As any oil painter will tell you, no medium is as rich and versatile as oil. But what makes oils so desirable also makes them challenging to work with. Because it takes so long to dry, one must work wet-into-wet. For the beginner or novice, this can present a considerable technical challenge. Acrylics are the obvious alternative, but they have drawbacks, as well: they have a plastic-like feel that many artists do not like; they dry too fast (nearly instantly if you’re painting outdoors) and worst of all, they dry as much as 15 percent darker!
Fortunately there is an alternative which few artists have tried. Imagine a medium that offered all the advantages of oil — versatility and buttery feel — but in a quick drying form, and with none of the disadvantages of acrylics.
Alkyds dry much faster than oils, but slower than acrylics. The paint remains workable (wet) for many hours, depending on how thickly it is applied, the temperature of the environment, and whether or not any additional alkyd-based painting medium is added as you work. In my experience, alkyds begin to dry (get tacky) within an hour, making them ideal for plein air painting. You can blend wet-into-wet or, later in the session, rework areas (wet over semi-dry). Both impasto and glazing can be achieved in considerably less time than oils.
On a scale of 1 to 10 — where 1 is pure plastic and 10 is oil paint — I would say that acrylics are about a 3 and alkyds are an 8. Some painters describe some of the alkyd colors as sticky.
Fully compatible with oils. Alkyds should not be confused with water-based oils. Alkyds can be mixed with regular oils and are reduced with the same solvents. TIP: In order to speed up the drying time of regular oils, I often substitute a few of my most frequently used oil colors for alkyd colors, such as white and ultramarine blue. Because these colors are used in so many mixtures, it speeds up the overall drying time of all my colors.
Regular oil paint can be layered over alkyds, but it is not recommended that alkyds be layered over oil, as the less flexible alkyd film may crack. Chemically, alkyds are made from pigment and oil-modified alkyd resin, which acts as a binder and causes the paint to dry more rapidly.