Glazing

Spraying Glaze: Atomizers, Airbrushes and Spray Guns

Spraying is the best way to get a gradient with no line where two glazes meet, and one of the few ways to put an even coat on a piece too big to dip. It is also the only method that turns your glaze into an aerosol you can breathe. Members do not spray at The Clay Hole, so this lesson is for the people who spray at home. Here is what each tool is for, how to get an even coat, and the rule that is not negotiable.

Members do not spray at The Clay Hole, so this one is for people who spray at home. Thin the glaze, hold it about a foot away, keep the piece turning, and build it in light passes, outdoors or in an extracted booth with a fitted respirator on.

What each tool is actually for Gradients, blends and big pieces One video, and it is not ours
The route that works Where you are allowed to do it Three things that go wrong
An illustrated potter at a spray booth, blowing glaze from a small metal mouth atomizer onto a cream vase with a blue fade on a turntable, her face bare, glaze buckets and shelves of pots behind her
Jump to a section
The rule that is not negotiable What spraying does that dipping cannot The four tools, and what each is for Getting an even coat Knowing how thick it is Gradients, blends and breaking What goes wrong The whole idea, quickly The route that works Three things that go wrong Questions we get asked Keep going

What each tool is for, how to get an even coat, and where you are allowed to do it.

The whole idea

You are building thickness, not covering a surface

Dipping puts a whole coat on in one second and the pot decides how thick it is. Brushing puts a coat on in strokes and the brush decides. Spraying lets you decide, a fraction at a time.

That is the appeal and the difficulty. Nothing stops you at the right thickness. You keep going until you judge it is enough, and a wet sprayed surface looks almost identical at half the right thickness and at twice it.

Which is why the whole technique is about counting passes and checking as you go rather than spraying until it looks covered.

Start to finish

The route that works

Spraying pots with your Mouth Sprayer Paul Randall
  1. Outdoors or an extracted booth, respirator on. Before anything is in the cup. This is not negotiable, and it is not something to do at the studio.
  2. Thin the glaze until it pours like thin cream, then sieve it. A nozzle clogs on the first lump it meets.
  3. Put the pot on a banding wheel so you can turn it without touching it.
  4. Hold the nozzle about a foot back and keep it moving. Standing still in one spot is how runs start.
  5. Spray in light passes, turning the pot steadily, overlapping each pass by about half.
  6. Let it flash off between coats. The surface should lose its shine before the next pass.
  7. Three to five coats, checking thickness with a fingernail as you go.
If it went wrong

Three things that go wrong

You sprayed it far too thin

By far the most common outcome. A wet sprayed surface looks covered long before it is thick enough, and it fires out dry and patchy. Almost everyone underdoes it on their first few pieces.

It ran, or beaded and slid

Too close, too slow, or too many passes without letting the surface flash off. Back up, keep moving, and give it time between coats.

You soaked the pot

Every coat puts water into the bisque as well as glaze. On a thin or large piece, spraying the whole thing in one session can saturate it. Do the inside of the pot one day and the outside of the pot the next.

Before anything else

The rule that is not negotiable

Members do not spray at The Clay Hole. No gun, no atomizer, no exceptions, at any Level. The studio has a spray booth, and only our owners and paid staff use it. Members glaze by brushing, dipping or pouring.

If you spray at home, it happens outdoors or in a properly extracted booth, with a fitted respirator on. Not in a spare room, not in a corner with a window open, not for a quick one.

Every other glazing method keeps the material wet, and wet is the whole reason glazing is a low-risk job. Spraying is the one technique that deliberately turns a bucket of silica and metal colorants into a mist small enough to breathe and light enough to hang in the air for a long time afterward.

  1. A half-face respirator with P100 filters. An N95 is not the right tool for an aerosol you are generating continuously. Check the seal every time, because a beard breaks it. A half-face mask leaves your eyes bare, so wear goggles.
  2. Outside, or in a proper extracted booth. A shared room does not become safe because you are the only one spraying.
  3. The mask stays on until the mist has settled, not until you stop spraying.
  4. Overspray lands on everything. Whatever is downwind gets a coat, so look before you start.
  5. Clean up wet. Dried overspray on a bench is exactly the dust the mask was protecting you from.

Why this one gets its own section

Of the ways to put glaze on a pot, this is the one with a genuine inhalation risk attached. It is entirely manageable, and it is only manageable if the gear goes on first rather than after the first coat.

Why bother

What spraying does that dipping cannot

Dipping is faster, cheaper and easier for most work. These are the jobs where it is not the answer.

