Whether you are working with oils or acrylics, your surface needs to be primed before you begin. This greatly extends the life of your art by ensuring it will adhere to its canvas support and not flake or crack off. In these pictures I’m using unstretched canvas (read how to stretch canvas here), but the process is the same if you are using an unprimed stretched canvas, just be sure to prime the edges too. This technique can also be used to prep thick paper for painting or mixed media work.
You’ll need gesso to prime the surface. Utrecht’s acrylic gesso is my favorite and the only kind I use. I like it because it’s super thick and very opaque, so it coats the surface well and you can use it to add texture if desired. This gesso (as with all acrylic-based gessoes) can be used under either acrylic or oil paintings. There are some gessoes that are made only for oils, but I prefer the acrylic type because of its versatility.
To begin priming your raw canvas, the first few coats of gesso need to be diluted so the canvas fibers can absorb the primer and create a strong, impermeable support for your painting. I dilute my gesso with a ratio of about 1 part water to 2 parts gesso. I like the consistency to be liquid and pourable. Utrecht gesso out of the bucket is so thick, it requires quite a bit of water to make it pourable. If you are using a different type of gesso you may not need to add as much water. Most gessoes available in craft stores are already very thin, so use your best judgment.
Use a large flat brush to apply the gesso to the raw canvas. As you brush the gesso in, follow the fibers of the canvas, working horizontally and then vertically. Apply an even coat, and let each coat completely dry before adding another. Use at least two coats of the diluted gesso. Once these initial coats have dried, add a layer of gesso at full strength. You can either brush this on evenly for little or no texture (ideal for painting things like portraits where you want a smooth surface) or you can intentionally add texture with brushes, palette knives, or any other tools. I personally like the textured look for abstract paintings. I find it helps give dimension to the painting, and I like to use the texture as part of the composition. Again, this thick texture is only achievable with heavy-bodied gessoes like those by Utrecht. Once this final layer of gesso is dry, you can begin your painting.