Help Needed, Troubleshooting My Oil Varnish-Making Process

[Steve Voigt]

On 12/14/2024 at 4:34 PM, Sean Couch said:

In those instructions, the 168 hour cook time for colored varnish is explicitly called out. My 168 hour varnish didn’t have enough color. I contacted the author of the varnish making tutorial and he mentioned that the reduction amount is important and not the time. He recommended to go for at least a 50% reduction in colophony weight and a 67% reduction would be ideal.

 

I just want to mention that my experience is different. I have cooked at many different temperatures and durations, and with different evaporative conditions. My conclusion is that color is not dependent on the amount of reduction. Obviously, some evaporation is necessary, but one can get dark color with 20% reduction or 80% or anything in between. If you cook in a pot with a pour spout, and leave the lid on, you will get slow evaporation and recirculation. You will need to cook longer than you would if you left the lid off, but you will eventually get to the same color.

What is different is all the other attributes of varnish: hardness, touch to dry time, cure time, chipiness, etc. A resin that has been reduced by 80% will be almost copal hard, and will tack extremely quickly…maybe too quickly. Whereas, a resin that has been reduced by 20% will not be as hard, but will allow more open time. So, by controlling evaporation relative to color, you can get the characteristics you want.

Recommendations like "cook for 168 hours at x temperature" are quite useful as a starting point, but only that. As I said, evaporation will have a big effect on how quickly the resin darkens…but many other factors, like the size and shape of the pot, or external weather conditions, will also effect how long the process takes. As I gained experience, I found it far more useful to assess color as the cook proceeded, stopping when the color was right. Color is best judged by by observing the resin as it drips off a stirring rod, forming fine filaments. A resin may look very dark in mass amounts, but may still be blond in fine strands. This kind of thing is hard to describe adequately and experience is the best teacher.

[LCF]

On 12/16/2024 at 7:34 AM, jefcostello said:

Tell me about my experience.
Burning rosin is to harden the varnish, not for color. Color is an added product.

 Many online recipes may only work in their region.
Cook the rosin to 15%-25%, oil:rosin > 0.66:1. This will make the varnish durable

I've seen a lot of high priced violins rot in my area. This may explain why most people now use commercial varnish instead of making their own. Because the maker doesn't know what will happen to its violin in the future

Adding mastic will make the varnish softer, and I recommend not making the recipe too complicated at first.

Is it the humidity where you are that tests your varnishes to the limit? I live near 35'S, not so humid usually but summer temps have just been near 40C for a couple of days with very low humidity. However, licking the edge of a dried varnish sample ( caveats apply !#*! ) is a useful test as to whether it will be stable against hot damp violinists.

 

Have you tested an oil cooked rosinate style varnish for stability,  such as those favoured by Jackson M.?

[jefcostello]

Hi Dear Mr. LCF

It is the limit of my test (fingerprint test). I will apply it with my hand to twice the standard thickness, and then do the fingerprint test for a week. If it passes the test, I'll package it.

In fact my limit is oil:rosin > 0.7:1. But I would say 0.6666 on the Internet

For brown violins use rosin oil varnish, 0.7:1. I don't use Shoulder Rest, I use it naked a lot and it seems ok so far. >Ultimate test

I took a photo of my latest test. The left side is 2000g > 300g, and the right side is 1000g > 500g. The right side fails the fingerprint test. They are both oil:rosin > 0.66:1

The brown violin is rosin oil varnish, and the red-orange one is spirit varnish. I put them together so that I can see the color of the test piece.

I have lived in both China and Taiwan. For me, the temperature is not the most terrible thing. Beijing often has weather above 40 degrees, with a relative humidity of 20%-40%. I know Australians will complain about being too dry

The relative humidity in Taipei is 70%-100%. (Dew will form on the house). I often joke with people, when I see a very soft new violin, I will say: Your violin will rot when it comes to Taiwan...

If you don't insist on using rosin, it is much better to use amber. It can reach Oil:Amber>1.1:1

Boil linseed oil at 250 degrees Celsius for 30 minutes and hours. The resulting oil is different, but there is no difference for fingerprint testing.

