Best Way To Refine Linseed Oil?

[NicholasP]

I’ve been washing some linseed oil and noticed there’s a huge mucal layer that formed. I wanted to ask if there’s anything that this mucal layer could be used for in violin making and if any of you have tried the salt method for refining linseed oil? I saw that many painters do this with salt in the water as it makes the oil and water separate very quickly compared to just water. Does it affect the oil for varnish making at all? Thanks in advance.

[JacksonMaberry]

Yes, washing the oil has an impact on the resulting varnish. Oil free of phospholipids and water soluble or sensitive sugars/proteins results in a more durable varnish which is more chemically resistant. Some prefer a varnish that is less durable and more prone to chemical attack by ethanol for antiquing, and would be less inclined to wash their oil. Different strokes for different folks.

There is no use for the mucilage in lutherie, or even the decorative and protective coating industry at large. It is thrown away, and a certain percentage of loss in refining is expected and budgeted for. 

The salt method is good, as is the plain water method though it is slower. Using a freezer helps with decanting. Read Tad Spurgeons papers, they deal exhaustively with the topic. 

For acid refining, read McIntosh, volume one. He discusses other methods as well, including alkali refining which is the most used method and results in what industry has termed "Varnish Makers Linseed oil". 

Whichever method you use, clarifying, bleaching, and bodying are further topics for exploration. 

So much has been written on the subject, and fortunately many of the valuable texts are in the public domain and available digitally for free. 

[Claudius]

I'm using a natural cold pressed linseed oil from Sweden. In general I think that these kind of products are already refined and ready to be used because they were refined/processed, so there isn't a visible mucilage in it (but if you know how to refine it further, it could have a better quality when making violin varnishes). It's different by the food grade linseed oil, where you can see visible mucilages, and you need to refine it (if you don't want to make a salad with it).

For these reasons I never tried to refine a linseed oil, and my varnishes never had a problem after 20 years from their application on a violin.

 

[JacksonMaberry]

3 minutes ago, Claudio Rampini said:

I'm using a natural cold pressed linseed oil from Sweden. In general I think that these kind of products are already refined and ready to be used because they were refined/processed, so there isn't a visible mucilage in it (but if you know how to refine it further, it could have a better quality when making violin varnishes). It's different by the food grade linseed oil, where you can see visible mucilages, and you need to refine it (if you don't want to make a salad with it).

For these reasons I never tried to refine a linseed oil, and my varnishes never had a problem after 20 years from their application on a violin.

 

As far as I am aware, the swedish oils labeled as Cold Pressed are only pressed and filtered. This does remove some of the mucilage, but wouldn't qualify in any respect as refined. 

But as you noted, that's ok! You don't absolutely have to refine the oil, whether by washing or otherwise - it's just a choice, which like any other has some impact on the final result. 

In general, washed and refined oils cure more quickly and to a harder, more durable film, but that's not to say unwashed oil will not cure at a reasonable rate. Obviously, the process of cooking any oil with resin to create a varnish will, to some extent, body and change the oil. The resulting mixture will have different curing characteristics to the unmodified oil, typically faster. 

There are really so many "levers" to pull in the process of selecting and preparing materials, then many more in the actual cooking of a varnish. All one can really do is read as much as possible, discuss as we're doing here now, and experiment thoroughly, often, and well. Eventually after a lot of time and a considerable amount of money spent one gets a varnish they're happy with. Haha!

[NicholasP]

2 hours ago, JacksonMaberry said:

Yes, washing the oil has an impact on the resulting varnish. Oil free of phospholipids and water soluble or sensitive sugars/proteins results in a more durable varnish which is more chemically resistant. Some prefer a varnish that is less durable and more prone to chemical attack by ethanol for antiquing, and would be less inclined to wash their oil. Different strokes for different folks.

There is no use for the mucilage in lutherie, or even the decorative and protective coating industry at large. It is thrown away, and a certain percentage of loss in refining is expected and budgeted for. 

The salt method is good, as is the plain water method though it is slower. Using a freezer helps with decanting. Read Tad Spurgeons papers, they deal exhaustively with the topic. 

