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Colophony Varnish Cooking


David Stiles
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Thanks for your replies. 

Recipe was to add a tablespoon of hydrated lime to 50g linseed oil.  I used dry powder and stirred it in to the oil while it was heating.   The linseed oil/ lime mix looked milky.  As I added it to the hot colophony, it just foamed a bit then quickly solidified.

After that failure, I started again and slowly added  a smaller quantity (1 level teaspoon) of lime to the colophony instead.  It foamed up at first and then went nice and clear after I mixed in linseed oil. 

So, I now have something that looks like varnish.  It has a good colour and the viscosity of honey.  Next is to test the drying.

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1 hour ago, David Stiles said:

Recipe was to add a tablespoon of hydrated lime to 50g linseed oil.  I used dry powder and stirred it in to the oil while it was heating.   The linseed oil/ lime mix looked milky.  As I added it to the hot colophony, it just foamed a bit then quickly solidified.

How much does a teaspoon of hydrated lime weigh?

A full tablespoon seems to me a lot for only 50g of oil, I would try to add only 0.5g (1%), little by little, making it incorporate during cooking. It should work and be more than enough.

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14 hours ago, Davide Sora said:

How much does a teaspoon of hydrated lime weigh?

Hi David,

A flat teaspoon of calcium Hydrate weighs in at 1.3g.  My combined weight of colophony, mastic, linseed oil & turpentine is 130g.  So I have 1% hydrated lime.   Is that too much?

 

 

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3 hours ago, David Stiles said:

Hi David,

A flat teaspoon of calcium Hydrate weighs in at 1.3g.  My combined weight of colophony, mastic, linseed oil & turpentine is 130g.  So I have 1% hydrated lime.   Is that too much?

The percentage must be calculated on the solid elements of the varnish, so you should not count the turpentine (assuming it is turpentine essence).

In any case the percentage is not rigid, it is usually indicated between 1% and 2%, I would prefer 1% because I am worried about the sensitivity to water that calcium hydroxide induces, but I am not a chemist and I rely on only about my feelings, so I might as well be proven wrong :)

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I used the same recipe for my first cook. It's a bullet proof, simple recipe when you don't know exactly how your ingredients react.

http://www.thestradsound.com/varnish

If you use the same ingredients, you can improve your varnish for every batch.

The colophony and linseed I use don't need lime. It turn out too hard and durable with liming.

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27 minutes ago, Michael_Molnar said:

I add a lime slurry. It is mostly water. I slowly squirt it into the hot varnish while stirring.

Another possibility is to add the lime in powder, and immediately afterward a few drops of water to start the reaction, stirring well. Works.

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7 minutes ago, David Burgess said:

How do you know that it is "bullet-proof? Have you not yet discovered that varnish properties can change over time?

— pilkunnussija. ;)

"bullet-proof" is a to exaggerate.

The point is for a first time cooker, that will get a good enough varnish following this simple recipe, for more or less unknown properties of the ingredients he/she buys for the first time cooking.

Don't take away the excitement for the first own made varnish, that will be awesome.

 

 

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27 minutes ago, Peter K-G said:

 

Don't take away the excitement for the first own made varnish, that will be awesome.

Unfortunately, the excitement of a self-made varnish (or any other sort of "self-training") will quickly fade, when one starts to go up against the best in the business. Some of these people are just really freakin' good!

Much of this will depend on ones goals. Does one aspire to be the best maker in the little town of Bumphuck, or aspire to something beyond that?

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59 minutes ago, David Burgess said:

Unfortunately, the excitement of a self-made varnish (or any other sort of "self-training") will quickly fade, when one starts to go up against the best in the business. Some of these people are just really freakin' good!

Much of this will depend on ones goals. Does one aspire to be the best maker in the little town of Bumphuck, or aspire to something beyond that?

I started varnish making because I could not buy what I wanted to have: high-resin with strong color, fragile enough to make shading with alcohol easy and the „right“ fluorescence. As far as I know, you cook your own varnish, too, don’t you?

 Of course it will take over a hundred batches until you might get a satisfying result, but it’s IMHO still worth it. 

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22 hours ago, Peter K-G said:

I used the same recipe for my first cook

That recipe was very helpful.  I suspect the large amount of Hydrated lime is not right though.  Depending on how one defines a tablespoon of it.  

I have just cooked colophony for a total of 11 hours.  It darkened for the first 2 hrs and then did not change much.  I started at 150deg and went up to 180deg for the last 5 hrs.  Its lost something like 15% of it's mass.   I would prefer it to be darker but I don't think it wants to be. 

 

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12 hours ago, Michael Szyper said:

I started varnish making because I could not buy what I wanted to have: high-resin with strong color, fragile enough to make shading with alcohol easy and the „right“ fluorescence. As far as I know, you cook your own varnish, too, don’t you?

 Of course it will take over a hundred batches until you might get a satisfying result, but it’s IMHO still worth it. 

Same here, I haven't been able to find an easy source of oil varnish here in Australia.  I hope it doesn't take 100 batches.  My second batch looks good, goes on well and dries but I am sure it has room for improvement.  Unfortunately, there is no quick way to determine longevity.   

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