Spray Paint Caps and Can Pressure for Stencils

So much of what’s known and the standard applications for spray paint materials is obscured by jargon. Here’s a breakdown on caps and can pressures for the rest of us. If you’re in a hurry and just want to know what kind of can and cap to buy to use with your stencil, it’s easy:

High-pressure can with default (medium) cap works fine for most stencils.

But if you’re out with your stencils and you think you might freestyle a bit, here’s a little more information. Understanding how your paint is going to come out comes down to three basic things: cap width, cap shape, and can pressure.

Cap Width

  • ‘skinny’ (narrow) caps have a narrow angle of spray and are good for outlines and sketches
  • ‘fat’ (wide) caps are good for filling in large areas, and also for making gradients
  • medium caps are between fat and skinny

Cap Shape

  • round are much more common
    • good for line work and round shapes
    • doesn’t matter which way it’s turned, because it’s round
  • flat are good for calligraphic effects and even coverage (side to side)
    • also good for ‘knife’ work to cover bridges for example
    • good for gradients because it’s easier to make planar shapes
    • you need to be aware of what the orientation of the outlet is, so you know whether you’re spraying vertical or horizontal–the tips on these caps can usually (but not always) be turned a full 360 degrees

Most cans come with a medium round cap by default, so you don’t need to buy any of these. Instead, buy a round skinny cap and both flat and round fat cap in order to have variety when you need it.

In a hurry?

High-pressure can with default (medium) cap works fine for most stencils.

Can Pressure

  • High-pressure gives you more paint per time
    • great for covering large surfaces quickly
    • can drip if you don’t work fast enough
  • Low-pressure gives less paint per time
    • great for detail work, or any time you want to move more slowly
    • covering with low pressure cans can look spotty or blotchy

You’re more likely to pair a narrow cap with a low pressure can, and a wide cap with a high pressure can. The reason is that, if you put a narrow cap on a high pressure can, you’re going to have to move very fast in order to avoid drips. And if you put a wide cap on a low-pressure can, you’re going to have to wait a long time to cover a wide area.

On the other hand, if you want to make a long, fast, straight, fat line, that’s when you put a thin cap on a high pressure can. (That’s the secret of getting a straighter line: go faster.) And if you want to make a subtle, diffuse effect and control how much paint is getting to the surface, you can put a wide cap on a low pressure can.

Most cans come with a medium round cap by default, so you don’t need to buy any of these. Instead, buy a round skinny cap and both flat and round fat cap in order to have variety when you need it.

That’s the taxonomy, and any supply shop will know what you mean when you say ‘I need a fat cap and a skinny cap’. But the different manufacturers love to come up with their own special effects and names, and painters with endorsements of course have to have a point of view about the intricacies of the various caps. Here’s a guide from a balanced vendor, showing a variety of caps with their cool names. But just remember: fat cap and skinny cap.

How Does Cap Width and Shape, and Can Pressure Affect Your Stencil Work?

How does all this relate to stencils? When you first lay a stencil down, you just want to cover it quickly. You don’t need thin lines because the stencil is taking care of the line element for you. So you use a medium or wide cap with high pressure can, mostly. And in that case, the cap that comes with the can is often just fine. Medium caps cover small stencils pretty quickly.

However, sometimes you’ll want to ‘glaze’ certain regions of a stencil. For example, you want to use white to create a ‘shine’ element. For that, you can either use a low pressure white can with medium cap, or you can use a wide cap with high pressure can. But since you most often use this effect with white, it makes sense to have a low pressure white can.

Tip: low-pressure cans are just high-pressure cans with less propellant in them. So you can invert a high-pressure can and hold down the cap for a minute or two to get a lower pressure can. Keep in mind, when you do this, that you can’t get the high pressure back again once you do this: it will stay a low pressure can until it’s done. (You may also find that the valve gets stuck more easily after you use it this way.)

That’s it!