water. Not useful for varnish at that stage, it is a soap! You would have to precipitate it out and purify. 

 

2 hours ago, M Alpert said:

@uguntde  did I understand right your earlier post about dissolving the dye of alizarin in oil? You referred to alizarin as a dye, not a pigment or a lake? Is this a trait that is unique to Alizarin? Or can you do this with other powdered color substances? I tried it also with the Alizarin Carmine from Kremer, it did not dissolve.

I think it complexes with the resin. Try a bit of alizarin in hot resin if you have some spare mad scientist time. I read a paper about molten resin having affinity for some colourants, dyes. It is a powerful solvent and polar/non-polar. 

 

2 hours ago, M Alpert said:

It never occurred to me to try to dissolve a lake in hot varnish, I wonder if that would work?!

My memory might be faulty but I think Flavetta mentioned that. You could also try other metal lake types. It might solve the problem that Steve Voigt anticipates.

 

Resin soap was opaque in a jar:

 

 

[LCF]

 

7 hours ago, LCF said:

I think it complexes with the resin. Try a bit of alizarin in hot resin if you have some spare mad scientist time. I read a paper about molten resin having affinity for some colourants, dyes. It is a powerful solvent.

 

Here's that paper, free download from Nature:

 

https://www.nature.com/articles/153317a0

 

With the "Flavetta method" #1 there were no added metal salts. This is the version I have tried. M Alpert tried method #2 with added zinc chloride. Colour becomes more intense. 

 

[MikeC]

9 hours ago, LCF said:

Are you filtering it in between or just syphoning off the water?

Wash, wash, wash.

 

 

Just syphoning off the water and adding in fresh water,  rinse and repeat.   The water is clear but just has a slight yellowish tint.    Here in front of white paper towels so you can see it's just a hint of color in the water.  

[LCF]

On 4/14/2025 at 12:28 AM, MikeC said:

Too late to try that.    I dissolved 50 grams alum in 200ml water and stirred that in to the madder extract.   Then I slowly added in the sodium carbonate to avoid it foaming over the jar,  it's a liter mason jar,  really need something bigger. 

I used 25 grams sodium carbonate dissolved in hot water.  

This is looking a lot better than my first batch of pink lake.   

 

I read in my notes today that the technically correct ratio of Alum to Pot Carbonate is around 2.7:1 but it can depend on the pH of the dyestuff and the excess pf either gets washed out The amount of alum used typically equal to the weight of madder. Tomorrow I will mix up half of my new batch to alum and the rest to tin and iron lakes. Only those because I couldn't find the zinc and aluminium chlorides. 

 

@M Alpert Here's a frame grab from Flavetta's talk where a recipe for hot varnish plus lake pigment, cook for 30 seconds and pH? adjustment if necessary. Perhaps an acidic salt would develop the colour differently?

[MikeC]

11 minutes ago, LCF said:

Tomorrow I will mix up half of my new batch to alum and the rest to tin and iron lakes. Only those because I couldn't find the zinc and aluminium chlorides. 

 

Post pictures,  I'd like to see what it looks like with tin or iron.   

[Steve Voigt]

15 hours ago, LCF said:

John Masters was on this wavelength, and FredN described a madder soap, looked fantastic. 

 

 

Yes, oil soaps can make nice varnishes. This one is alizarin, with alum and lime.

 

[MikeC]

ok,  I'm lost now.   What's an oil soap varnish and how do you make it?   Is there an old link here somewhere?