MITRA Forum Question Details

​Many thanks for your replies, Brian -- I appreciate your patience with my response as I got quite busy there for awhile and didn't have time to follow up until now.

The "situation" was indeed difficult to photograph. Essentially, once the turp evaporated that I had used to clean the surface, it looked like I had applied an extrememly thin, dull white glaze with my rag. 

It sounds as though eventual varnishing will mitigate this milky appearance wherever I am not overpainting. I just wanted to check that overpainting wouldn't be an issue here, since I do need to apply the final highlights and shadow layers to this passage of midtone colors. 

Also, another issue I have is that a very small area that essentially ended up being rather accidentally sanded as I tried to remove a small, stray glob of paint that had fallen when I was working on the top portion of the canvas, but I didn't realize it until it dried. I might have left it but I knew it was violating fat over lean. I assume I can just paint over this area without issue, following the fat over lean rules regarding the surrounding layers? I'd say it's maybe half to 2/3 the size of a US dime, so in the grand scheme of this large canvas, it's an extremely small spot. I know some artists sand layers as a routine part of their practice -- the airborne pigments are likely the main concern there, right?​

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Thanks, Brian. Now I have another strange issue with the same painting that I think must have also been caused by wiping it with artist's rectified turpentine when I was cleaning it, then wiping again with OMS to remove any turps residue as I previously described.

This happened as I painted a passage last week 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 layers on this underpainting, I'm using a 60/40 fatter ratio, and in both layers, the paint is adulterated 20% with my medium mixuture. The substrate is high quality, stretched linen canvas, and if it makes a difference, my studio relative humidity percentage is really low right now (like in the mid to high 20s).

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 managable 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 inadvertantly 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.

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 not underbound. Would oiling oil 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 subtle white filmy rings look 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?

I'm attaching a few photos of this oil leaching situation. It will look 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. I haven't been back to the studio since this happened, so I hope I don't find out that it leached more after I left, as it will now be dry. 

Many thanks! (It looks like this post was initially wiped out by the photos I just attached, so thank you for your patience if it gets duplicated.)