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ingredient to harden varnish/colorant


fiddlewallop
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Hi Oded,

It does not "destroy" the varnish. That's probably not the right term, but it increases the alkalinity of the varnish excessively to the point where it is difficult to reach a neutral state again, if you use the amount that Hill specifies. Perhaps if you use 1/4 of the amount he specified, you'd be alright. But I think I would just leave it out altogether, because it's too easy to reach a varnish that is too alkaline, and then you have to add a large quantity of valuable materials in order to reach neutrality again. That's just my experience.

-FW

If you do something and it doesn't work, doing the opposite isn't going to necessarily make it work better :-)

The key to making good varnish is to always use good ingredients from a reliable source and carefully follow a tested recipe. A lot like cooking a good meal. Once you've mastered the recipe and understand it well, then you can try changing it.

You have not gotten to the first step yet.

With cooked oil varnishes it's generally best to make a new batch rather than trying to 'fix' a bad batch. IMHO

But maybe I'm wrong ;-)

Oded

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It seems to me that hardening and siccative are 2 different notions. Many metal will work as siccative (the original one was probably lead but it's toxic so not very useful now) in that they will speed up the drying time but will they really change the nature of the varnish? Wouldn't it be more to the point to look for a varnish recipe that involves harder resins?

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If you do something and it doesn't work, doing the opposite isn't going to necessarily make it work better :-)

The key to making good varnish is to always use good ingredients from a reliable source and carefully follow a tested recipe. A lot like cooking a good meal. Once you've mastered the recipe and understand it well, then you can try changing it.

You have not gotten to the first step yet.

With cooked oil varnishes it's generally best to make a new batch rather than trying to 'fix' a bad batch. IMHO

But maybe I'm wrong ;-)

Oded

Oded,

Quite right. If the varnish is wrong out of the pot, you can't "fix" it. Use it on your garden fence and try again.

roberto,

I agree.

on we go,

Joe

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It seems to me that hardening and siccative are 2 different notions. Many metal will work as siccative (the original one was probably lead but it's toxic so not very useful now) in that they will speed up the drying time but will they really change the nature of the varnish? Wouldn't it be more to the point to look for a varnish recipe that involves harder resins?

My experience is small I've made about 6 oz. just for giggles,I made the balsam varnish (1 oz.) from the last thread ,(thanks Pete G.) Is looking pretty cool so far, with a soft -yet cured texture,

By siccative ,we're talking about any substance that increases the CURING speed of an oil varnish.Yes? and hardness is comparable to brittle .not ductile...One of the major points I got from the resin acid number thread, is that lowering the acid number toward neutral results in a harder varnish ,I'm fact checking here,am I right about this? would using ash with it's metals so act as a siccative also? as well as producing a harder finish? For some strange reason,right now,I believe that any thing in to the mix will affect the mix, if there is any chemical action. It's a matter of weights and measures,and

Thinking about Oded's point on direction, Deep thought for the day,If one is traveling east and yet wishes to go north- do not do the opposite.It's not a question of, "if it works better" as this implies that it works at all.

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Oded,

Quite right. If the varnish is wrong out of the pot, you can't "fix" it. Use it on your garden fence and try again.

Hi Joe,

Isn't this a bit of an extreme statement? I regularly tweak a batch after the initial cooking with no ill effect. Been doing it that way since the 90's with no long term problems either. If you are bent on having some kind of ideal polymerization (or cross linking since it's not strictly a polymer) in the varnish then perhaps you are correct. I will say that I have my doubts that there is an ideal since we're working with natural ingredients - essentially a soup that's a little too complicated to predict exactly. I prefer to balance look, workability and finished film a little more "holistically".

FW, can you add a little more resin to the batch? That would be the best way to harden it up. It's hard to guide you without seeing the stuff first hand, but that's the first place to try. You can also keep this batch to add to another one that is similar in ingredients and process but might have turned out to dry too hard.

As has been said, siccatives are more for getting the film to dry. It would be a shame to throw out this batch just because it's not perfect. If nothing else, you'll learn from playing around with it.

--Joe

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Hi Joe,

Isn't this a bit of an extreme statement? I regularly tweak a batch after the initial cooking with no ill effect. Been doing it that way since the 90's with no long term problems either. If you are bent on having some kind of ideal polymerization (or cross linking since it's not strictly a polymer) in the varnish then perhaps you are correct. I will say that I have my doubts that there is an ideal since we're working with natural ingredients - essentially a soup that's a little too complicated to predict exactly. I prefer to balance look, workability and finished film a little more "holistically".

FW, can you add a little more resin to the batch? That would be the best way to harden it up. It's hard to guide you without seeing the stuff first hand, but that's the first place to try. You can also keep this batch to add to another one that is similar in ingredients and process but might have turned out to dry too hard.

As has been said, siccatives are more for getting the film to dry. It would be a shame to throw out this batch just because it's not perfect. If nothing else, you'll learn from playing around with it.

