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Michael_Molnar

Cooked Rosin is Fugitive

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5 hours ago, DonLeister said:

Jim, what is the ratio of oil to resin? And is that all the varnish ingredients?

Don, the ratio is 1:1.  The varnish by weight is 50% rosin, 5% mastic tears, and 45% linseed oil.  Then the color is added (50% linseed oil and 50% cooked rosin) at twice the quantity used for the varnish.

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If I understand correctly you cook a varnish , 50:45:5 , which is not very dark. Mastic added at the end of the cook at a lower heat than the rosin/ oil cook.

To that you  make 50:50 raw oil and very well cooked rosin ( mulled together ?). That basically looks like black paint right?

Then you add that 2 parts to 1 part previously cooked varnish. And  it is added under heat at 100c., right ?

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18 minutes ago, DonLeister said:

If I understand correctly you cook a varnish , 50:45:5 , which is not very dark. Mastic added at the end of the cook at a lower heat than the rosin/ oil cook.

To that you  make 50:50 raw oil and very well cooked rosin ( mulled together ?). That basically looks like black paint right?

Then you add that 2 parts to 1 part previously cooked varnish. And  it is added under heat at 100c., right ?

Yes.  Instead of mulling (how Joe T. does it), I melt the cooked rosin into the oil at 200 C then combine as soon as the temperature drops under 100 C.  Joe says he used to do it this way, but mulling is faster and reaches the same result.  I melt first so that I can pass it through a metal coffee filter as I combine the two parts.  Probably an unnecessary step.

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@Michael_Molnar

I always thought the main purpose of cooking colophany is to make it dry faster and not for color. (At least I can't remember that old recipes say that cooking is made for the purpose of color. But many recipes say at the end that a cooked varnish dries fast.)

For color there are makers who simply add stuff which contains carbohydrates, so either some gums (which actually distinguishes them from resins) or pure sugar will do it too. 

I think Christoph Götting spend something like 20 years of his life to find a method to boil rosin in s way that it becomes a really nice red. (Don't ask me if this is done with or without Linseed oil or if any tricks are applied, Christoph Götting is not talking about anything) I have seen long ago his varnish on an instrument where he copied a Venetian maker (I think it was a Montagnana violin) and it looked very, very convincing. 

IMO to make a nice color varnish you MUST blend varnish and pigments. The trick there seems to be combining their right colors and getting the density of pigments in the matrix just right.

I stopped cooking varnish because in Central Tokyo you will be soon on the black list of the fire department for disturbing your neighbors with smoke and secondly I got a bit frustrated in making always brown stuff.

On we go (seems nowadays the motto for varnish makers not giving up to reach a goal no mortal can reach):D

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7 minutes ago, Andreas Preuss said:

@Michael_Molnar

I always thought the main purpose of cooking colophany is to make it dry faster and not for color. 

For color there are makers who simply add stuff which contains carbohydrates, so either some gums (which actually distinguishes them from resins) or pure sugar will do it too. 

I think Christoph Götting spend something like 20 years of his life to find a method to boil rosin in s way that it becomes a really nice red. (Don't ask me if this is done with or without Linseed oil or if any tricks are applied, Christoph Götting is not talking about anything) I have seen long ago his varnish on an instrument where he copied a Venetian maker (I think it was a Montagnana violin) and it looked very, very convincing. 

IMO to make a nice color varnish you MUST blend varnish and pigments. The trick there seems to be combining their right colors and getting the density of pigments in the matrix just right.

I stopped cooking varnish because in Central Tokyo you will be soon on the black list of the fire department for disturbing your neighbors with smoke and secondly I got a bit frustrated in making always brown stuff.

On we go (seems nowadays the motto for varnish makers not giving up to reach a goal no mortal can reach):D

Are you sure Gotting's resin was rosin and not fir resin?

 

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Thanks Jim. 

Just to be sure of your process, you melt the darkened rosin with oil at 200c then add that to the first cook of rosin and oil (which is not nearly as dark).  And the first cook is hot when you add the dark rosin oil cook?               

If I have that right, when your final varnish cools and is too thick, you then thin it with raw oil?  

 

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3 hours ago, Andreas Preuss said:

IMO to make a nice color varnish you MUST blend varnish and pigments. The trick there seems to be combining their right colors and getting the density of pigments in the matrix just right.

I too have reached the same conclusion... with the possible exception of iron rosinate, which seems to give a more reddish brown than any other.  You could argue that the iron actually forms a pigment when the varnish dries, and you'd probably be right.

I recently re-cooked a collection of varnishes and came out with stuff that looks fantastic in the jar...

IMG_2036.JPG.748358e0b1386ad5b702034b9cdad12b.JPG

... but in normal varnishing thickness, it's just a pale yellow (#10 sample below)  I don't know if it fades in UV.   #23 is iron rosinate varnish; useful I think, but it's just one color.  At least it doesn't fade.

IMG_2035.JPG.31e184c10c8bb5099378d8d61dea1c74.JPG

 

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6 hours ago, DonLeister said:

Thanks Jim. 

Just to be sure of your process, you melt the darkened rosin with oil at 200c then add that to the first cook of rosin and oil (which is not nearly as dark).  And the first cook is hot when you add the dark rosin oil cook?               

If I have that right, when your final varnish cools and is too thick, you then thin it with raw oil?  

 

Yes that's it.  I take samples during the cook and add a little (a few milliliters) LO if I think the viscosity is too thick for my application method.  I haven't tried adding raw oil cold to the finished varnish.  Joe T. thinned some of Bill's varnish that ws too thick by adding LO to the varnish after heating it up, but I don't know the details of how he did it.

