MITRA Forum Question Details

​First and foremost, I think, is realizing that oil paints in general need light to form a good film. There are exceptions of colors that will still dry in the dark - cobalt blue and raw umber are two that we have tested - but many colors simply will not dry if kept in the dark, and can take extremely long in semi-shadow versus exposure to full indoor light. just to give one example, Cadmium Red Medium in 'regular' studio lighting, 6 mil film, dried in 7 days. When kept in the dark, it took 135! So more than 4 months. In open diffused shadow, it took 16. You can find similar data in Gettens and Stout's Encyclopedia of Artists' Materials:

https://play.google.com/books/reader?id=X09r_D3mpFgC&printsec=frontcover&pg=GBS.PA40.w.1.0.37

The graph is small.....but the top dark line is linseed in light, the bottom linseed in the dark. For the dark cured linseed, the tack free stage of drying was not reached for nearly 70 days. Keep in mind this is also linseed oil alone in a very thin film - and of course pigments and other additives can impact it further, both in terms of speeding it up or retarding it even further. The main point is that having little to no light can severely retard and slow up the drying process, and I would not recommend ever drying paintings in dark storage.

Second, you do not state how much clove oil you added to your medium but we are not fans of adding clove oil into paints. It is an extremely powerful antioxidant and, while you have seemingly had luck in the past, future results (and clearly present ones as well) can differ. If you need to have more open time in an alla prima process, we would recommend trying to use poppy or safflower oil as safer.

As for what to do now, our experience has been that even the most intransient paint films have eventually dried . The worst we have seen in testing was nearly 6 months, but dry it did. So, have patience, keep it in the light, and if you have a sunny day or two coming up, and none of the colors you used are vulnerable to fading, then having it exposed to direct sunlight would help as well.  We would not recommend trying to spray on or add to the top surface any driers. Trying to force things at this point only risks more complications and potential problems down the line. 

Hopefully others will have additional thoughts, but that is our advice.

​I would echo Sarah's caution against use of essential oil of clove in mediums. The main antioxidant component (eugenol) is not standardised from brand to brand, and last time I investigated, it seemed there was a significant difference between the same product from several sources so I think it's probably very difficult to measure reliably. I also agree that later adding a product which accellerates drying will make the paint film very complicated and may yield unpredictable, undesirable results.

(Regarding the Krylon drying spray, when I inquired, the manufacturer would not explain exactly by what mechanism the product acts on the paint, but I did discover from product literature that it includes an anti-skinning agent used also in industrial paints which prevents a skin from isolating the interior of the film from contact with the air, and reduces the chance of wrinkling when top-driers are used.)

It might also be worth noting that ambient temperature can affect the drying rate of oils. This time of year, depending on where your studio is located, low temps may just be slowing things down. If you are patient, the clove oil will evaporate and the paint will dry, though the resulting film may have been affected by the presence of clove oil, dependng on concentration.

​Darn. I see that my fellow moderators beat me to this and did so with some great info. Oh well, here is what I wrote:

Sorry to hear of your problems.

If you search this topic on MITRA you will see that I have real misgivings about the use of clove oil in oil paints. I also stated my reservations about using its vapors to keep oil from setting. We know that solvent vapors can penetrate and change even dried oil paint films and it seemed more than reasonable that it could do the same to fresh oil paint. I have discussed the use of clove oil with a number of painters who formerly used a medium similar to yours and they said that even though the paint generally set after 28 days or so, the final film was always rather soft. Anyway, off of my soapbox.

It seems likely that the natural drying curve of the oil was so disrupted that it is not able to oxidize properly. First, please do not use the spray siccative. There are so many problems with that concept.

1 It seems like you have three real options. Why not let the painting sit for a while longer to see if the drying was only slowed and not completely disrupted? There can be no harm in this and you can always proceed to numbers 2 or 3 if necessary. You should not paint on top of the problematic paint, or frankly the painting at all, unless it does oxidize. Doing so would set you up for wrinkling, cracking, and possible delamination down the road. I do fear, however, that the lengthy period of time that you report suggests that option 1 is sort of a long shot.

2 It may be necessary to remove all offending paint from the surface, wipe the surface with OMS and apply new paint.

3 If you find that too much of the painting is effected, you may need to start over.

Why not work on another composition until you know whether you need to follow plan 1, 2, or 3.

​While unusual, because so few go in the direction of slower, you could probably get a painting to stay open a long time if you worked with a slower drying oil, like Poppy, then opt for all slow drying pigments - so eschewing Burnt Umber for, say, a combination of Cadmium Red and carbon black, and so forth. Like I said, it runs counter to what everyone chooses, and forces you off a lot of the earth colors, but it will stay open longer. Just know that many of these slow drying colors form soft or weak films. Its all a tug-awar in a way.

Lastly, keep it in as cool and dark a location as possible -between sessions  but NOT in your freezer - and leave out the clove oil. Taken together I think doing all these things  might keep a painting open for days. Worth a try perhaps.

Or one could place the painting in a sealed container filled with nitrogen gas....okay, a little extreme, but.....

:)

Sarah

The painter I referenced in my post wanted to work completely wet-into-wet and yet have ample time to work through the painting contemplatively. I have known a few painters who felt and worked this way, but it is in no way the norm.

Great to hear - thanks for closing the loop. Patience, light, and warmth will usiually do the trick!