Gradients

The thing spraying does best. One color fading into another across a form, with no line where they meet. Dipping gives you an edge whether you want one or not. A sponge can soften an edge, but it still leaves a soft line.

Pieces too big to dip

Anything that will not fit in a bucket, or that you cannot lift wet. Spraying is one of the few practical ways to get an even coat on a large form.

Texture you want to keep

A dipped coat is thick and can fill very fine detail. A sprayed coat is thinner and follows the surface, which keeps a textured piece readable.

Layering without dissolving

A second dip over a dry first coat can soften and lift it. Spray lands dry enough not to disturb what is underneath, so layered effects stay put.

Very thin coats

Some glazes only behave in a thin layer, and dipping cannot reliably go that thin. Spraying can stop wherever you want it to.

Not enough glaze to dip in

Dipping needs a full bucket. Spraying needs a cupful, which matters for a test glaze or an expensive one.

The hardware

The four tools, and what each is for

Spraying Glazes: What Kind Of Spray Gun Do I Need? Marian Williams A short video, under a minute, on choosing a spray gun for glazing.
  1. The mouth atomizer. Two tubes at right angles that you blow through. A few dollars and no compressor. It throws larger droplets that soak into the bisque rather than a fine powdery cloud, which gives a softer, more variegated result. It is also slow, it makes your cheeks ache, and you cannot seal a half-face respirator over a tube you are blowing through, so we would skip it.
  2. An atomizer on a small air pump. The same head connected to an aquarium pump instead of your lungs. Cheap, quiet, endlessly patient, and it puts less glaze into the air than a full spray gun does.
  3. The airbrush. Fine control, small area, and the right tool for detail, for underglaze work and for overglaze. Too slow and too fine-nozzled for covering a whole pot in glaze, and it clogs on anything that has not been sieved.
  4. The spray gun and compressor. A gravity-feed gun of the sort sold for paint. Fast, even, and the only sensible option for large work or for any volume. It also generates the most airborne material by a distance, which is why it belongs in a booth or outdoors.

Which to start with

An atomizer on a small air pump. It costs little, it teaches you what a sprayed coat looks like as it builds, it leaves your respirator on your face where a mouth atomizer cannot, and the variegation it gives is a real effect rather than a compromise. If you find yourself spraying every piece, that is the moment to think about a gun.

Technique

Getting an even coat

  1. Thin the glaze more than you would for dipping, until it pours like thin cream. A glaze at dipping consistency will not atomize; it spits.
  2. Sieve it, every time. Eighty mesh. One lump blocks a nozzle mid-pass and leaves a stripe.
  3. Put the piece on a banding wheel and turn it with your free hand. Reaching around a pot means an uneven coat and glaze on your fingers. Wax the foot first and wipe it clean after, because glaze on the foot welds a pot to whatever it sits on in the kiln.
  4. About a foot back. Closer and it lands wet and runs. Further and it dries in the air and lands as dust that never sticks properly.
  5. Keep the nozzle moving and let the pot turn. Stopping in one place is the single most common cause of a run.
  6. Overlap each pass by about half so the edges of the passes disappear into each other.
  7. Let it flash off between coats. Wait for the wet shine to go matte before the next one, or you are just moving wet glaze around.
  8. Do the inside of the pot in one session and the outside in the next, on anything thin or large. Each coat carries water into the bisque, and a saturated pot stops taking glaze, so the coat sits on top, comes out thin and blotchy, and can slide.
The hard part

Knowing how thick it is

This is the skill. Everything else about spraying is mechanical, and this is the part that decides whether the pot works.

  1. Wet glaze lies to you. A sprayed surface looks fully covered long before it is thick enough to melt into a proper layer. Trusting your eyes is why most first attempts fire out dry and starved.
  2. Use a fingernail. Scratch a line on your test tile, or high inside the pot where it will not show. Never on the foot. You want a layer you can feel, comparable to a dipped coat on a piece you were happy with.
  3. Count your passes. Three to five light coats is the usual range. Counting gives you something repeatable; judging by eye does not.
  4. Write it down. Glaze, number of coats, distance, result. Two lines in a notebook turns one good pot into a method.
  5. Spray a test tile alongside, same coats, same distance, into the same firing. That is the only way to know what a given number of passes actually does.
  6. When in doubt, one more coat. Sprayed glaze goes wrong in the thin direction far more often than the thick one, which is the opposite of dipping.
The fun part

