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artasart
10-25-2012, 06:41 PM
Hi all,
I am doing some projects (painting on wood) using emulsions where accelerating the yellowing of linseed oil - due to the presence of casein (which I am using already for this purpose) or due to any other agent - is beneficial. Can anyone tell me what causes the yellowing of linseed oil?
What the casein is doing to the linseed oil?
What are any other known substances usually avoided to prevent the yellowing of linseed oil which I might use to bring it on?
I know that yellowing is usually something to be avoided but in my case, if I could understand a bit better what causes it, my project will be rendered more beautiful by causing more of it!
Thanks for your comments.
Cheers,
Art

Trond
10-25-2012, 09:34 PM
I don't know about casein, but could it be because it is aqueous?

Darkness and dampness are the things I know about that cause yellowing of linseed oil. Light and relatively dry environment will bleach away the yellowing. Probably lots of fresh air helps too, for those who want to avoid yellowing.

sidbledsoe
10-25-2012, 10:05 PM
Hi all,
I am doing some projects (painting on wood) using emulsions where accelerating the yellowing of linseed oil - due to the presence of casein (which I am using already for this purpose) or due to any other agent - is beneficial. Can anyone tell me what causes the yellowing of linseed oil?
What the casein is doing to the linseed oil?
What are any other known substances usually avoided to prevent the yellowing of linseed oil which I might use to bring it on?
I know that yellowing is usually something to be avoided but in my case, if I could understand a bit better what causes it, my project will be rendered more beautiful by causing more of it!
Thanks for your comments.
Cheers,
Art
The yellowing of Linseed oil is caused when conjugated unsaturated hydroperoxides are converted into conjugated unsaturated ketones. These unsaturated ketones can produce long-chain coloured polyenes. Siccatives can also contribute to discoloration and/or yellowing.
Hope this helps!:D

!becca
10-25-2012, 10:16 PM
The yellowing of Linseed oil is caused when conjugated unsaturated hydroperoxides are converted into conjugated unsaturated ketones. These unsaturated ketones can produce long-chain coloured polyenes. Siccatives can also contribute to discoloration and/or yellowing.
Hope this helps!:D
I always have known to watch out for those ketones..it helps me..:D

Ron Francis
10-25-2012, 10:17 PM
I don't know why linseed turns yellow but I think it has something to do with the lignan in it.
Regardless, I don't think there is any way of effectively speeding it up the yellowing.
That is, if you leave it in a dark place, it will go yellow more quickly, but returning it to a light place will bleach the yellow again.
Maybe artificial ageing with heat, but I don't know much about that at all.

Possibly you would be better off simulating the age with orange/yellow glazes?

sidbledsoe
10-26-2012, 08:26 AM
I have never read that lignans played a part in the yellowing phenomenon that occurs upon polymerization. I have read that they do contribute to the natural coloration of linseed oil. The subsequent yellowing upon drying is a separate coloration produced than the original amber/yellow color of the liquid oil. The higher the linolenic acid content, the more a drying oil will exhibit yellowing (upon drying) so perilla oil (http://en.wikipedia.org/wiki/Perilla_oil)yellows more than linseed. Now I am guessing but I would think that the longer chain fatty acids like linolenic will produce more co-oxidation reactions that I mentioned in the first post, that lead to formation of more colored polyenes.
Drying without light in a humid environment will cause faster yellowing.
What the casein is doing to the linseed oil? I didn't know about casein enhancing the yellowing, this is the first I have heard of that, but if you say it does then go for it.
I always have known to watch out for those ketones..it helps me..
becc, then stay sober, in alcoholic ketoacidosis, alcohol causes dehydration and blocks the first step of gluconeogenesis. The body is unable to synthesize enough glucose to meet its needs, thus creating an energy crisis resulting in fatty acid metabolism, and ketone body formation.

!becca
10-26-2012, 08:45 AM
becc, then stay sober, in alcoholic ketoacidosis, alcohol causes dehydration and blocks the first step of gluconeogenesis. The body is unable to synthesize enough glucose to meet its needs, thus creating an energy crisis resulting in fatty acid metabolism, and ketone body formation.;) :angel: this is true, ketoacidosis can also occur with kwishiorquor..and it is reversible with improved diet..it is also observed with anorexia..

