Published: 16 September 2017
Today we're offering a few easy ways to tell oil apart from acrylic. Next time you're at the RA or Tate, or the PV of this Autumn's slew of fairs and openings, you can put these simple tips to use when taking in a painting.
Oil paints have been around for much longer than acrylic, and the majority of paintings in this world produced before the 1950's were executed in this medium. Before the technology was there to improve and innovate paint and its properties, artists trained to mix their own paints through a combination of powdered pigments and a variety of oil bases. Oil dries slower than acrylic, which allows artists to achieve smooth blends between colours and affords painters a longer window of opportunity to paint 'wet into wet' (resulting in a gestural, free apperance of strokes) on the surface.
Thickly painted oils can take a number of years to entirely dry. When they finally do ossify, the topography of oil paintings are hard to touch. The peaks of a dried oil painting look sharp and crisp, as though defying gravity. Mass and 'impasto' (thick, built up passages of paint) are best acheived through mixing supplementary substances into oil. When the impasto technique is applied, it's usually through fortified oil paint.
If an artist wants to create an oil wash, the addition of spirits and other thinning agents occurs. Often artists will sketch in a very light, thinned oil wash to lay out the framework of their painting's first layer.
Acrylic paint was made commercially available in the 1950's. Artists working in this medium enjoy a shorter drying time (to work more quickly from layer to layer) and a wider range of 'unnatural' colours that oil paint can't yield. This includes neon hues and metallics like gold and silver. If a painting is dated before the 50's, you can rule out the possibillity that it was executed in acrylic. Most artists were excited to use acrylics because the price point was lower than oil, and they could create larger more ambitious works at lower cost.
Most acrylic is plastic and water based, so diluting the paint for a wash is easily done with water. Thickening arcylic to paint impasto is achieved through the addition of a variety of mediums, but does not acheive the same effect as oil. Although acrylic dries to the touch faster than oil, it is primarily plastic and water, whose molecules never fully settle and 'sit still'. This causes the peaks of acrylic paint to appear rounder and softer than those of oil.
SUMMARY: TELL OIL AND ACRYLIC APART
To recap, the top tips for telling oil and acrylic apart are:
OIL- sharper peaks, natural colours, 'wet into wet' blending of palette, impasto passages
ACRYLIC- softer peaks, unnatural (neon, metallic) colours, flatter appearance