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Mhurocy
03-21-2019, 11:38 PM
I am wondering if a 50/50 mix of linseed and walnut oil mixed into my paints that are kept on the palette (closeable easle companion) would be a good idea. Right now I am only using walnut oil, and my paints have stayed very fresh on the palette for several days, but I am concerned about the rancid issues with walnut oil, and how would this mix effect the fat over lean rule? As of now I am doing a 50/50 mix of odorless mineral spirits and galkyd for my underpaintings, and blocking in, but with a healthy amount of oil already mixed in with my paints, do I need to worry about fat over lean? I am assuming, not to worry about additional oils at this point since there is already oils added to my paints. Is it a good practice to pre-mix additional oils to start?

Thanks!

Miklos

piston_pounder
03-22-2019, 05:00 AM
From what I can understand of your question is you are wondering if you need to increase your oil ratio of your paint going on top of the galkyd layer.
I am a fairly new painter but I too have been trying to find the best oil medium for my slow drying needs. If you stick to what seems to be the fat over lean rule, you will need to add more oil to the subsequent layers. It doesn't need to be much at all, just needs to be more. Just make sure no galkyd goes over top the oily layers as it will trap any gases that occur during the curing process of the oils below, causing the paint to delaminate (this is what I have read to understand)

I currently have a post awaiting a solid answer on the technical forum directly below this post asking about mixing walnut and stand oil. For me, I just want a slow drying medium that will last about a week before curing begins. For you, adding linseed won't change whether or not the walnut oil will go rancid as far as I know, it will just slightly decrease drying time since it dries slightly quicker than walnut oil alone. But this was where I was wondering if its OK to mix the two because I don't know if the linseed oil will start to dry before the walnut oil when they are mixed, causing some weird curdled mixture of oil that half wants to dry and half wants to stay wet... if that makes sense?

If you really want to make sure the oils in your pre mixed containers stay fresh and wet for long, add a drop of clove oil to the container and store it in the freezer when not in use. Clove oil is just an alcohol base so it evaporates completely over time. It is the clove fumes that retard the oxidizing process of the oil. From what I understand, there is no problem at all with pre mixing oil and medium as long as it is stored in an airtight container. If the only air in the
container is saturated with clove fumes, the paint is essentially preserved in the container.

I hope that helps, I am fairly new but i have been researching like mad. If someone sees an error in my advice please correct me but I am fairly confident of my info.

Delofasht
03-22-2019, 10:33 AM
Rancidity only matters in the context of flavor... it has no effect on a paint film. The effect noticeable is that by the nose, the off gassing of the oil. Often at that point you may not enjoy the taste of the oil anymore, but since we are painting here and not cooking dinner, I think that is probably fine (rule number one: donít eat your paint).

In general, the rules for mediums is to either use more in each layer, or about the same amount in each layer.

Pinguino
03-22-2019, 11:27 AM
To expand upon what Delofasht wrote above: The "drying" process for oils involves molecular bonds being broken and re-joined in a different configuration. Sometimes, small pieces are chopped away, and these pieces can slowly evaporate from the oil. They have a detectable odor, which we call "rancid." But the oil is still good for painting.

Oils that do not "dry" also do not go "rancid," unless there are non-oil ingredients that spoil. So, ordinary butter will go rancid at room temperature, because the non-fat component degrades. But butter can be rendered to a purified fat known as "ghee," which is free of non-fat components, and can be kept at room temperature for a long time.

But regarding the original question: If you store your palette in the fridge when it's not being used, the paints will last longer before they become unworkable. Freezer also works, as long as there's not water involved.

DAK723
03-22-2019, 04:00 PM
If you are adding walnut oil to your paints as a medium I see no reason to also add in linseed oil.

Don

Ted Bunker
03-22-2019, 04:21 PM
It's commonly referred-to as "drying", but think of your oil paints curing when exposed to the air instead. The oil binder really doesn't evaporate, it slowly bonds and links to itself at the molecular-level to form a solid layer of "paint". Cold temperatures slow-down the process; just as submerging the paint in water or wrapping it in plastic robs it of oxygen needed to cure. Clove or lavender spike oil fumes trapped in a sealed palette also retards the curing.

Some pigments retard this curing, while others like burnt umber accelerate the process as they contain natural "driers" like manganese.

contumacious
03-22-2019, 04:27 PM
If you are adding walnut oil to your paints as a medium I see no reason to also add in linseed oil.

Don

I agree with Don on this. The walnut oil would be my choice as it tends to slow drying time.

Mhurocy
03-22-2019, 07:25 PM
Makes sense to me, thanks!

C_Verdun
03-24-2019, 11:00 AM
I agree, rancidity of oil paints is of no concern for oil painters. It just means it's drying. I like to work some of my abstract paintings even after they are partially dried. As legend has it, Rembrandt used to push and pull his half-dried paint on his paintings like it was taffy.

As to the original question, I have tried to preserve paint on my palette with several ideas:
storage in the freezer (you have to be careful of condensation)
clove oil (a powerful antioxidant!)
carbon dioxide (displaces oxygen)

It is a very difficult proposition to retain oil paint over any substantial amount of time as it doesn't take very much oxygen to cause hardening, or at least "skinning of the surface. Nowadays, I don't worry about it so much.