# One swapped nozzle decides every line you're about to paint

> A spray can is fixed; the cap on top of it is the instrument. Fat or skinny changes the width of every stroke, and the choice is made before the first one.

August 20, 2026 · https://justog.club/stories/fat-cap-skinny-cap

Five nozzles across the chest, each a different shape. Under every one, a single stroke — the
line that cap actually makes, from a wide soft band on the left to a fine hard mark on the right.

The can never changes. The cap is where the decision lives.

## Why does the cap matter more than the can?

Because the paint and the pressure are fixed, and the nozzle is the only variable left.

A can holds one paint at one pressure. Every writer working from the same can is starting from
the same material. What changes the outcome is the aperture the paint leaves through, and that's
entirely a function of the cap screwed onto the top. Swap it and the same can produces a
different tool.

That's a narrower kind of control than
[a mop or a marker gives on paper](/stories/the-mop-and-the-ink) — you can't blend two
caps mid-stroke — but it's a real one, and it's made before any paint hits the wall.

## What's the actual difference between fat and skinny?

A fat cap lays down a wide line with a soft edge; a skinny cap lays down a fine, harder one.

Fat caps push more paint through a wider opening, which is why they cover ground fast — a fill or
a background goes down in a fraction of the passes a skinny cap would need. The trade is edge
quality: a fat line spreads slightly as it leaves the nozzle, so its border is soft rather than
crisp.

A skinny cap restricts the opening, so less paint comes out and it comes out straighter. That
makes it the tool for outline, detail and anything that has to read as a hard line rather than a
band of colour. It's slower for the same reason it's precise.

### Why the choice can't be corrected mid-stroke

Once a stroke starts, its width is set. There's no way to thin a line that's already fat, and no
way to widen one that's already skinny without going back over it and changing what it is. That's
different from a pencil, where pressure can vary the mark as you go. A spray line's width is
decided at the cap, before the arm moves — which is closer to
[choosing the outline weight before you draw](/stories/outline-fill-and-forcefield) than
to varying a stroke as you go.

## Does a wide line mean less control?

No — a soft edge on a fat cap is a property of how the spray leaves the can, not a sign the
writer wasn't careful.

Fine mist particles at the edge of a wide spray settle a little beyond the main line, which is
what produces the soft border. A skinny cap does the same thing at a smaller scale; it just looks
harder because the whole line is narrower. Neither cap gives a perfectly geometric edge, and
asking one to would be asking spray paint to behave like a ruled pen.

Where the drip is a genuinely accidental artefact turned deliberate, described in
[the piece on doing it on purpose](/stories/drips-on-purpose), the soft cap edge was
never an accident to begin with — it's just what the tool does.

## Who owns a cap like this?

Nobody — the nozzle is hardware, and the line quality it produces is a physical fact about
aerosol paint rather than anyone's invention.

What would need permission is a specific writer's piece reproduced from a photograph, and that
permission doesn't evaporate just because the wall was painted without the owner's consent.
Painting something illegally doesn't remove the painter's copyright. In the US, VARA — the Visual
Artists Rights Act, a 1990 amendment to federal copyright law — protects works of "recognized
stature" from destruction and protects the artist's right to be named, even on somebody else's
property. A diagram of five nozzles and the strokes they leave copies no one's actual work, which
is a simpler position to be in.

## Does it print well?

Very — this design is already thinking in flat colour and controlled edges before it gets to
fabric.

Five nozzles in one ink and five strokes that go from soft to hard translate cleanly: the soft
edge is a gradient of density rather than a fine blended tone, and fabric can hold that as a
solid shape with a feathered border, which is a different thing from asking it to reproduce a
smooth gradient. Deep red on pale grey keeps the contrast high enough to read the whole row at a
glance. One ink, kept flat, is the right call here — a second colour would compete with the
strokes for attention rather than support them.

## How do I get one made?

Describe the tool or the line at [JustOG](/) — how many nozzles, which colour, how sharp the
strokes should run from wide to fine. Pick a direction, drag the crop frame, see it composited on
the real garment, and it's made to order and shipped.

Designs other people have published are in the [shop](/shop).

Every line on that chest was decided before the can was even shaken.