MITRA Forums

I am reposting my latest question since I now have a new issue, previously discussed under the thread about white-looking filmy rings of presumed impurities that were brought up by cleaning an in-progress painting with artist's rectified turpentine then wiping again with OMS to remove any turps residue. I have another strange issue with the same painting that I think must have also been caused by cleaning it with turps.

This happened as I painted a passage two weeks ago in the area I had previously wiped-down (long evaporated), which to recap was a mechanically-thin underpainting on acrylic dispersion primer. I'm using professional grade oils suspended in walnut oil, with a walnut oil/alkyd medium. The underpainting was done several years ago using a different brand of solvent-based alkyd medium, mixed 50/50 with OMS. In my second, current layer on this underpainting, I'm using a 60/40 fatter ratio, and in both layers, the paint is adulterated 20% with my medium mixtures. The substrate is high quality, stretched linen canvas, and if it makes a difference, my studio relative humidity percentage was really low when I last painted (in the mid to high 20s) with a temperature of 72F.

I've been working on this piece for several months with no issues until I wiped the lower part of the painting with the turpentine as I mentioned previously. It's a huge canvas, so I have to paint one manageable area at a time. What happened recently is the first time I've ever seen anything like this happen in the several decades that I've been painting in oil paints. I noticed after I had completed this particular passage that the walnut oil was leaching out in a thin ring around the edges, as one might see had it been placed on paper or a paper palette. It happened both onto the adjoining underpainting and the adjoining long-dry area with a second layer at 60/40 (the green grass in the attached photo). I knew it would be bad to leave a "bare" unpigmented oil edge like that, so the only thing I could think of to do was to wipe that oily edge off with my lint-free rag with OMS, then retouch the edges of the areas so they weren't inadvertently too lean. I kept having to work back and forth until it wasn't leaching out anymore. There were a couple of places where I was never able to reapply paint on the edge without it continuing to leach, but I was wiping very carefully, so I don't expect it to be too lean at the edge.

Unfortunately, when I returned to the studio this week, I discovered that the leaching may have continued in a few spots. It's hard to tell, since I do see a darker outline, but it doesn't look as shiny as the main passage. I know if I overpaint unpigmented oil that it could cause adhesion issues, but it I leave the areas that they can discolor over time, so I wondered about carefully sanding these edges? It's the only thing I can think of, so I welcome your expertise.

When I was painting this passage, I recall feeling that when the brushes went down, the surface had a different "drag" to it, an almost "squeaky" feeling, so I suspect that somehow, by using the turps, I disrupted the oil layer of the underpainting, though it is definitely not underbound. Would oiling out the next area before painting each new passage take care of this? I don't usually oil out as I work, and I know you have to paint over it lest it turn brown eventually if left bare. If this is the solution, I'm also wondering if this would be enough oil to affect my fat-over-lean ratio. Since it is difficult to always predict what organic shapes my textures will take in each segment of working on this huge canvas, I'm a little concerned about oiling out, unless it isn't as difficult to manage properly as I am thinking.

I don't yet know if the grass areas with the previously discussed subtle white filmy rings of impurities that also resulted from this turps application will behave in this same way. I really hope not! And just to dot the I and cross the T, did you think that I'd be able to overpaint those affected areas with highlights and shadows without those presumed impurities coming up to haunt me later?

So my three questions are: 1) how to continue painting the areas near the passage that leached oil to keep the leaching from happening again, 2) how to handle the now-dry areas of presumed oil outlines that look like they continued to leach from this passage after I left the studio, and 3) if I can overpaint the areas where white filmy impurities were brought up by turps.

I'm attaching a few photos of this oil leaching situation that were taken prior to my efforts to correct the situation. It looks like a darker gray pencil line of sorts. I haven't been able to find anything about this phenomenon, so I can't tell you how much I appreciate your help. This is a very large work for which I have received grants and have a deadline, so for both financial and time reasons, starting over isn't an option.

Many thanks!