--Joe

Joe,

You can add stuff to the varnish...just as you might add solvent for application purposes. But, once the varnish is cooked...proper cross-linking established...then it is a finished process...anything you do after that is a diluting the varnish...but not changing its essential nature.

on we go,

Joe

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proper cross-linking established...then it is a finished process..

on we go,

Joe

This assumes a perfect stoichiomety in your ingredients and that all reactions go to completion. If you're just talking about adding solvents, you're correct. But, you can reheat a batch and add a main ingredient to shift a property. Are you suggesting that there's a reaction that occurs during cooling that doesn't allow reheating?

Unless you are measuring every batch of ingredients with some pretty sophisticated equipment, there is inevitably going to be some unreacted material on one side of the equation or the other or even both. From what I can tell, there's always unreacted oil in the end of a cooking session so adding more resin if needed and cooking some more works for me.

I don't mean to put you on the spot, but would like to figure out this difference in opinion.

--Joe

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I reheat varnishes quite alot and often they turn out better in the end. My last batch of copal varnish didnt turn out right the first time but on reheating worked out great. I do have a few large jars of failed varnish which wouldnt dry at all even loaded with dryers.

One of the worst was linseed oil and rosin reacted with sulphur!!!

I dont know anyone who makes varnish to stoichiometric ratios. How do you weigh them out which parts do you use as the reactants .You will get lots of side reactions and some parts will remain unchanged.

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This is an interesting idea FC. I've never attempted copal varnish. I think I'll put it on my to-do list.

Thanks!

FW

You should find out which copal he is referring to there are lots of them and some are only soluble in alcohol :-)

You can buy good quality linseed oil from artist's supply places or Kremer Pigments an excellent supplier.

Oded

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I reheat varnishes quite alot and often they turn out better in the end.

I got tired of all the bottles of various commercial varnishes and stuff I'd made, so I dumped them all in a pot and cooked it down to the consistency I wanted. It works fine. But then, each of the separate varnishes was good, too... except those where I put in too much tung oil and dried wrinkly. They got diluted down so it's not a problem with the big Bucket O'Varnish. Naturally I could never repeat this recipie.

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This assumes a perfect stoichiomety in your ingredients and that all reactions go to completion. If you're just talking about adding solvents, you're correct. But, you can reheat a batch and add a main ingredient to shift a property. Are you suggesting that there's a reaction that occurs during cooling that doesn't allow reheating?

Unless you are measuring every batch of ingredients with some pretty sophisticated equipment, there is inevitably going to be some unreacted material on one side of the equation or the other or even both. From what I can tell, there's always unreacted oil in the end of a cooking session so adding more resin if needed and cooking some more works for me.

I don't mean to put you on the spot, but would like to figure out this difference in opinion.

--Joe

Joe,

Well you made me do my homework on this one....back into books I haven't visited in a while.

Keeping in mind that I am a cook, not a chemist....True....empirically I do not KNOW that all the reactions are 100% complete.

But I will say some stuff about what I do know.

First let's look at solubility. Combining resin, oil, and turpentine....each properly prepared....using correct procedures....combine in a way that the old texts refer to as mutual solubility...each combining with the other in a way that creates a substance [varnish] which is different from any of the individual components. Re-heating, in the presence of excess or added material, does not "open" the varnish to new bonding...it just melts the materials into one another...Perhaps someone with a background in colloidal material can explain this better...or correct what I am saying.

Second we need to look at the [extensive] references to "batch failure". There is "insufficient bonding" characterized by separation of oil upon cooling. There is "salting out" which is a condition where resin settles out of the solution upon cooling. The reason may be poor running of the resin, too much turpentine at the wrong temperature, or poor oil preparation. There are no references to re-heating the materials to re-combine them.

I was only able to find one reference to re-cooking varnish. This is from Crockett's Manual which we have discussed in the past: "If while making anything you cook it too much and it seems to decompose, at this particular time add some fine powdered rosin, slowly, and it will bring it back all right, so it can be used for a second quality of what you are making."

On the flip side...when you add material after cooking the varnish....How do you know what and how much to add?

Predictability in varnish making is difficult enough the first time around.

I am not saying "don't do this"...I am saying I would not do it for myself or any of the makers I work with.

open to discussion...

on we go,

Joe

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Joe,

Well you made me do my homework on this one....back into books I haven't visited in a while.

Keeping in mind that I am a cook, not a chemist....True....empirically I do not KNOW that all the reactions are 100% complete.

But I will say some stuff about what I do know.

First let's look at solubility. Combining resin, oil, and turpentine....each properly prepared....using correct procedures....combine in a way that the old texts refer to as mutual solubility...each combining with the other in a way that creates a substance [varnish] which is different from any of the individual components. Re-heating, in the presence of excess or added material, does not "open" the varnish to new bonding...it just melts the materials into one another...Perhaps someone with a background in colloidal material can explain this better...or correct what I am saying.

Second we need to look at the [extensive] references to "batch failure". There is "insufficient bonding" characterized by separation of oil upon cooling. There is "salting out" which is a condition where resin settles out of the solution upon cooling. The reason may be poor running of the resin, too much turpentine at the wrong temperature, or poor oil preparation. There are no references to re-heating the materials to re-combine them.