-Jim

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4 hours ago, Don Noon said:

I too have reached the same conclusion... with the possible exception of iron rosinate, which seems to give a more reddish brown than any other.  You could argue that the iron actually forms a pigment when the varnish dries, and you'd probably be right.

I recently re-cooked a collection of varnishes and came out with stuff that looks fantastic in the jar...

IMG_2036.JPG.748358e0b1386ad5b702034b9cdad12b.JPG

... but in normal varnishing thickness, it's just a pale yellow (#10 sample below)  I don't know if it fades in UV.   #23 is iron rosinate varnish; useful I think, but it's just one color.  At least it doesn't fade.

IMG_2035.JPG.31e184c10c8bb5099378d8d61dea1c74.JPG

 

No 10 definitely looks too light to be used alone. You might try to add sugar. I haven't done that but if you search on the net there is a guy who has put out some information on the net. It's certainly not too complicated to make, but you can see s

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Jim, thanks. 

We are doing the same thing pretty much then. The only difference is I add my dark rosin in powder form directly into the first cook, (sprinkle it in slowly) instead of blending it with oil first. it dissolves completely into the varnish. It can make a very dark and thick varnish so it needs some oil added at the end of the cook.

I tried mulling the dark powdered rosin in oil like Joe's but mine wouldn't dissolve into the varnish cook. I mulled it in raw oil and left it for a day (sealed) and it basically dried like rubber almost.

I think I might try your way of melting oil into the dark rosin at the end of it's cook. Is that how you did it? While the dark rosin is still hot?

I know after I have cooked the rosin down to darken it, I can't get it out of the pot before it hardens mostly so I scrape it out after it cools. It's very brittle. It looks like it is burnt but it will completely dissolve in acetone or hot varnish.

 

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9 minutes ago, DonLeister said:

 

I think I might try your way of melting oil into the dark rosin at the end of it's cook. Is that how you did it? While the dark rosin is still hot?

 

I think that’s right, but words are sometimes a hindrance to communication. Sometimes I think we (people) are better off pointing with well timed grunts. :)   Here’s a picture for me to “point and grunt” at.  
 

The beaker on the right has 1:1 cooked rosin melted into LO (the color).  In the pic. the color is cooling down from 200 C. I only had it at that temperature long enough to be all liquid.  When the temperature drops to 100C I will combine it with the varnish in the beaker on the left that has the varnish holding at 100 C in a sand bath. I let them combine for 30 minutes before filtering into the small jar on the left (also in the pot). I preheat the final jar so that I can filter the finished varnish directly into its storage jar while hot.  
 

1285AC21-1732-48FD-96C8-3AC2FC262CD6.jpeg.c3c52bdf3d637463d395450e86b23b5a.jpeg

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Jim I think your sample looks good. Of course what goes under it will make a difference like you say.

From reading Hargrave's recipe for making varnish I was always left with the impression that his long slow resin cook is the resin component of the whole varnish. In other words he is not adding the darkened resin to an already made varnish.  I just now realized that he was adding this dark resin to the already made 'boring' varnish that he described earlier. And that is how Joe taught us. 

 

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23 hours ago, Andreas Preuss said:

On we go (seems nowadays the motto for varnish makers not giving up to reach a goal no mortal can reach):D

It's also a nice (not rude) double entendre.

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12 hours ago, Andreas Preuss said:

Of course I don't know what sort of  resins he is cooking.:rolleyes:

all secret.

Last time i corresponded with him  (Gotting)he was using some sort of resinates,that was quite a while back though and he still has the same photos on his site as back then.

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40 minutes ago, fiddlecollector said:

Last time i corresponded with him  (Gotting)he was using some sort of resinates,that was quite a while back though and he still has the same photos on his site as back then.

I met Christoph Gätting two or three times. He is a really nice guy but when it comes to varnish recipes he politely stays silent. 

The only thing I know from my colleagues who know him better than I do is that he arrived already a couple of times at the ultimate solution just to be back at the cooking pot the next day. I think varnish making is a sort of addiction to him. (I can understand that:D)

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15 hours ago, Melvin Goldsmith said:

You don't need pigments...if you use them for my varnish a tiny addition will make a big difference...pic is all cooked in colour

56770556_10157130423369334_6609170008083791872_n.jpg

Fully agree now, would not have agreed three years ago :)

It's unbelievable until you have cooked such varnish

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On 10/23/2019 at 7:01 PM, Ernest Martel said:

Once the oil reaches "sweet meats" will it still dry on it's own? ...and can it still be crosslinked and made into a varnish?,...or should you discard it?

How long does it take linseed to reach that stage?

Sweet meats require some complex cooking....I'll try to find the recipe.

However like stand oil it is fully polemerized without being oxidized....rendering it useless for our purposes.

 

on we go,

Joe

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So, the evidence is that cooked (oxidized) rosin must be carefully integrated to varnish to retain its color. This is what I suspected in starting this thread.

I did not realize that Thrift and Hargrave were adding cold oxidized rosin to enhance color much like a lake.

I have more work to do on this.

Thanks to all.

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Mike,  I might not say ‘cold’ but precooked to the point that it is more of a pigment than a resin. Although it doesn’t behave like a pigment because it will fully dissolve  in hot varnish or hot rosin or acetone. I dunno what you would call it in a technical sense

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2 hours ago, DonLeister said:

Mike,  I might not say ‘cold’ but precooked to the point that it is more of a pigment than a resin. Although it doesn’t behave like a pigment because it will fully dissolve  in hot varnish or hot rosin or acetone. I dunno what you would call it in a technical sense

Agreed. Thanks, again.

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