Learn to paint in Acrylic paints - Step by Step
Only if you want to have a really smooth surface to paint on.
For myself, I like to have some texture to the canvas - especially for landscapes. I don't do any further gesso.
The only time I might is if I were doing a portrait or working in a style with a lot of detail...
Ah--good to know that. I guess I haven't painted on enough canvases to know exactly what I "like" texture-wise--but to know that I probably "need" more gesso for something with a lot of detail helps. Thank you, Karen!
I have posted previously a blog on preparing substrates, but in a nutshell:
Unless you are buying professional canvas (with its premium price), you have no way to know if the manufacturer prep is decent quality. With oils this is not as big an issue. Latex and/or acrylic paints use water as the diluent, and the water penetrates the canvas when the paint is applied. As the water evaporates from the paint surface, any acids, lignin, or other impurities in the canvas can be drawn into the paint film and produce discolouration of the paint film. The physical nature of acrylics leaves small pores in the paint film, so even high humidity after the paint is dry can add to the problem.
Gesso is not a sealer. It's purpose is two-fold - to provide a uniform "white" surface, and to provide "tooth" so the acrylic paint will adhere to the surface and not tend to lift or peel off.
A sealer suggested by Golden is gloss medium, applied in two coats. This gives a denser and more water-resistant film which minimizes the transfer of water to the substrate. Additional top coating with gesso then provides the tooth for a working surface.
I assume all canvas to be improperly sealed, by default. Each is given two coats of sealer over the original gesso, and after drying completely is given at least one coat (usually two) of gesso. I use the same basic protocol for paper, canvas panel, and wood surfaces.
Do make sure your canvas is acrylic primed, oil primed canvas should not be used for acrylics.
If you go to my member page, you can see the original blog posts, which are somewhat more detailed. I have had to destroy several early acrylic paintings due to substrate discolouration, so I tend to err on the side of caution. Please feel free to ask if you wish more input!
Wow, Charles, thanks very much for the in-depth information! I really appreciate it. I will pick up some sealer for my "real" attempts, i.e. anything that is not just practice. I will take a look at your member page, too. Thanks again!