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Old 11-20-2009, 06:02 PM
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gunzorro gunzorro is offline
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Oils Yellowing

These are the first stage of results comparing the yellowing characteristics of various oils.

These samples have been exposed to four different types of light for approximately seven months.

Top to bottom:
1) direct sunlight/open shade
2) diffuse window light (small) and direct sun (15 min/day)
3) typical interior office (diffuse daylight/fluorescent lighting)
4) dark drawer

Oils used (l to r):
linseed
sun-thickened linseed
walnut alkyd (late addition)
stand oil
walnut
safflower
poppy

The outdoor sample shows wind-blown debris attached to the walnut, safflower and poppy sections. These oils remained slightly sticky in the direct sun, when the linseed-based on the left remained harder. Oils were only partially cured before being placed in the direct sun.

As expected the sun bleached the outdoor sample, and the sample kept in a drawer was the most yellow. The samples are now all in the outdoor sunlight, and will be photographed again in a few days. (The stand oil pooled into a thick center layer that looks yellow, but the outer side are more accurate for comparison.)



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Old 11-20-2009, 07:14 PM
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Brian Firth Brian Firth is offline
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Re: Oils Yellowing

Great post Jim. Looks like the safflower and walnut yellowed less than the poppy, which is interesting, considering many think poppy is superior, just because it it more expensive. Do you mind posting what brands of oils you used?
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Old 11-20-2009, 07:26 PM
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Re: Oils Yellowing

Thanks a lot Jim, like Brian I am surprised about the poppy, it is really not supposed to do that given it's fatty acid profile and well known reputation for not yellowing. I have never done a poppy oil test. I am also getting some tests ready to post in a few days, nice work.

Last edited by sidbledsoe : 11-20-2009 at 07:31 PM.
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Old 11-20-2009, 08:20 PM
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Re: Oils Yellowing

Very interesting, Jim, thanks for posting this.
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Old 11-20-2009, 08:37 PM
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Re: Oils Yellowing

In the event of a lottery win, I've mentally crossed Blockx off my list of desirable brands. Very surprising result with the poppy oil. I'm glad I use walnut and walnut alkyd.

I intend to buy some stand oil for a particular project, following advice on another thread, so I'm glad to see the yellowing is not too pronounced. Thanks for providing this information.
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Old 11-21-2009, 12:38 AM
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Re: Oils Yellowing

I was surprised by the poppy as well. But keep in mind, this is ONE older jar of Talens poppy oil, and I've no idea on its processing. Also, not that with even the mildest light in the garage (2nd from bottom), the poppy is clear. I would certainly not use this one example as a reason to avoid poppy oil. But it is a good comparison on the relative yellowing -- the linseeds are far worse, as is the Graham Walnut Alkyd. Nothing surprising here, really -- if you want to keep oils at their lightest, don't store paintings in a drawer or closest!

These are double coats of oil, with some visible beading on the linseed second coat. The first coat was mostly absorbed by the canvas/primer, so after thorough drying, I added the second coat.

Let's see how it all looks after a couple days in the sun.

Brian -- Sure, I'll take a photo of all the types of oils I used when I re-shoot the panel from sun-bleaching.
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Old 11-21-2009, 03:01 AM
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Re: Oils Yellowing

I agree and would not jump to conclusions about poppy in general that fast.
Due to that result, I am suspicious of the addition of driers to that particular poppy oil, a drying rate test alongside of linseed, walnut, and safflower oil may help, poppy should be similar to safflower providing no driers present.
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Old 11-21-2009, 07:18 AM
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Re: Oils Yellowing

Thanks Guns.....Now I'm concerned...I use Poppy oil a lot
in my paintings....tnx...I'll stay tuned here.....art
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Old 11-21-2009, 12:48 PM
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Re: Oils Yellowing

Quote:
Originally Posted by gunzorro
I was surprised by the poppy as well. But keep in mind, this is ONE older jar of Talens poppy oil, and I've no idea on its processing. Also, not that with even the mildest light in the garage (2nd from bottom), the poppy is clear. I would certainly not use this one example as a reason to avoid poppy oil. But it is a good comparison on the relative yellowing -- the linseeds are far worse, as is the Graham Walnut Alkyd. Nothing surprising here, really -- if you want to keep oils at their lightest, don't store paintings in a drawer or closest!

I take your point about the poppy oil, but I live in a dark house, in a part of the country with an especially cloudy, rainy climate (even by British standards!), so I'll still give the poppy a miss. Its rising cost is another good reason. I use more of the walnut oil than the alkyd, and also safflower oil, so I should be ok.
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Old 11-22-2009, 09:04 AM
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Re: Oils Yellowing

An excellent work of research, a guarantee of results!

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Old 11-24-2009, 02:49 PM
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Re: Oils Yellowing

hey im just wondering about this.. would the same oil yellow as much on glass or tiles.. maybe the interaction with the gesso/chalk and canvas fibers had an effect on the acid in the oil? like newspaper yellows
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Old 11-24-2009, 03:19 PM
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Re: Oils Yellowing

refract -- The yellowing will take place on any surface. I use acrylic-primed polyester, so no, there isn't any interaction going on here. A second coat of oil was applied of the first, so the second is isolated from the surface and still yellowing. The yellowing is part of the nature of drying oils (some, like linseed, more than others).
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Old 11-24-2009, 03:49 PM
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Re: Oils Yellowing

Here is a strip of mine with walnut oil and linseed oil shown with the typical yellowing that occurs in the dark, followed by the same strip exposed to light for a couple of days:


remember that these are straight oil not mixed with paint but I have done tests with paint and you see similar results. I've used linseed based paint in painting for many years with no yellowing problem.

Last edited by sidbledsoe : 11-24-2009 at 03:54 PM.
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Old 11-27-2009, 03:38 PM
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Re: Oils Yellowing

Following 3 days of sun-bleaching:



Still, not perfect, especially in the Sun-thickened Linseed (second from left). All the linseed-based have some yellowing evident, but a huge improvement overall.



The poppy oil on the right is quite old and has yellowed a bit. I'm sure more recent samples would remain more clear. But in the above photo of the samples after exposure to sun, the yellowing is eliminated. In other words, no need for concern about poppy oil yellowing.

Last edited by gunzorro : 11-27-2009 at 04:09 PM.
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Old 11-28-2009, 09:08 AM
Mathieu1980 Mathieu1980 is offline
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Re: Oils Yellowing

Hi,

short intro:
I'm not really new here, been secretly spying on this forum . I've never finished a painting yet. All my canvas panels I painted on are being recycled into color charts at this moment.


Thank you gunzorro, for sharing all these (and other) tests with us!
What I didn't know and surprised me a lot is that after the oil is cured, just a short time in the sun will significantly reduce the yellowing of the oil ???
It can still change after it's cured?
Will it yellow again if you put it back in a dark place for a while?

The safflower is doing a great job from what I can tell. I'll have to search for more info about it, to see if there are any negative properties as well.

Thanks!
Mathieu

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