Old oil painting with linseed and stand oil underpainting is starting to drip

Hello,

I sold a painting about 9 years ago to someone who got in touch recently to inform me that the painting had deteriorated over time, with drips of brown goo running down the surface.

For about 11 years, I’ve been working in oil paint and oil pastel on canvas.  When I start a painting, I generally prepare the surface with a combination of linseed oil and stand oil, sometimes applying multiple layers and allowing them to dry between coats.  This is to provide a kind of buffer between the paint and the canvas so that the paint can be more easily removed, keeping it workable.  In addition, I often squirt this linseed/stand oil solution onto the painting while I’m working to keep the paint wet, and to add a drippy quality.  I’ve seen – and still have in my possession – many of my paintings from the era of this painting and earlier, but this is the first time I’ve seen this fairly catastrophic degradation.

I’m not sure exactly what happened here, but I’m guessing that for this particular work, I applied the linseed/stand oil undercoating in big globs instead of in a smooth coat, and puddles of it congealed such that the outer surface solidified but the interior remained liquid.  Then over time, the outer layer cracked/dissolved, and inner liquid oozed out.

The challenge now is to remove the drips while minimally affecting the underlying painting.  The patron says “the drips have been going for some time”, and describes the substance as “tacky/sticky to the touch” but “not wet exactly”.  My first thought was to use a dry paper towel/napkin/rag to remove the bulk of it, then go over it again with a paper towel/napkin/rag damp with soapy water.  If there is still a residue, I thought carefully wiping it with a rag soaked in mineral spirits (or a comparable substance that a non-painter might have lying around, though I don’t know what that would be exactly – ethyl alcohol?) could clean the final bits.

Can anyone advise on how to clean this up?  Also, how can I prevent this happening in the future?  I have not been in the habit of varnishing my work, but I’ve been thinking of starting to do so.  Might that prevent such calamities?  Note that my technique is experimental and largely of my own invention so I’m still not sure what long-term hazards it poses, and am keen to ensure my work preserves over time.

Thanks very much,

Jeremy.