I was only able to find one reference to re-cooking varnish. This is from Crockett's Manual which we have discussed in the past: "If while making anything you cook it too much and it seems to decompose, at this particular time add some fine powdered rosin, slowly, and it will bring it back all right, so it can be used for a second quality of what you are making."

On the flip side...when you add material after cooking the varnish....How do you know what and how much to add?

Predictability in varnish making is difficult enough the first time around.

I am not saying "don't do this"...I am saying I would not do it for myself or any of the makers I work with.

open to discussion...

on we go,

Joe

Thanks for the effort Joe. I know how hard reading is :)

I have to correct my first statement. It should have said "proportions to match the stoichiometry" not just stoichiometry. Even that is a bit of a stretch in my mind since we're talking soup.

I've also read statements of mutual solubility. Can't say how heat will affect yours since I'm not privy to your methods. I don't see any reason that reheating would cause issues with my own varnish and I haven't ever experienced any issues with drying, separation, salting out etc. Not bragging, just sayin' or just been lucky. I'm not ultra careful (or cavalier) in my methods either. Not to mention that it's being used by a number of makers for going on 20 years now and none of them have been able to break it yet. If I may brag a little - it's also been on a number of award winning instruments which is a real feeling of accomplishment.

One observation that shows that there are unreacted materials (or at least extremely weak bonds) in a varnish like you describe with resin, oil and turpentine is the immediate smell of turpentine when you open the jar or apply it. The turps will also affect the re-cooking. Turps boils at around 175C the oil and resin combine at a temp that's 100C+ higher than that. The temp of the mixture won't exceed the boiling point of the turps by much (if any) until it evaporates and so, the reaction isn't going to happen. So, there's the rub as simple as it is.

Many years ago I actually had a friend run my finished varnish through a chromatograph as well as samples of the original unmixed components. We compared them and found that there were unreacted components in the finished varnish. Proof enough for me.

The flip side you're asking about is this: At this point I just do it. I've made it enough that I just add what it feels like it needs after trying it out on a test strip. Since I've never had drying issues or separation etc. issues, I just work on brush-ability and then the properties of the dry film. Mostly done with oil proportions in small increments - change it, test it, change it, test it, settle on something that's close enough.

--Joe

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Doesn't Sandarac resin have a reputation for contributing hardness to the final varnish?

Also, I would think some types of fillers like silica might contribute a sort of 'hardness' to the end result.

Sandarac does have a reputation of making a hard film. Straight jacket is one way that I've heard it described. Not sure about the silica, but it seems like it would add hard bits in a film that has its own properties.

--Joe

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I know others have said that you should not reheat varnish. Hill, in particular, states this, "You can not reheat the varnish without destroying it so you have only one opportunity to get the turpentine incorporated." I think I might have read Darnton mention this as well. Because of these warnings, I have never tried it.

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Here's a question for the more experienced varnish makers:

Is it possible to take some ready made oil varnishes of different properties and blend them proportionally to utilize their specific desirable properties; or is it better to cook the desired resins all together at once and then combine with the oil in a single process?

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Here's a question for the more experienced varnish makers:

Is it possible to take some ready made oil varnishes of different properties and blend them proportionally to utilize their specific desirable properties; or is it better to cook the desired resins all together at once and then combine with the oil in a single process?

Hi Bill,

As soon as you say the word "better" it becomes a matter of judgement. From my own experience, I will say that you can blend ready made varnishes to take advantage of the properties as long as they are of similar composition. Mixing spirit varnishes with oil varnishes shouldn't work. I say "shouldn't" because people are clever. There was a student at NBSS that was so determined that he was able to dissolve orasol dyes (that would otherwise not do so) in oil varnish by first dissolving the dyes in alcohol an then added mineral spirits drop-wise to this mix until he reached a level of mineral spirits that allowed the concoction to dissolve in the oil varnish. It worked out pretty well in the finnished film as well. I'm digressing.

The properties of the wet varnish, like brush-ability and color can certainly be shifted by mixing. A varnish that is too stiff can become easier to apply by adding one that is looser. Colors also mix as you would expect in terms of hue, saturation, intensity etc.

The dry film will also shift as others have mentioned above. A tough varnish mixed with a friable one will end up somewhere in the middle. Again this is from my own experience with my own varnish. Others may find otherwise.

Although I haven't experience it, I suppose you can get issues with them not mixing well or strange problems like streaking, drying etc. I would suggest keeping the oils the same in both batches to be mixed. I haven't done it first hand, but my gut tells me that it's best not to mix walnut and linseed oil. Others might pipe in and tell of their experience here.

Better or not is a judgement call. I have violins that have been varnished with mixed batches that are old enough now without ill effect that I trust it.

--Joe

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Here's a question for the more experienced varnish makers:

Is it possible to take some ready made oil varnishes of different properties and blend them proportionally to utilize their specific desirable properties; or is it better to cook the desired resins all together at once and then combine with the oil in a single process?

Making your own varnish carries with it more risks than using something known and tested. Therefore it's better to make your varnish from a reliable, historical recipe using ingredients from a reputable and trusted source. Mixing ready made varnishes and hoping that the properties will combine seems too risky to me. But if you're adventurous and have a good protocol for testing the results, why not? Go for it!

Oded

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