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Alternatives to OMS to thin underpainting/drawing?

(Geoff) #1

Hi all,

I don’t care for odorless mineral spirits (or turpentine); my studio is not as well-ventilated as I would like, and I worry about inhaling the stuff. So I simply use M. Graham walnut oil as a medium, to clean brushes between strokes, and to clean up after painting. Walnut oil is great – except that it’s not really appropriate for thinning paint for an underpainting or sketch, as ideally one wants that first layer to be “lean,” not “fat,” and oils are “fat.”

The traditional answer is to thin the drawing (or first layer of an underpainting) with OMS or turpentine, but those aren’t an option for me. Paint out of the tube works okay, but it doesn’t dry fast enough, and it pollutes or show through later layers. A thin layer of water-miscible oils, thinned with water, is a conceivable solution for a drawing/underpainting, as is a layer of water-thinned acrylics or even water-thinned casein. Drawing lightly with a light or gray colored (wax or oil, not graphite) pencil is my current approach. But I’m wondering there are any other solutions. Anyone have suggestions?

Thanks in advance!

(Anne Wood) #2

Hello Geoffrey,

Have you tried using a little alkyd medium with some transparent oil colour? It helps to dry quickly and scrubbed onto the canvas or board will make an underpainting for you. You can easily remove parts with a cloth or the flat of the brush to create lighter places…a bit like sketching with paint.

Best regards Anne.

(Geoff) #3

Hi Anne,

I’ve never tried an alkyd medium, but I’ll go ahead and get one and give it a whirl. Thanks.

My “go to” for an underpainting/sketch has lately been Transparent Red Oxide, so maybe I’ll try mixing that with a wee bit of alkyd medium. Yes, basically I want to sketch with paint – and then paint over the sketch with confidence that the sketch won’t bleed into the upper layer.

Anyway, I’ll order some alkyd medium and see how it goes. Thanks again!

  • Geoff

(Gary Bruton) #4

You can also use acrylic to underpaint. Lots of research shows that oil on acrylic is fine long-term. But acrylic over oil is not safe long-term.

(Geoff) #5

Thanks. Yes, I’ve tried acrylic for underpainting; it works fine. Even acrylic does need a few minutes to dry, it seems; sometimes I start painting over it, and things are still a bit tacky. I guess thinning it with water a bit would help.

(Linda Olsen) #6

I’ve thought about trying guache as an underpainting medium. It dries quickly. I know it reactivates with with water, but I don’t know if the moisture from oil paint is enough to do so. Another thought is oil pastel - I tried it once and didn’t have any problem with it.

(Nancy Tankersley) #7

Have you tried Bio-based Thinner which is made with soy rather than petroleum? It’s available though www.arttreehouse.com . It acts just like OMS without the toxins ( as far as I can tell). I too really missed the ability to draw and block in with a thin quick drying layer and just couldn’t adjust to an oils only method. Until someone tells me the downside, this seems to be the answer!!

(Joseph Mahon) #8

Hi Linda, I don’t think gouache as an underpainting is a good idea. Water and oil do not mix and gouache is water based. The foundation layer of gouache is not set for an oil over painting would not be good at all. There is little or no alternative to solvents in the early stage of oil painting. Once the initial stage is over then there is no need for medium at all, if desired. Gamblin do a solvent free gel.

(Linda Olsen) #9

Joseph, I think you may be right. After thinking about it I can conceive of archival problems with a gouache underpainting, so best just to can the idea. I think the best suggestion was to use a alkyd medium or buy some alkyd paints to use just for underpainting.


(Veronica Brown) #10

My “go to” is also Trans Red Oxide and I’ve used Gamsol Galkyd medium and like it alright. It’s not as thin as if I’d missed with OMS but, it did the trick and I was able to get a drawing that didn’t “muddy” my top layer. :slight_smile:

(Geoff) #11

Veronica: I just got some walnut alkyd medium from M. Graham; I’ll try that with transparent red oxide.

Nancy: that soy-based solution looks intriguing! I’m going to order a bottle today. I’ve read good things about that website elsewhere, so I appreciate the tip!

(Sharon Egan) #12

Hi Geoffrey -

Try Gamsol by Gamblin. It’s the safest OMS!

Not sure if this link works, but if not, copy and paste:


(Geoff) #13

Thanks, Sharon. If I do break down and use an OMS, Gamsol would likely be my choice. I just worry about long-term exposure to it in my studio, which isn’t the best-ventilated studio on earth. Some say that odorless spirits are more worrisome precisely because you don’t smell them, and thus don’t sense when they’re invading your head. I dunno.

I received my bottle of Bio-Thinner from the Art Treehouse and gave it a try. It thinned the paint nicely, like OMS. I used it to paint a ground over a panel, and I also used it to wash brushes. It made for a nice thin wash, and it was effective as a brush-cleaner too. I don’t love the orange-citrus smell, though; it reminds me of Turpenoid Natural, which always has struck me as somewhat unnatural. I worry that inhaling the stuff may be no better than inhaling an OMS like Gamsol.

For cleaning brushes, walnut oil has long worked fine for me, and I’m inclined to stick with that. But walnut oil won’t do for an initial wash, so I’m going to continue to experiment with this Bio-Thinner product.

Incidentally, soy-based solvents apparently live a bit of soy residue behind, unlike OMS, which evaporate entirely I suppose the worry is that the soy solvent won’t create as strong a bond in the long run? I have no idea whether this is anything to be concerned about.

(Lavina Blossom) #14

Hi and welcome. I am hyper-sensitive and cannot use any traditional solvents or mediums. I use Eco oil medium (made in Italy and available from Blick) to thin paint for the sketch and to thin very thick paint while painting. I use Turpinoid Natural to clean brushes. Both are nontoxic. The Turp Narural has a slight odor but not a bad one. I should add that the last time I ordered Eco oil medium from Black that it was backordered and took a couple months to arrive. I am hoping this was unusual and I won’t have the same problem in the future, but who can know.

(kathy Rivera) #15

I use Gamblins Neomeglib medium to thin the paintnd it drys fast, no odor.

(Geoff) #16

Thanks. I might try the Neo meglib medium. Lately, though, I’ve simply been thinning the first layer by using a water-miscible oil diluted in water, then switching to “regular” oils, then thinning later layers with walnut oil. Seems to be working well so far.