More than just about any other topic, gesso is what I'm asked about the most: Why did you use gesso? Why didn't you use gesso? How do you apply gesso? How many layers of gesso should I apply? What kind of gesso should I use? Do you have to sand gesso? Why are there different colors of gesso? How do I know if I need to add gesso? For such a simple and often overlooked medium, it sure generates a lot of confusion! Let's clear up that confusion, shall we?
What is Gesso, Anyway?
Gesso used for acrylic paint is an acrylic polymer medium, or paint binder, that’s mixed with chalk or calcium carbonate. This gives the gesso its dry, toothy texture. Sometimes, paint pigments are mixed in, typically white or black, but any color can be added at the artist's discretion to create absorbent, colored grounds. Gesso can also be purchased in a clear formulation. Don't let that make your head spin! We'll talk about that in a minute, too.
Gesso is used to create a surface that is ready to receive paint. This is because not all surfaces you might want to paint on will hold paint, and some are so absorbent that painting on them would be very difficult. Adding a layer or two of gesso can make surfaces like wood, stone, plastic, glass—and yes, canvas—ready to receive your paint. Without gesso on these surfaces, the paint might absorb too deeply into the materials (wood and canvas). It might bead up on the materials and not stick at all (glass, to an extent, and some plastics). Or it might just flake off over time.
Not only does gesso prepare a surface to receive paint, but it can help even out the texture of a surface to achieve a smooth, consistent paint application. But how do you apply the gesso? Any way you like!! I love to experiment with gesso. Sometimes I'll apply it very thin and smooth, sometimes very thick with lots of texture, sometimes with a brush, and sometimes with a palette knife. Sometimes I even mix it with other mediums such as Liquitex's Flexible Modeling Paste for a highly absorbent and textured surface that's very similar to painting on smooth stone or old plaster. You can even mix it with paint to reduce the dry, toothy texture and to add color (gesso and underpainting color all in one!). There is no right or wrong way to apply gesso! Experiment and see what you think. Do you like the texture you get from applying gesso heavily with a palette knife, or do you prefer a smooth, even layer applied with a brush and then lightly sanded? Which brings me to another topic that needs some discussion: sanding.
Why Do You Sand Gesso?
There are a couple of reasons why you’d want to sand gesso after it’s dried. Neither of these reasons are good enough reasons for me to bother doing it, but I know some people who swear it's the only way to go! First, very lightly sanding the gessoed surface smooths it out and reduces that ultra-toothy texture. It can also completely eliminate canvas texture that might still show through the gesso. Me? I'm a texture gal. I love that rough surface, so I never sand it off.
Another reason to sand gesso is because its rough texture can damage your brushes over time. It kind of acts like sandpaper when you run a brush over it. I'm already pretty brutal on my brushes, and I believe that using a brush however I need to get the results I'm looking for is much better than being nice to a brush. As a result, I'm much more likely to destroy my brushes long before gesso does. But if this is a concern for you, just take a very fine sandpaper and lightly run it over the surface of the gesso. It really doesn't take much effort. In fact, applying the gesso in the first place probably takes more effort than sanding it.
How Many Layers of Gesso Do I Need?
This is up to you! I usually don't do any more than one layer unless I'm really trying to build up some interesting texture, and even then I'll probably only add one layer and mix it with Flexible Modeling Paste. I've had people tell me in the past that they've been super frustrated that it took several layers of gesso to completely cover an old painting. You don't need to waste your time and build frustration adding layer upon layer of gesso to an old painting! It’s ok if you can still see the old painting, because one generous layer will be enough to prep the canvas so the new painting will easily cover the old one. Gesso, in my experience, is pretty translucent, because it's mostly a chalky powder in a binder. If you're really concerned about completely covering an old painting, either use black gesso, tinted gesso (some companies make gesso in a million colors!), or put down your layer of gesso and then do an underpainting for your new painting. We've talked about underpainting a ton in the past. You can check out these videos HERE, HERE, and HERE for more information. I’ll probably write a blog post about underpainting sometime soon, as it’s another topic that seems to confuse a lot of people.
What’s the Best Kind of Gesso to Use?
It all depends on what you like and what you're using it for! There is not a single gesso that's right for everyone. It's completely subjective. I advise that you try several brands of gesso and decide what you like the best. Some are smoother and less toothy. I know a lot of people like these, but I don't. If I'm gonna use gesso, I want my surface to be rough and textured! Why? Because that's what I like. Simple as that.
What is Clear Gesso Used For?
Let's say you really want to paint on a sheet of glass, or maybe a beautiful stone surface, or even add elements to a painting you've already done. Obviously, if you use regular gesso on glass, you're just going to lose the transparency of the glass. Using white gesso on that beautiful stone is going to obscure the beautiful colors, and you can't just paint over that painting! These are times you'd want to use clear gesso. All of the tooth, but none of the color! Yay! Or, mix it with a color of paint to instantly turn it into colored gesso!
How Do you Know if You Need to Add Gesso?
There are two highly complex answers to this question. Ready?
If the paint will not stick to the surface you want to paint on.
If you want to.
Ok, so the answers aren't that complex, but let's spend a minute on each.
First, ask yourself if the paint will stick to the surface you want to paint on. If you're wanting to paint on a surface not actually meant to be painted on, you’ll probably want to add gesso. But what about canvas?! If you buy commercially prepared canvas, guess what? It's already gessoed!! Don't believe me? Check this out. The first photo is a canvas still in the package. See how white it is on the front and how tan it is on the back? That's because the back is the actual canvas fabric without gesso on it. The front is gessoed!
See this next photo? This is a canvas where—for one reason or another—all of the paint and gesso has peeled off. This is just the raw canvas with nothing on it. You can tell because it's very thin and transparent (no, this is not a Blick canvas. This was another brand whose quality isn't as on point). If I were to try and paint on this surface, my paint would squish though the other side and probably absorb into the fibers.
So, ok: If a canvas you purchase is already gessoed, why does it need another layer of gesso before you can paint on it? Well, it doesn’t actually need another layer. It’s ready to go! This is why a lot of people, including me, don't always (or maybe never) gesso a canvas. So that goes back to...
Gesso if you want to. If you want to change the texture, smooth out the canvas, or maybe rough it up more (maybe you just hate the texture of the factory gesso), you might decide to add a layer (or five) of gesso. Or not. There is not a right or wrong answer here! I know that sometimes people will tell you that THIS is the right way and it should ALWAYS be done this way, but really, you can do anything you like. YOU are the artist. YOU make the decisions for your art. Just because someone else would do it different doesn't mean you can't do it the way you want to.
Conclusion: The TL;DR Version
Gesso prepares your surface to receive paint. Commercial canvases that you buy are already gessoed at the factory. You can add gesso (or not) in any way you like, for any purpose you like, in as many layers as you like, sanded or not, in any color you like, no matter what anyone else says. This is your art. Do it how you like. But experiment. You might try gesso and hate it. But over time, you might find yourself using it more and more. That's certainly where I am right now. I probably gesso 90% of the canvases I use for my personal art. It's just something I've noticed I'm doing more and more, and it's simply because I like the texture. No other reason.
I hope this helped clear up some confusion about gesso. Now go do that experimenting and decide what you like best!