If you’re just toying around with a canvas and don’t know what you want to do, then no, your acrylic paint does not need an undercoat.
It may look a little thin, but it isn’t required if you’re just starting out.
If you’re already set on what you want to make, underpainting could be the difference between seeing what you want to see, and having it come up a little short.
Underpainting, or applying an undercoat, adds a layer of depth and various dimensions to a piece.
We’ve all seen pieces of art that appear so complex that we imagine an artists took hundreds of hours meticulously painting every single spec, but art doesn’t have to be laser precise, and often isn’t.
Instead, artists use the tricks and tools of the trade, like underpainting, to their advantage.
Acrylic paint puts you at an advantage, since it can actually have an undercoat.
When you go with oil paints, they take so long to dry that they often mesh with preexisting colors on the canvas.
This doesn’t add the layered effect that you can achieve with acrylic paint. This is how to use underpainting to your advantage, and upgrade every future piece of artwork you produce.
What is Underpainting, and Why is it Important?
Underpainting is used to add layers of dimensions to your painting, both physically and visually.
It makes your paintings look like they’re actual memories or visions from somewhere mystical or far, far away.
Underpainting is when you use an undercoat layer (or several, as we’ll go over in a moment) to create visual depth. It also adds paint layers to your canvas in different areas, which gives a different view depending on your angle.
The main goal in underpainting is to create different layers of depth in your piece, even if you don’t see yourself as the best artist.
You can use underpainting with darker, bolder colors to incite shadow effects, which add another dimension to your painting.
After all, there are people who make their livelihoods off of shading and shadow effects in video games and movie development, because it’s one of the most critical parts in the artistic process that brings your work up a notch.
Underpainting does use a higher volume from your paint stock, but you just have to weigh that against the level of depth and realism that you’re going for.
You’ll also have to have patience in between coats if you want your painting to shine as much as possible.
Speaking of shining, that’s one of the attributes in the first method of underpainting that we’re going to talk about.
There are two separate ways to approach underpainting, each with their own benefits.
This is all about using the tool at your disposal to implement the visual of light throughout your piece.
You’re going to abuse the fact that your canvas is stark white, and intentionally let some of that shine through your painting to provide a brighter piece.
Tonal underpainting uses thinner layers in some areas to let that canvas shine through.
What you want to do is map out the dark and light areas in your painting, once you have the concept that you’re trying to go for. From there, apply the lighter layer first.
Afterwards, you can use your darker paint to cover certain areas that will be shaded.
Because the lighter paint and white canvas is coming through a bit, you will still get the visuals you want, but without making the painting bleak or depressing.
Thin coats, let the canvas shine.
Tonal Ground Underpainting
Maybe your painting is a landscape with a courtyard in the distance, fitted with complex stone walls that add dark and rich color to your piece.
Tonal ground underpainting allows you to make this pop before everything else.
You’re going to start out by painting your white canvas with a dark color, and make the layer fairly thick.
You might even need to add two layers. Lighter colors will have to contest and contrast with the darker color of your choosing.
For instance, using a darker, chocolate brown as your tonal ground underpaint layer could make yellows and blues pop extremely well, giving the appearance that the lighter layer is the reflection of light off the ground or the sky.
It’s all about setting the scene and adding different dimensions without having to trace the outline of a background in the beginning.
How do I Cut my Acrylic Paint?
When you’re underpainting, some of your paints might be a bit too thick.
One thing that’s really powerful is cut your paint using one of the methods we’ve listed below to make layering easier.
Maybe you need to splash a light yellow over 60% of your canvas, but you don’t want it to completely cover the blue undertone paint.
Cut or thin it, and you can achieve more. You can cut your acrylic paint by:
There are pluses and minuses to adding water to your acrylic paints.
For one, it does thin out your paint effectively, but you literally have to use one drop of water at a time.
Your acrylic paint isn’t supposed to be mixed with water, so gradually adding in very small amounts is going to thin it out, but it will also force it to lose its strength.
Adding too much water will completely ruin your paint, so it’s important to take this advice with a grain of salt.
If this is a bit too risky for you, we have an alternative option listed below. If you choose to do this, use filtered water.
There’s something in tap water called dissolved solids, and while some of them could be minerals that are good for you, there’s also the presence of chlorine and other compounds.
Those aren’t going to mix well with your paint, and can cause oils to separate.
Mixing With a Palette Knife
You’re basically going to aerate your acrylic paint with this method.
Use a palette knife and make sure that it’s scraping the bottom of your container.
Whip the paint around at a medium pace for about seventy-five strokes.
If the container is large (usually over twelve ounces), up the stir count accordingly.
Your goal is to get a whipped consistency that might even look a little bit lighter than it did before.
You’ve incorporated oxygen into the paint, and while this effect isn’t going to last long, it will last long enough for you to paint onto your canvas or glass.
Treating it With Polymer Compounds
You can use just about any polymer compound on the market to thin your paint out, or a full-fledged acrylic paint thinner.
Paint has a certain amount of polymer in it, which is what makes it acrylic in the first place.
If you’ve ever seen acrylic glass, that’s a form of plastic made from synthetic polymer compounds, most of which are in your paint.
The polymer in acrylic paint thinner is clear, so it keeps the paint strong while diluting the color by the desired amount.
This is the best way to dilute your paint without losing color or strength.
Adding White Paint
It’s not actually going to thin it out, but it will dilute the color enough to give you the desired look.
This can work well for lightening colors and making them shine through better when there’s a darker underpaint layer.
How do I Thin Applied Acrylic Paint?
Once the paint is on your canvas, you don’t have much time to cut it before it’s blended into the cotton.
This method isn’t recommended, because you get a much more even coloration and consistency if you thin your acrylic paint before you apply it.
That being said, just because this method isn’t recommended doesn’t mean you can’t do something awesome with it.
You can use a bit of turpentine to thin out the paint once it’s on the canvas in order to give a distressed and warped look.
There’s no rules in art; go crazy and do what you want to make your vision come to life.
Keep in mind that turpentine can separate your paint a bit, and in some cases it could make it run a little bit.
The best way to do this is by putting on some gloves, and balling up a paper towel. Dip one end of it into the turpentine, and gently blotch it onto the canvas.
This gives that distressed look we were talking about earlier, but it also keeps it controlled so that you’re not damaging your canvas or undoing your work.
Get to Mastering Your Canvas
Underpainting means that it could take longer to achieve your end goal, but it could look ten times better than you imagined when you get there.
Exploring this method of painting with acrylics is an absolute ton of fun, and will certainly keep your interest.
Consider this getting an upgrade in your acrylic painting skills.