For acid refining, read McIntosh, volume one. He discusses other methods as well, including alkali refining which is the most used method and results in what industry has termed "Varnish Makers Linseed oil". 

Whichever method you use, clarifying, bleaching, and bodying are further topics for exploration. 

So much has been written on the subject, and fortunately many of the valuable texts are in the public domain and available digitally for free. 

Thanks for recommending all these papers, they'll be very useful.

Unfortunate that the mucilage has no use for lutherie, maybe it'll be good on a salad or some fried rice, though the thought of it now is a bit off putting.

I don't have much interest at the moment in antiquing, so I'll probably go for the more durable varnish.

1 hour ago, Claudio Rampini said:

I'm using a natural cold pressed linseed oil from Sweden. In general I think that these kind of products are already refined and ready to be used because they were refined/processed, so there isn't a visible mucilage in it (but if you know how to refine it further, it could have a better quality when making violin varnishes). It's different by the food grade linseed oil, where you can see visible mucilages, and you need to refine it (if you don't want to make a salad with it).

For these reasons I never tried to refine a linseed oil, and my varnishes never had a problem after 20 years from their application on a violin.

 

My Linseed oil is Barlean's Organic and Unrefined Cold Pressed Linseed oil. So it's not the best oil for lutherie out of the box, though with proper refinement and washing I think it'll work.

[NicholasP]

Tiny little update. I removed all the mucus from the oil and added water with added salt this time. The difference of how quickly the water and oil separates now is astronomical. It's amazing how such a simple little thing like salt can change the process so much for the better.

[Claudius]

5 hours ago, JacksonMaberry said:

As far as I am aware, the swedish oils labeled as Cold Pressed are only pressed and filtered. This does remove some of the mucilage, but wouldn't qualify in any respect as refined. 

But as you noted, that's ok! You don't absolutely have to refine the oil, whether by washing or otherwise - it's just a choice, which like any other has some impact on the final result. 

In general, washed and refined oils cure more quickly and to a harder, more durable film, but that's not to say unwashed oil will not cure at a reasonable rate. Obviously, the process of cooking any oil with resin to create a varnish will, to some extent, body and change the oil. The resulting mixture will have different curing characteristics to the unmodified oil, typically faster. 

There are really so many "levers" to pull in the process of selecting and preparing materials, then many more in the actual cooking of a varnish. All one can really do is read as much as possible, discuss as we're doing here now, and experiment thoroughly, often, and well. Eventually after a lot of time and a considerable amount of money spent one gets a varnish they're happy with. Haha!

Thank you for your reply. I'm using a linseed oil/sandarac varnish, but in the past I used the modified colophony or amber, the oil didn't give me any problem. I like the cold pressed linseed oil because it's more fluid, and I'm avoiding to bring it over 200°C for a long time for not altering its good qualities. In few words, I'm heating the linseed oil, I'm not "cooking" it, in this way it remains clear and fluid (no "gummy" or a denser molasse), and dries forming a thinner and not sticky film. Regarding its siccative properties, the sandarac or the amber accelerate its siccativity and go out of the dust in about 1 hour (within in a UVbox), generally I can apply 1 layer every 12 hours. Sometimes the pigments accelerate its siccativity (iron oxides), but the madder lake it's slowing down just a bit.

[Chris Anderson, PhD]

Adding a 2nd recommendation to echo Mr. Mayberry's - I have found Tad Spurgeon's documents to be invaluable.  

Mr. Rampini - if you do not mind my question - how do you get the amber to combine with the oil without raising the temperature? 
What made you move to Sandarac/Oil varnish? 

Mr. Mayberry  - do you recommend a method for testing varnish for flexibility?  Do you think that adding durability detracts from the flexibililty of the final finish? 

-Chris 

[JacksonMaberry]

Just Maberry, no additional y. But autocorrect is probably to blame for that!

I am not certain of a quantitative method for such a test, but possibly there is an ASTM methodology or similar. I assess these things for my own uses qualitatively. 