I know that boiling the varnish for a longer time will increase the hardness, but it is extremely unstable, probably due to weather changes and the paint being too soft. This is the only part I haven't researched...

[jefcostello]

I did a test by burning 1000g of rosin into 500g, 0.66:1 oil:rosin. A varnish was then made that failed the fingerprint test. This is all what I expected.

I burned it at 250-300 degrees Celsius for five hours before I threw it away. The result still failed the fingerprint test. And the color didn't get darker. It didn’t thicken either.

For me, the mixing time of the resin and oil only takes five minutes. If I wanted to do something different, I would separate the resin and oil

I've burned dozens of kilograms of rosin over the past two years.

The 94% in the picture is the relative humidity I had at that time. I am very skeptical about the formulas on the Internet, their availability, and maybe they are only suitable for certain specific areas.

If you want to burn the color, cook rosin in a large area at low temperature for a long time, such as a 30cmX30cm electric hot plate, but the more air there is, the more dangerous it is. When the rosin burns to the surface and begins to solidify, the hot plate cannot melt it. The rosin will be deep and hard.

The harder and darker the rosin in the paint, the shorter its opening time, Steve Voigt mentioned. What I do is add more lavender oil or turpentine.

Even though my rosin is 0.3mm, it still looks black in the sun.

[joerobson]

1 hour ago, jefcostello said:

The harder and darker the rosin in the paint, the shorter its opening time, Steve Voigt mentioned.

@jefcostelloIn my not so humble opinion.  I disagree.  The hardness and or color of the rosin in the cook does not effect open time.  This is controlled by the cooking of the components together and the addition or not of turpentine to the procedure.

on we go,

Joe

[jefcostello]

1 hour ago, joerobson said:

@jefcostelloIn my not so humble opinion.  I disagree.  The hardness and or color of the rosin in the cook does not effect open time.  This is controlled by the cooking of the components together and the addition or not of turpentine to the procedure.

on we go,

Joe

I believe you, but I have the same experience as Steve Voigt. Maybe you cook the rosin in a different way?

[joerobson]

1 hour ago, jefcostello said:

I believe you, but I have the same experience as Steve Voigt. Maybe you cook the rosin in a different way?

Quite likely!

[MikeC]

19 hours ago, joerobson said:

@jefcostelloIn my not so humble opinion.  I disagree.  The hardness and or color of the rosin in the cook does not effect open time.  This is controlled by the cooking of the components together and the addition or not of turpentine to the procedure.

on we go,

Joe

Joe,  what effect does the turpentine have in the cook?  Can you go into any detail on that?  

I like to apply multiple very thin coats when applying varnish.  The faster it dries the better.  

[joerobson]

6 hours ago, MikeC said:

Joe,  what effect does the turpentine have in the cook?  Can you go into any detail on that?  

I like to apply multiple very thin coats when applying varnish.  The faster it dries the better.  

@MikeC Well, as in all things varnish...it depends. I'll give some reluctant information.  This process is DANGEROUS.

When you cook resin and oil together you form a mixture.  When turpentine is added to cook you alter all the materials to form a compound.

The longer you cook the resin and oil together, the shorter the open time.

Brushing viscosity is a function of the brush and added (room temperature) turpentine.

Please be safe.

on we go,

Joe

[JacksonMaberry]

On 12/16/2024 at 1:46 PM, LCF said:

Have you tested an oil cooked rosinate style varnish for stability,  such as those favoured by Jackson M.?

Jefcostello, you should try cooked rosinate varnishes if you want to. Granted, it's not a magic bullet solution - like any varnish, if you don't prepare it carefully, it will not perform ideally. With making rosinate varnishes, the most challenging and most important factor for success is making sure the rosinates have been washed completely free of waste salts prior to drying and incorporation into the oil. 

I can provide you with a copy of my article on the subject if you write to me. 

The cooked rosinate oil varnishes I produce and sell under the JG McIntosh line are very resistant to moisture. With practice and diligence, you can make the varnishes just as well. 

[MikeC]

4 hours ago, joerobson said:

@MikeC Well, as in all things varnish...it depends. I'll give some reluctant information.  This process is DANGEROUS.

When you cook resin and oil together you form a mixture.  When turpentine is added to cook you alter all the materials to form a compound.

