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Berl Mendenhall

Cooking Colophony Down For Color, Low and Slow?

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Hi Daniel, I'll see if I can get a reprint from  a scientific library nearby. Should have an interesting bibliography.

 

 

Is there a reason the Chemical post can't be opened?

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In this 1953 paper the experiments were performed in a nitrogen atmosphere to reduce oxidation, so the relevance to most home-brew varnish-making is likely to be limited.

 

However, there are a few interesting tidbits:

> When heated to different temps, biphasic changes occur in the rosin that appear to have a transition at around 250C

> Crystallisation is reduced when rosin is cooked at higher temps (>250C).  Perhaps this has some relevance to 'chippiness' of a varnish.

> From the text: "At temps >250C the color bodies produced by oxidation were apparently decomposed."

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In this 1953 paper the experiments were performed in a nitrogen atmosphere to reduce oxidation, so the relevance to most home-brew varnish-making is likely to be limited..

> From the text: "At temps >250C the color bodies produced by oxidation were apparently decomposed."

 

Decomposed color bodies means that the rosin became more colorless with hotter/longer cooking... in the absence of oxygen.  Which implies that oxygen is necessary for color, and perhaps a drying oil scavenging the oxygen could result in loss of color when the varnish dries.

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Great photo. Seems you really pushed the boundaries. Personally I don't think I would use the extremely dark ones in a varnish...don't know why exactly,...I wonder if a good varnish can be made from charred rosin?

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Don't forget: These films on the sticks are thick; combined with oil into a varnish and applied in thinner films may result in a very desirable color.

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White spruce is ideal rosin for cooking. I don't think that the people who purify this raw material dissolve it in anything but turpentine. I would google around and find the manufacturing methods for this. If nothing is found, I would warm it with some quality turps from Diamond G and pass it through a wire mesh to collect the large pieces. Then maybe in a liquid state, the detritus would settle to the bottom or top and then can be decanted. I would keep the temperature low so as to not carbonize the twigs and needles. Again, I urge you to google around and find an answer.

I found a lot of links to purifying pine sap.

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Around 160C this is the best varnish I have made to date, it’s a dark red brown, it dries quickly and is beautifully transparent.

 

I will post a pic of a test piece. Soon 

 

55%oil to resin. 

 

This is is pretty similar to the Hargreaves recipie 

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6 hours ago, lpr5184 said:

Great photo. Seems you really pushed the boundaries. Personally I don't think I would use the extremely dark ones in a varnish...don't know why exactly,...I wonder if a good varnish can be made from charred rosin?

It’s great to have such a dark varnish, less pigments and  you can easily lighten it by mixing in a lighter varnish 

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16 hours ago, finnfinnviolin said:

One hundred hours , in case anyone wants to see what that looks like, I actually cooked it for 170 hrs, but it pretty much looked black after 100 

623E9CDE-51A8-465F-A96A-4478FB6B766F.jpeg

Is the 100 hr mark in between 5 and 6?

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Not to steer the topic but something I found to be interesting I tapped several big larch trees which I have in abundance here in North Idaho and found using a copper pipe for a spout does funny things . I drilled a 3/4 “ hole 6” into the tree to put the pipe into and hung this bottle on the end . It’s the greenest stuff you can imagine . I’ve cooked larch sap before and want to do more testing with it . 

787104D9-56A2-468B-AE4B-B7D703F1B532.jpeg

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22 minutes ago, finnfinnviolin said:

Here’s a test, three coats with my fingers 

B11A4F5A-FBF1-4BBB-9704-EA68D2C8F331.jpeg

Not bad at all... although your wood looks pretty dark to begin with. Can you elaborate on what you used to darken and perhaps show a photo of the bare wood?

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1 hour ago, Edward Byler said:

Not to steer the topic but something I found to be interesting I tapped several big larch trees which I have in abundance here in North Idaho and found using a copper pipe for a spout does funny things . I drilled a 3/4 “ hole 6” into the tree to put the pipe into and hung this bottle on the end . It’s the greenest stuff you can imagine . I’ve cooked larch sap before and want to do more testing with it . 

787104D9-56A2-468B-AE4B-B7D703F1B532.jpeg

copper compounds do tend to that color

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how many hours is the one in the middle?  Thats a big change from the ones on the left and then not much change until the end.  

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1 hour ago, lpr5184 said:

Not bad at all... although your wood looks pretty dark to begin with. Can you elaborate on what you used to darken and perhaps show a photo of the bare wood?

Ground is UV, nitrite, then egg white, mixed with some saffron tincture.

 

followed by oil varnish burnished with glass powder, don’t have any pics right now 

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12 hours ago, Michael_Molnar said:

White spruce is ideal rosin for cooking. I don't think that the people who purify this raw material dissolve it in anything but turpentine. I would google around and find the manufacturing methods for this. If nothing is found, I would warm it with some quality turps from Diamond G and pass it through a wire mesh to collect the large pieces. Then maybe in a liquid state, the detritus would settle to the bottom or top and then can be decanted. I would keep the temperature low so as to not carbonize the twigs and needles. Again, I urge you to google around and find an answer.

I found a lot of links to purifying pine sap.

Alcohol also dissolves almost all of white spruce resin. The alcohol can be cooked off after decanting and filtering. I made some clear varnish years ago by boiling off the alcohol in linseed oil; the resin combined with the oil readily when the alcohol was gone and the oil was hot enough.

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