The published properties of linoxin being what they are, it doesn't seem to me that linseed oil (washed or no) is the varnish ingredient to be feared. In my view, for whatever it's worth, the increased chemical resistance of washed oil and the modest increase in wear resistance is worth pursuing. 

The resin component, whatever it may be, is probably more worthy of scrutiny. In particular, I would think the hard fossil resins, as well as varnishes where the proportion of resin exceeds that of the oil dramatically, are more likely to have an impact by virtue of their rigidity. 

Of course, flexibility isn't a virtue in a vacuum. Damping is a consideration which impacts this. And in any case the varnish, assuming it's in the ballpark of reason in formulation and application, is probably low on the list of critical factors in acoustical/performance outcomes. More about staying out of the way of the carefully done work in selecting wood and shaping it suitably. 

At the end of the day, folks have been making great fiddles for about half a millennium, many of them without the "benefit" of professional science. 

[NicholasP]

Found the Tad Spurgeon papers today (link below). They truly are a marvel with what it covers. Too bad I don't have any sand that I'd trust to use with me. So salt and water will do for me (maybe the beach sand a kilometer from here will work though). I also forgot to add salt into the water when I changed the water... whoops. I'll heat the whole mixture up to warm-ish temperature and dump some salt into the jar, I'm hoping it won't affect the oil and will just bond with the water.

https://drive.google.com/file/d/1XtwT35P2S_1vxZqhfg6xvrV_YkU47ncl/view?pli=1

[Claudius]

5 hours ago, Chris Anderson, PhD said:

Mr. Rampini - if you do not mind my question - how do you get the amber to combine with the oil without raising the temperature? 
What made you move to Sandarac/Oil varnish?

I'm using classic old recipes from the XVI and XVII century, I'm lucky because we can find the linseed oil ready to be used, no need to refine it (but if you want do it, it will be better), but the problem is on the resins: colophony/rosin, sandarac, amber (this is what we can find on the original instruments). All the resins need pyrogenation, the colophony is easier to pyrogenize, but you need to cook it for a long time in an attempt to raise its melting point (for this reason we can add calcium and/or zync to do it). The colophony gives a beautiful varnish, but its melting point remains lower, whatever the method you are using to make it harder and more stable on the instruments.

Pyrogenizing the sandarac it's harder than the colophony, but the final varnish is pure and perfect to be used on the instruments, no more fingerprints or blackish wear areas. Recently sandarac based varnishes were found on few original cremonese instruments.

Pyrogenizing the amber is a VERY hard process, and it's very expensive, the final varnish is beautiful but sometimes it's harder than the other ones.

Once you have pyrogenated your resin, you are ready to make the varnish, and you can do it at temps around 200/250°C, this is the best method to preserve your linseed oil from the fast oxidation. Usually the best varnish is made with a 1:1 resin/oil ratio. Sometimes I'm adding small quantities of pyrogenized colophony and/or amber to the sandarac to make the varnish brighter and easier to apply.

In the attached photo you can see the varnish on a my 8 years old instrument, and how the varnish is wearing out. Usually my customers are asking me to NOT retouch these weared zones because they like it!

 

[Andreas Preuss]

14 hours ago, Claudio Rampini said:

I'm lucky because we can find the linseed oil ready to be used,

May I ask from where you are buying your linseed oil? 
 

I am wondering if you aren’t using a varnish receipe where a smaller amount of mucilage doesn’t matter.(Swedish oil seems to have lowest percentage of mucilage)  At least I know some violin makers who don’t proceed their oil. Instead they heat it once as you do. (Not sure if they stay below 200C.) 

16 hours ago, NicholasP said:

Found the Tad Spurgeon papers today (link below).

I always liked the method of Tad Spurgeon. It’s making the oil more fluid and it keeps longer in a jar without building a film. To save time I bought a 10 Liter jar and was shaking it every morning as a sort of physical exercise. When evaporating the remaining water it is good to stand by the pot to avoid overheating. It happened to me once with the result that the oil is getting darker and maybe less fluid. (Can be still used for varnish though. 
 

