PDA

View Full Version : Why add solvents to a slow drying medium recipe?


piston_pounder
03-18-2019, 10:27 AM
I often have to leave my paintings for a day or more before I can continue on it. I like the wet on wet method for simplicity during my days of learning and not having to think about different pigments drying faster and factoring that into a fat over lean ideology.

I have been adding just straight purified linseed oil which I find dries slower than plain linseed oil and adding about enough to make the paint a ketchup consistency. This gives a good 36 hours of wet paint before the faster drying pigments start to get tacky.

I was reading a bit more about oils that make it even slower and I've come to the conclusion that I will use walnut oil as well and maybe clove oil but the clove seems to be a bit extreme. I'm looking for about 72 hours of wetness.

So my question. All the slow drying recipes I come across recommend adding OMS or even some sort of turps along with oil medium... doesn't a solvent speed up drying time? Why would you add a solvent to a medium that you want to take longer to dry?

midwest
03-18-2019, 11:35 AM
Dont use turp or oms, it will definitely speed up drying time.

Pinguino
03-18-2019, 12:34 PM
1. An ordinary solvent (such as OMS) does not significantly "speed up" drying time. What happens is that the solvent evaporates quickly, leaving the (oily) residual. The with-solvent paint has different handling properties than the no-solvent residual. This creates the false impression that the residual is partially dry. I have seen it said that the solvent makes it easier for oxygen to penetrate the paint; but I doubt that.

2. However, if the mixture is very lean (significant amount of solvent), it can be spread very thinly, compared to paint without solvent. In this case, the no-solvent residual can absorb oxygen more quickly, thanks to the thinness of the layer. This will cause the residual to dry more quickly than otherwise.

3. Clove oil is not a painting medium. It naturally contains a chemical that has anti-drying properties. Some artists store their palettes in a sealed container that has clove oil vapors. The idea is that some of the vapors will interact with the paint surfaces, preventing them from absorbing oxygen as fast as they otherwise would have done. Although this may or may not work as well for a painting (not just a palette), I do not know if anyone does that.

4. Refrigeration is a good way to prevent paint from drying too fast. If your canvas or board is small enough to fit in the fridge, try it. Works very well for palettes. Freezer is even better, for water-less paints. Or, if you live in a cold climate, a cold outside location (or garage) might work.

5. If you really want to go high-tech and have the money, you can put the painting in an oxygen-free environment between sessions. Not advised.

6. In any case, wet-on-wet is difficult for newbies, AFAIK.

sidbledsoe
03-18-2019, 02:25 PM
Yes, adding more solvent to oil paint does in fact result in significantly faster drying of the paint film. It does not speed polymerization, what it does is that it rapidly disperses the oil, thins it out, makes the paint leaner, and thus the paint will dry faster than a thicker, more viscous, non dispersed, more oily paint film.
Not only that, but there is always a certain amount of absorption, not only in raw, dry canvases, but in previous paint films themselves, especially if they are matte. So the thinned out paint will also absorb faster and to a greater extent, making the paint film drier from increased binder loss. Sometimes people claim that their solvent diluted paint dries in a matter of minutes.
It isn't polymerizing, it is simply absorbing rapidly.
So my question. All the slow drying recipes I come across recommend adding OMS or even some sort of turps along with oil medium... doesn't a solvent speed up drying time? Why would you add a solvent to a medium that you want to take longer to dry?
Solvent is added to slow drying mediums to thin the medium. The slow drying quality of those kinds of mediums is not overcome or eliminated by the solvent. They still have the clove oil, or slow drying oil, or whatever that slows the drying a lot more than the solvent would be able speed up.

AnnieA
03-18-2019, 02:41 PM
I am one of those who uses clove oil-soaked cotton balls in my Masterson box to retard the drying of paints on my palette when stored. It works well for me and I haven't seen (thus far) any problems with this method. But I've read that if mixed with paint to be used in painting, it can degrade the paint film. I've seen clove oil melt a plastic bottle that I had some stored in, so I would never use it in a painting.

I've never tried it, so I have no idea if this would work, but perhaps it might be possible to store a whole painting in a contained environment such as a Masterson box (one would probably have to clip off the small cylindrical pieces attached to the top to use an M-box for this, unless painting on a flat panel). Theoretically, istoring a painting in an air tight container would keep the paint fresher, and if it were possible to then put the box in the fridge or freezer, that would be even better. Perhaps a small drop of clove oil on a cotton ball in the box would be better still. Please note - this is only speculation on my part, but it seems logical that this would work, since the same approach will keep oil paint open longer on a palette.

WFMartin
03-18-2019, 03:50 PM
Generally, oil painting mediums are added to oil paint for one, primary purpose, and that is to cause the paint to "handle better" for the effect you are trying to create. In some cases that may call for a stiff paint, and in some cases a more fluid paint would perform better.

When added in different ratios to an oil paint, a medium should be capable of causing the paint to behave in such a manner as to make your life easier, in terms of applying the paint to the canvas. One should never be required to "do battle" with, or to need to"outsmart" your chosen paint medium, in order for it to perform well with your oil paint, when creating a painting. Often, one will ask whether there is any noticeable difference in final appearance between a painting done with a medium with which one had to do battle, and one in a medium that made the paint application easier. In such a case, I always search for paint strokes that appear as though it may have been a "struggle" to apply. And, yes, such an appearance is often evident.

When a painting medium has been engineered appropriately to make the paint application more appropriate, it is a great aid to the painting process, and, as a result, to the final painted work.

A sound painting medium is often composed of both a drying oil, such as Linseed, or Walnut, and a solvent, such as Turpentine, Odorless Mineral Spirits, or Oil of Spike Lavender. By choosing from any number of these ingredients, and by varying the ratios among them, you can easily, and quickly, engineer a medium that will fit your needs for nearly any sort of application, and for any effect you may wish to create.

And, by doing so, this can allow you to be able to choose from a great array of oil paint brands, and rest assured that your medium will have the capability of causing the paint to handle the way you want it to handle, regardless of the paint brand you have chosen.

Among the characteristics of oil painting mediums, drying time may be one of them, but drying time is by no means the most important of the characteristics. I would gladly trade the characteristics of "fast-drying" for a medium that causes my paint to flow precisely as I want it to flow. That makes my life easier, I have found.:)

DAK723
03-18-2019, 03:58 PM
One reason it is recommended to add a solvent to a medium is that you can use more medium. So it may not be related to drying time. If using only solvent or only oil, the recommendation is to use very little as a medium (some recommendations say no more than 10%) Using too much solvent as your medium runs the risk of creating an underbound paint. Using too much of a 100% oil medium runs the risk of wrinkling or creating a too glossy surface. So the usual recommendation for a medium is to include both an oil and solvent allowing painters to use as much as 25% (or more) medium to paint. Of course, in actual usage, you may not have any problems using a 100% oil medium, so recommendations can usually be taken with a grain of salt.

Don