The longer you cook the resin and oil together, the shorter the open time.

Brushing viscosity is a function of the brush and added (room temperature) turpentine.

Please be safe.

on we go,

Joe

Don't worry, I'm an old man, been around long enough to know how to be safe.   Of course in my younger days well that's another story.     

    So if I understand correctly, in general, a longer cook makes a faster drying varnish.   And I can add turpentine to a finished varnish to thin it, which I did on the last build using some varnish that was given to me.  I like to apply it watery thin.

  I may eventually try some of your varnish if I continue to build more.  But I like to make things myself, with the exception of fittings like strings, pegs etc.  

[jefcostello]

5 hours ago, JacksonMaberry said:

Jefcostello, you should try cooked rosinate varnishes if you want to. Granted, it's not a magic bullet solution - like any varnish, if you don't prepare it carefully, it will not perform ideally. With making rosinate varnishes, the most challenging and most important factor for success is making sure the rosinates have been washed completely free of waste salts prior to drying and incorporation into the oil. 

I can provide you with a copy of my article on the subject if you write to me. 

The cooked rosinate oil varnishes I produce and sell under the JG McIntosh line are very resistant to moisture. With practice and diligence, you can make the varnishes just as well. 

Maberry

Thanks for your help, I know McIntosh. Different rosins can be obtained through chemical denaturation.

What I'm trying to say is that there are a lot of problems with recipes on the internet. I think I've used heat as far as it can go.

The issue of rosin varnish has been mentioned by many people. I guess I'm not the first to find out.

[Claudio Rampini]

11 hours ago, MikeC said:

So if I understand correctly, in general, a longer cook makes a faster drying varnish.   And I can add turpentine to a finished varnish to thin it, which I did on the last build using some varnish that was given to me.  I like to apply it watery thin.

It depends by the varnish, generally I don't like to cook the varnish for a long time because the oil will oxidize faster becoming "rubbery", for this reason I'm using the raw not boiled cold pressed linseed oil. Regarding the turpentine, be careful to adding it for a "watery" varnish, because more turpentine, more the varnish is loosing its light (it is not true for all the varnishes, but you have to find your balance. Thin layers are a very good thing, for this reason I like to use my finger to apply my varnish, generally I'm not diluting my sandarac varnish over 1:1 varnish/turpentine dilution.

[Steve Voigt]

On 12/22/2024 at 9:55 AM, jefcostello said:

The harder and darker the rosin in the paint, the shorter its opening time, Steve Voigt mentioned. What I do is add more lavender oil or turpentine.

 

On 12/22/2024 at 11:04 AM, joerobson said:

In my not so humble opinion.  I disagree.  The hardness and or color of the rosin in the cook does not effect open time.  This is controlled by the cooking of the components together and the addition or not of turpentine to the procedure.

 

On 12/22/2024 at 12:42 PM, jefcostello said:

I believe you, but I have the same experience as Steve Voigt. Maybe you cook the rosin in a different way?

 

On 12/22/2024 at 2:13 PM, joerobson said:

Quite likely!

Yes, how the rosin is cooked, as I mentioned earlier, has a huge effect. Joe has said on this forum that he cooks at low temp and minimal evaporation. I think he has mentioned targets of 150° C and 10-20% reduction. If you use higher temps and/or large reductions in weight, you will indeed get shorter open times.

It's also worth mentioning that what Joe means when he talks about "adding turpentine to the cook" may be quite different from what people imagine. Since he hasn't talked about this publicly, I won't speculate. If you want to experiment with turps, be careful! Or, you could just buy some of Joe's varnish.

[joerobson]

1 hour ago, Steve Voigt said:

 

 

 

Yes, how the rosin is cooked, as I mentioned earlier, has a huge effect. Joe has said on this forum that he cooks at low temp and minimal evaporation. I think he has mentioned targets of 150° C and 10-20% reduction. If you use higher temps and/or large reductions in weight, you will indeed get shorter open times.

It's also worth mentioning that what Joe means when he talks about "adding turpentine to the cook" may be quite different from what people imagine. Since he hasn't talked about this publicly, I won't speculate. If you want to experiment with turps, be careful! Or, you could just buy some of Joe's varnish.

