What is overspray, and which faces will it reach?

When we spray a finish onto a part (primer, paint or a clear topcoat), a little of the fine mist drifts past where it’s aimed, and the drift that settles on surfaces you wanted left unpainted is called overspray.

The short answer: leaving a face (one surface of the part) unpainted is not a promise of zero paint. An open face beside the painted area can catch a light haze, while the depth of a recess, faces pointing away and anything we mask usually stay clean; if haze lands where it shouldn’t, we sand it back, or redo the part if it won’t sand back cleanly.

Why an unpainted face can still catch paint

Painting is priced by the surface area we coat, so the faces you ask us to leave unpainted come off the price (how finishing is priced). But leaving a face unpainted only means we don’t aim at it. It can’t change where a fine mist travels, which is one of the limits of any sprayed finish.

Whether an unpainted face stays clean comes down to one question: could the mist reach it?

Faces that can catch overspray

• Flat, open faces right beside a painted area
• Faces angled toward the spray
• Shallow steps, rounded corners and edges close to the painted area

These don’t get a full coat, just a haze of the colour, from barely visible to a clear fade like the one below.

Faces that usually stay clean

• The depth of recesses, pockets, internal channels and round holes (the mouth can catch a little)
• Faces pointing away from the spray, the back of the part
• Anything we mask off with tape or a plug

Threads, holes and faces that fit together

Some unpainted faces matter more than others. A thread, a bolt hole or a face that has to sit flat against another part can’t take even a thin coat: paint adds a layer of its own, enough to stop a screw turning, a pin seating or a lid closing. We plug holes and tape the faces that fit against another part whether or not overspray would ever reach them.

How to mark what stays unpainted

Circle the faces that stay unpainted on a screenshot or photo of the part and send it with the file. The instant quote prices paint over the whole part, so we quote it for you with those faces left out. Say which of them fit against another part, so we protect those first. We check every part before we start, and if a face won’t come out the way you marked it, we tell you before any work or payment goes ahead.

What we do about overspray

We mask what has to stay unpainted and turn the part on the bench so the spray travels away from it. On simple shapes that gives a clean line. On intricate parts a faint haze on an open face can’t always be avoided. If it lands where it shouldn’t, we sand it back. If it won’t sand back cleanly, we redo the part, so the part you collect is one you’re happy with.

Not sure how your part will behave? Talk to us about the paint