Plein air painter Beth Bathe answers five reader questions about how to use water-mixable oils. 

Plein air painter Beth Bathe
Plein air painter Beth Bathe

Q: What product should I use to glaze with water-mixable oils?
~ Sally Pym, Venice, FL

Water-mixable mediums have been developed for water-mixable oils — quick dry mediums, stand oils, painting mediums, impasto mediums, linseed oils, alkyd mediums, and glazing mediums.

Water-mixable oils can also be mixed with any traditional oil, and if you use it in a 2:1 ratio — two parts water-mixable and one part traditional oil — the paint will maintain its water-mixability.

Q: Oils can be used in winter, but what about water-mixable oils? Are there temperatures at which using them is a challenge?
~ Ken Shipman, via Facebook

Yes, painting in temperatures close to freezing can be challenging when using water as a medium, especially in the early, thin wash stages. The water on your palette can actually freeze and resemble slush or acquire a gritty feel. The water-mixable paints themselves have no water in them, so the paint directly out of the tube will not freeze. I have been told that some painters put a bit of alcohol in their water to prevent it from freezing. Water-mixable paints will also not work as well in the rain. Although it can create some interesting textural effects, it can also wash away your painting.

Q: How does the working time of water-mixable oils compare with that of traditional oils?
~ Greysun Conroy, via Facebook

Depending on how thick you paint, water-mixable oils retain their elasticity and workability for up to 48 hours. Like traditional oils, water-mixables must dry through oxidation — the absorption of oxygen through the air. Once dry, they are just like any other oil painting and should be treated as such. Like traditional oils, water-mixable oil paintings cannot be reactivated with water when dry.

Q: Can water-mixable oils be used over an oil painting that has dried for over a year? If so, what is the process?
~ Linda Nicholls, Hunter, NY

I use Cobra paints, which do allow you to paint over an older painting that has dried; you just won’t be able to use water as a solvent. Instead, use one of the Cobra mediums to give it a “wake up” — the technical term is oiling out. Begin by removing all the dust and grime with a damp cloth and allow the paint-ing to dry completely. Then apply a thin coat of oil medium and allow it stand for at least a day (choose a location where it’s not going to gather dust). At that point, you should be set to begin painting again.

Q: Is it safe, archivally speaking, to put a palette of water-mixable oils in the freezer in between painting sessions to keep them workable so they do not dry out and I don’t waste paint?
~ Julie Hunt, Alberta, Canada

Yes, I have found that my water-mixable oils can be put in the freezer for storage. There is no water in the paint, only pigment, linseed oil, and the emulsifier.

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