![]() ![]() Paint is a complex mixture of chemical ingredients. Every minute bit of paint is not all made up of the same molecule like (for example) pure water or pure sugar. High viscosity paint will smooth out more slowly than low viscosity paint, it will flow more slowly, and drip more slowly, and it will retain the details of a brush impression for longer.īut there's more! Paint is not made up of one ingredient. It also makes it harder for the inside of the splotch of paint to rearrange itself. The takeaway so far? Higher viscosity makes a splotch of paint harder to move around. This is actually a bit of an oversimplification - there are other properties related to viscosity that also need to present to keep paint from becoming smooth before it dries or hardens. Gravity and spreading can't pull the paint completely flat in the time it takes to dry or harden the paint. If you paint using a thick viscous impasto medium, the viscosity helps keep the brush texture in the paint, because a viscous fluid will take longer to smooth itself out than a non-viscous fluid. The individual small areas within a splotch of the thicker more viscous paint are also better at staying put. The "thicker" more viscous paint resists gravity better, and doesn't slide down the canvas - it stays put. Both of these actions affect the viscosity of the paint, along with a number of other properties. If you work with oil or acrylic paint you have probably tried to tweak the properties of the paint by "thinning it out" or by "thickening it up". Gravity moves the turpentine out of the glass more quickly and effectively because it has a lower viscosity. Which glass empties more quickly? Unless you're reading this from some alternate universe with different properties, the turpentine empties more quickly. The liquids start pouring out onto the table. ![]() A cat comes into your studio and bats both glasses onto their sides at the same time. The other is half full of stand linseed oil, a higher viscosity fluid. One is half full of turpentine, a low viscosity fluid. ![]() To visualize viscosity think about two identical glasses on a table. The "push" moving the fluid doesn't necessarily involve actually pushing (or squeezing a tube) with your hands and fingers. A more viscous fluid needs more of a push than a less viscous fluid. The "amount" of viscosity a fluid has tells you how hard you would have to push on it to keep it moving. So what is viscosity? In layman's terms viscosity is the thickness of a fluid or paste. This allowed the pigment particles to fall to the bottom. Mixing up a more fluid paint for glazing reduced the paint's viscosity. Have you ever mixed up a batch of very thin paint for a wash, and then left it overnight in a sealed container? The next day the paint may still be fluid and usable, but often the pigment will have settled to the bottom or the liquids will have separated. Sometimes we thicken the paint using wax or impasto medium so that the texture of our brushstrokes is retained. When we mix up oil paint, we sometimes make it thinner using turpentine or solvent so the paint flows more easily. ![]()
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