@Steve Voigt All the above about resin is correct as we have discussed.

I am reluctant to give more information about the use of turpentine as this is wear the cook becomes volatile. I don't want to be responsible for folks having problems

 

on we go,

Joe

[ernym]

While I do like making my own varnishes, purchasing from experienced varnish makers like Joe gives piece of mind knowing all the effort that goes into making a fiddle. I've used Joe's varnishes before making my first fiddle, on fixer uppers. I highly reccomend his Balsam Ground System. Used it on many of mine and will use it on my last fiddle builds.

[Steve Voigt]

32 minutes ago, joerobson said:

 

I am reluctant to give more information about the use of turpentine as this is wear the cook becomes volatile. I don't want to be responsible for folks having problems

 

on we go,

Joe

Yep, 100% agree. 

[Nick Allen]

OP, I make a varnish that's identical to yours, but different in the resin-oil proportions. 

If you use a high oil content, and apply it too thickly or too quickly, you'll have this wrinkling problem. 

You can also experience it if you don't let excess solvent off gas before you put it in UV. It will form a skin and not allow the under material to dry. 

My varnish dries beautifully, but I used 3:1 resin to oil. I also use kerosene with methoxypropanol as a solvent. 

Avoid cooking your varnish for color. It'll look good under full spectrum light (sunlight) but it'll look like shit in diffuse/indirect lighting situations. Especially fluorescent environments, which many indoor places are. 

Use color additives that modify the optical properties of the film. You actually don't want completely transparent l, because the varnish will look too simple. 

[JacksonMaberry]

4 hours ago, Nick Allen said:

OP, I make a varnish that's identical to yours, but different in the resin-oil proportions. 

If you use a high oil content, and apply it too thickly or too quickly, you'll have this wrinkling problem. 

You can also experience it if you don't let excess solvent off gas before you put it in UV. It will form a skin and not allow the under material to dry. 

My varnish dries beautifully, but I used 3:1 resin to oil. I also use kerosene with methoxypropanol as a solvent. 

Avoid cooking your varnish for color. It'll look good under full spectrum light (sunlight) but it'll look like shit in diffuse/indirect lighting situations. Especially fluorescent environments, which many indoor places are. 

Use color additives that modify the optical properties of the film. You actually don't want completely transparent l, because the varnish will look too simple. 

I have seen some of Nick's most recent varnish, and it was unbelievably beautiful to the eye. He works hard for it, and it pays off. Incredible fiddle, too. 

[Nick Allen]

On 12/26/2024 at 1:35 AM, JacksonMaberry said:

I have seen some of Nick's most recent varnish, and it was unbelievably beautiful to the eye. He works hard for it, and it pays off. Incredible fiddle, too. 

Thank you for the kind words. 

Varnish is such a lifelong pursuit that drives one to the absolute edge both financially and emotionally lol. 

But the results can be worth it. 

[JacksonMaberry]

15 minutes ago, Nick Allen said:

drives one to the absolute edge both financially and emotionally

Ain't that the truth... It's a sanity hole 

[Nick Allen]

4 hours ago, JacksonMaberry said:

Ain't that the truth... It's a sanity hole 

That's why I just use colophony. You can get 55 gallon drums of it for cheap lol. 

I also abandoned Diamond G. It's great stuff but not the only thing that works. 

[JacksonMaberry]

51 minutes ago, Nick Allen said:

That's why I just use colophony. You can get 55 gallon drums of it for cheap lol. 

I also abandoned Diamond G. It's great stuff but not the only thing that works. 

Would def be interested in what you're using now. I still have most of a pallet of diamond g that I sorted and vacuum sealed because I'm a tweaker like that, but always want to know what my options are. I'm also really lazy so once I figure out my stoichiometry I don't wanna do it again for a new lot lol

[ernym]

7 hours ago, JacksonMaberry said:

 I still have most of a pallet of diamond g that I sorted and vacuum sealed

A pallet, you hit the lottery? 

[ernym]

8 hours ago, Nick Allen said:

I also abandoned Diamond G. It's great stuff but not the only thing that works. 

Yup.