Hello Everyone,
I find that when I need to apply a couch to paint into to merge my layers and match my value, sometimes my previous color layer starts wiping off, destroying hours and hours of previous work. This never used to happen when I was more reckless in my early years. But now I paint solvent free and use as little medium as possible. For context I paint on museum quality gesso board (acrylic ground). I use lead white and typically do my underpaintings with a mars color and white or old Holland raw umber. Sometimes I seal my drawing with acrylic matte medium, sometimes just a light layer of raw umber and lead white. What I can’t seem to figure out is if my under layers are underbound or if the couche I’m applying is the cause of delamination. It was my belief that a couch would not only make each new layer fatter but INCREASE adhesion and not the opposite. I typically use oleogel or walnut gel as a medium. Does anyone know what could be causing this issue?
I had this problem when using a well known alkyd medium. Well I didn’t use a couch, but the the second layer would partially dissolve the first. The more medium I used, the worse it got. I deduced the effect was caused by the alkyd medium quick dry setting up, but not being truely dry the next day. The solvents already within the gell medium then acted on the first layer when painting the second. Your cause however may not be the same,
Marc.
Thank you for the quick response. This particular painting is on golden acrylic ground. The underpainting was done with raw umber and lead white. the first color layer was then done with no medium and a limited pallete of mainly mars colors. This was initially for a show in June but because of Covid-19 it was pushed to December so I took a hiatus on the painting. So that color layer had quite a few months to dry. I then applied a couch of oleogel from Rublev and applied a second layer, this time with a more open pallete of opaques and transparents. After about 8 days I repeated this process and while applying another couch the paint began wiping off, only in very specific spots. Particularly in the lightest areas where the most lead white is. (The underpainting is done similar to that of Rembrandt). When I noticed it delaminatiing I abandoned that sitting and waited another week and a half. But alas, last night it happened again in the upper area of the form. This time I just scrubbed that whole layer off and repainted it. This also happened on another painting except in the black glazed areas. However that painting was done with a mars black/lead white grissaile and on gray acrylic ground and later layered with a leaded glass medium that does contain solvent. I’m completely baffled.
John.
Oh and to answer your other question. I’d say that the main thing that has changed in my process is that when I was younger I was much more liberal with my use of medium. I’d use medium from the very beginning to the end. Dipping in medium and into paint carelessly. Now I barely use it. In fact, I only really need medium to bring back the surface so I can match my values as I try and finish my work. That and to make my later layers a little fatter. Also, when I “seal” my drawing, its less about sealing it as it is just to tone my substrate so I’m not starting on a white surface. Could it be that gel mediums arent quite mixing with the paint when I apply a couch and therefore kind of getting sealed wet, between a dry layer and a wet layer?
I am not sure that I can completely and satisfactorily answer your dilemma with just the info at hand. I wonder how long you are waiting before applying subsequent layers? Is the isolation acrylic dispersion layer perhaps creating a slick surface diminishing adhesion? (I see no reason to lock in an underdrawing for oil painting when applied over a “relatively” non-absorbent surface, as compared to a chalk-glue ground or true gesso). Is your couch truly solvent free? What else has changed from your previous practice? If you are working solvent free it would seem that your underlayers would be fully bound, perhaps they are overbound? This has always been a worry of mine when people speak about solvent free painting. It is certainly a sound idea, but it needs to be approached as thoughtfully as solvent thinned oil painting.
As to a couch of medium, the concept is fine as long as you are going to cover all of it with pigmented layers. Please see our Resources “Varnishes” section for particulars about oiling out.
I have honestly never had this happen when oil painting, except as a student when painting on an overly fat surface or when I stupidly tried to apply a coating in an overly aromatic solvent over recently oil layers for some foolish expedient.
Let us know the answers to the above and hopefully I/we can be of more help working through this difficulty.
Rubelv Colours Oleogel consists almost entirely of linseed oil without solvents and driers, so it is hard to imagine that it could be the cause of this issue. However, it would be good to eliminate it as a cause by substituting it with linseeed oil for your couches.
Many artists believe that the application of “couches” or a layer of pure medium or oil onto dried paint increases the strength of the paint film, but I am not aware of any evidence or studies that bear this out.
Unless there is a need to match colors between dried paint passaages and new paint, there is little reason to oil out or apply a couch before each painting session.
In terms of what may be causing paint to lift off when applying the couch you need to look closely at the structure of the underlying paint film. You did not state it but did you apply the underlying paint with a solvent? How much Oleogel was added to the paint? When paint is lifting off, does it expose the ground?
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