I found another method which claims to be faster. It’s mixing oil water and psyllium husks for removing the mucilage. 
http://www.calcitesunoil.com/Cleansing_Flax_Oil.html

I was about to try it but never got to do it, so I can’t comment on its advantages/disadvantages.

[Claudius]

11 hours ago, Andreas Preuss said:

May I ask from where you are buying your linseed oil? 
 

I am wondering if you aren’t using a varnish receipe where a smaller amount of mucilage doesn’t matter.(Swedish oil seems to have lowest percentage of mucilage)  At least I know some violin makers who don’t proceed their oil. Instead they heat it once as you do. (Not sure if they stay below 200C.)

I bought it from several shops: Cremonatools, Zecchi (Florence). The most important is to find a good cold pressed raw linseed oil. I learned this from the Eric Hebborn handbook, he found that the cold pressed raw linseed oil is much less sticky. Hebborn was known as a master forger, but he was much more than that: he was one of the last classic tradition painters.

[Andreas Preuss]

49 minutes ago, Claudio Rampini said:

I bought it from several shops: Cremonatools, Zecchi (Florence). The most important is to find a good cold pressed raw linseed oil. I learned this from the Eric Hebborn handbook, he found that the cold pressed raw linseed oil is much less sticky. Hebborn was known as a master forger, but he was much more than that: he was one of the last classic tradition painters.

Thanks, Claudio. The book of master forger Hebborn is indeed a great read. Though violin making isn’t making drawings or paintings, I think one can learn a great deal from Hebborn about the mindset to revive old artworks in their original style.

[Claudius]

9 hours ago, Andreas Preuss said:

Thanks, Claudio. The book of master forger Hebborn is indeed a great read. Though violin making isn’t making drawings or paintings, I think one can learn a great deal from Hebborn about the mindset to revive old artworks in their original style.

In the attached photo you can see a my drawing inspired to Piranesi, using the techniques that I learned on the Hebborn books. It was made using the ferrogallic ink (the same that Stradivari used for his purfling), and the "terra di Siena bruciata", a nice natural and transparent iron oxide that I'm using in my varnish oil/sandarac (you can find similar pigments in the classic old cremonese varnishes). The art of making violins comes from the pictorial tradition, they were using the same materials.

 

[NicholasP]

I've been shaking and shaking and so far the oil has hardly any more mucilage. Tomorrow I'll begin the regular water rinses. Should be done in a few days.

Edited August 2, 2024 by NicholasP
Changed my mind on doing the Marciana method

[ernym]

8 minutes ago, NicholasP said:

I've been shaking and shaking and so far the oil has hardly any more mucilage. But the water still ends up cloudy. Tomorrow what I'm going to do is try the Marciana method described by Tad Spurgeon. We'll see how it goes and how many mini eruptions I get.

The cloudiness is because there is still water trapped. You can clear the oil by heating it...SLOWLY...in a pan raising the temp to just under the boiling point of water. Spurgeon explains this step well.

[NicholasP]

23 minutes ago, ernym said:

The cloudiness is because there is still water trapped. You can clear the oil by heating it...SLOWLY...in a pan raising the temp to just under the boiling point of water. Spurgeon explains this step well.

According to Spurgeon, it should be slightly under or at 100C. But is it ok if the water is kept at a simmer? I don't have a thermometer on me so it's hard to know the temperature, but generally I know what output setting to set my propane stove for a simmer/kind of boiling.

[Claudius]

1 hour ago, NicholasP said:

According to Spurgeon, it should be slightly under or at 100C. But is it ok if the water is kept at a simmer? I don't have a thermometer on me so it's hard to know the temperature, but generally I know what output setting to set my propane stove for a simmer/kind of boiling.

It's better to use a dimmable electric stove.

[LCF]

When you warm the oil on a stove make sure there are no drops of water sitting on the bottom of the pot. That is a dangerous situation which can blow up in your face. 

 

I guess that's what you mean when you mention the Marciana method? If you want to literally boil the oil with water you need to use clean fine gravel or proper boiling chips in the bottom of the ppt. They minimise the cavitation. 

Edited August 2, 2024 by LCF
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