I have been friend tending lately...it is tough..but I am staying in safe limits..;)

(Sid, good luck with any weather your way, stay safe and dry)

Ron Francis
10-26-2012, 09:48 PM
Sid,
Either I'm going crazy, or your post wasn't there when I posted mine.
Had I seen it, I wouldn't have said anything about lignan.

!becca
10-26-2012, 10:12 PM
Either I'm going crazy:angel:

sidbledsoe
10-26-2012, 11:11 PM
no prob at all Ron, it is all good to know, I had to look up lignans and see what they were doing myself, apparently the health food people really dig them and want their linseed to have lots of it!

Ron Francis
10-26-2012, 11:53 PM
Becca!!

!becca
10-27-2012, 01:39 AM
Becca!!:D :wave:

wetbob
10-27-2012, 04:52 AM
thnx sid, ketones, fatty acid metabolism, conjugated unsaturated hydroperoxides, conjugated unsaturated ketones, long-chain coloured polyenes....?

sidbledsoe
10-27-2012, 06:32 AM
What are any other known substances usually avoided to prevent the yellowing of linseed oil which I might use to bring it on?
I know that yellowing is usually something to be avoided but in my case, if I could understand a bit better what causes it, my project will be rendered more beautiful by causing more of it!
Thanks for your comments.
Cheers,
Art
Art, in other words, there are profound reactions that slowly happen that cause the yellowing, as I suggested, driers will exacerbate the darkening/yellowing so what I would do if I were you that is really quick, easy, and cheap would be to head straight for the hardware store and get some boiled linseed oil. Ditch the good artists crap and slather that cheap hardware stuff on.
It is still called boiled linseed, but it is not really boiled now, it used to be in the old days. It is made to be fast drying. But heating is an expensive alternative, a cheap method is to just add driers to linseed. These both speed the drying and in the process, make it yellow moreso.

!becca
10-27-2012, 08:17 AM
Art be sure to post this creation at it's conception and yellowed best.

sidbledsoe
10-27-2012, 01:06 PM
yes, I absolutely love having been able to give the advice for once in my life that you should ditch the artists grade stuff and use what is more appropriate, the hardware grade stuff!:D

Gigalot
10-27-2012, 02:41 PM
Damar varnish and Alkyd varnish addition reduce yellowing.
(Acidic additives reduce yellowing while Basic additives like sodium tetraborate in casein glue increase yellowing process?)

!becca
10-27-2012, 03:02 PM
yes, I absolutely love having been able to give the advice for once in my life that you should ditch the artists grade stuff and use what is more appropriate, the hardware grade stuff!:D
It is kind of special.;)

Gigalot
10-29-2012, 06:27 AM
Grocery grade oils are less yellowish :lol:

karenlee
10-29-2012, 10:03 AM
I don't see the problem in using a transparent yellow pigment instead of whatever Sid said. Please explain.

!becca
10-29-2012, 10:39 AM
Grocery grade oils are less yellowish :lol:
lol...my olive oil is a beautiful amber..:D

Karen, I think the yellow of oil is difficult to duplicate with pigment..

And, btw, I think there are antiquing mediums that r available that could be added...

karenlee
10-29-2012, 11:59 AM
With all due respect, I do not believe that duplicating the yellow of oil with pigment is so difficult that one could not do it. We have a painter around here who went through a period of painting stuff that looked several hundred years old--he was quite successful in achieving that yellowed look. I will post some when I remember his name.

!becca
10-29-2012, 12:07 PM
Karen, I think it can be done, but not as effectively or easily as modifying the medium...I think I would use one of these products (http://www.dickblick.com/categories/varnishes/antiquingvarnishes/details/)

Gigalot
10-29-2012, 01:14 PM
lol...my olive oil is a beautiful amber..:D

Karen, I think the yellow of oil is difficult to duplicate with pigment..


You bought a Becca`s grade oil! :D

Rosin, heated with linseed oil has deep amber color. Dragon tree sap..

But Blockx 148$ amber varnish bottle has an unbeatable design! :clap:

!becca
10-29-2012, 01:31 PM
Only the best oil for me..;)

Bottle design is of great importance with such purchases..:D