Gradients, blends and breaking

  1. The fade. Spray one glaze over the whole piece, then a second from one direction only, easing off as you go. Where the second thins out, the first shows through, and the transition has no edge.
  2. Dip then spray. Dip the piece in a base glaze for an even, reliable coat, then spray a second over part of it. This is the most useful combination there is, and it removes most of the thickness guesswork. At our buckets it is one dipping glaze per piece and members do not spray here, so this is a home method.
  3. Spraying to make a glaze break. Many glazes change color where they thin over an edge. Spraying lets you thin them deliberately, exactly where the form wants it.
  4. Spattering. Hold further back, or use a lower pressure, and the glaze lands as droplets rather than a mist. Speckled surfaces with no speckle in the recipe.
  5. Masking. Spray suits crisp resist work, because glaze does not pool against the edge the way a dip can. Press tape down well first, and peel tape and latex once the coat is matte.
  6. The atomizer's own look. Larger droplets soaking into bisque give a soft variegation that a fine spray gun cannot produce. Some people prefer it and use the cheap tool by choice.
Read this after a bad one

What goes wrong, and what caused it

Dry, rough, starved surface

Too thin. The most common spraying failure by a distance. More coats next time, and check with a fingernail rather than your eyes.

Runs and curtains

Too close, held still, or coats stacked without drying between. Back up to a foot, keep moving, and wait for the shine to go.

Stripes and banding

Passes that did not overlap, or a pot turned unevenly. Overlap by half and let the banding wheel do the turning.

A gritty coat that brushes off

Sprayed from too far away, so the droplets dried in the air and landed as powder. Move closer.

Spitting and sudden blobs

Glaze too thick, or an unsieved lump in the nozzle. Thin it, sieve it, and clean the nozzle between glazes.

Soggy pot, blotchy coat

Saturated with water from too many coats in one session, so the glaze sits on top and slides. Split the job across two days, the inside of the pot first.

Questions we get asked

The ones that come up at the tables

Can I spray glaze inside the studio?

No, and not outside either. Members do not spray at The Clay Hole at any Level, and only our owners and paid staff use the studio spray booth. Spraying turns glaze into an airborne mist of silica and colorants that hangs around long after you stop. If you spray at home, work outdoors or in a properly extracted booth, and the mask goes on before the glaze goes in the cup.

Is an N95 enough for spraying?

Not really. An N95 is the minimum for occasional dusty work, and spraying is continuous aerosol generation at face height. A half-face respirator with P100 filters is the right tool, and it seals far better.

How thin should the glaze be?

Thinner than for dipping, roughly the consistency of thin cream, and sieved. A glaze at dipping thickness will not atomize properly; it spits and blobs.

How many coats?

Three to five light passes is the usual range, and it depends entirely on the glaze and the distance. Count them, scratch a test line with a fingernail, and write down what worked. Most people spray too thin rather than too thick.

Do I need a compressor and a spray gun?

No. An atomizer on a small air pump costs little and produces a genuinely good result with a softer variegation than a gun gives. A gun is for volume and for large work. Start cheap, and skip the mouth atomizer, because you cannot seal a half-face respirator over a tube you are blowing through.

Why did my sprayed pot come out dry and rough?

Almost certainly too thin. A wet sprayed surface looks covered well before it is thick enough to melt into a proper glass layer, so trusting your eyes is what catches people out.

Can I spray over a dipped glaze?

Yes, and it is the best of both. Dip for a reliable even base, then spray a second glaze over part of it for a gradient. Spray lands dry enough not to lift the coat underneath, which a second dip would.

Why does my pot feel soggy after spraying?

Every coat carries water into the bisque. On a thin or large piece, doing the whole thing in one session can saturate it, which stops it taking glaze: the coat sits on top and comes out thin and blotchy. Spray the inside of the pot one day and the outside the next.

One last thing

Not much money and a lot of patience

Spraying has a reputation as the advanced, expensive glazing method, and the version that produces the nicest surfaces costs very little. An atomizer on a small air pump, a banding wheel and a thinned bucket of glaze will give you fades that dipping cannot touch.

What it asks for is patience with the thickness and discipline about where you do it. Count the coats instead of trusting your eyes, keep a note of what worked, and put the respirator on before the glaze goes in the cup. That last one is the only part of this page that is a rule rather than advice.

Thin it, sieve it, a foot back, keep moving, three to five light coats with drying between. Outdoors or an extracted booth and a P100 respirator, every time, and never at the studio. Most people spray too thin.

If you want the tool comparison, the gradient techniques and the six ways it goes wrong, switch to the Comprehensive Version at the top of the page.