I thought it might be useful to define some of the different media that you hear artists working with in their original artwork. I have worked with most of them at one time or another and so I have familiarity with them.
The medium I’m working in right now is acrylic. Acrylic is a 20th century innovation, made of polymer medium, in which particles of pigment are suspended. This is just a fancy way of saying that it’s liquid plastic with color in mixed in. When you have a painting that is painted with acrylic, you have a very durable surface.
Acrylic paint adheres well to just about any surface that it is painted on. You may also have heard about mediums, like gel medium and gloss medium. They are colorless formulations of the liquid plastic that have different characteristics and viscosities. There is gel medium which is thick like cake frosting and it can be either gloss which is shiny, semi gloss or matte which is not shiny at all. Some of the mediums are thinner, more liquidy and others are completely solid, kind of a Crisco thickness. But they will dry clear and give different kinds textures to the surface.
Next is oil paint. Oil paint was used for centuries and most of the great classic paintings you see in museums were made with it. It has color pigments suspended in a linseed, natural oil base.
With the oil paint one needs to use centers such as turpintine to clean it. Generally takes quite a long time to dry as opposed to acrylic which dries minutes. There is a special luster that comes from oil paint which is hard to reproduce.
Then we come to pastels which had been my medium of choice for a long time. In the art world when you refer to pastels, it generally means the dry, chalky type. However, they are not chalks. They are solid sticks of color. There is only a small amount of binder used to make the color solid and when you apply it to the painting surface, you get exactly the color you hold in your hand.
Once the painting is done, the loose, dusty particles can be made more stable by spraying on fixative but when pastel paintings are handled or moved around a lot, frequently dust will loosen from the painting. That makes it very hard to ship to juried shows and that problem is what made me move on to acrylic. You may be more familiar with oil pastels that some artists use but are frequently used by children. These are similar to oil paint in their taking a very long time to dry.
Our next big category is watercolor. What are color paint comes in either tube or cake form and you use water to dilute it and make the paint liquid. When applied to paper it is transparent and so has a beautiful light contained within it.
There is also gouache which is a form of watercolor where the paint is opaque and you cannot see through it. This is frequently the medium of choice for designers. This paint has a matte, not shiny finish.
I hope this clarifies some of the differences the time to paint that artists use and that the next time you go to an art gallery you will find it easier to interpret the labels under the paintings.