Glazing

Spraying Glaze: Atomizers, Airbrushes and Spray Guns

Spraying is the only application method that gives you a gradient, and the only one that puts an even coat on a piece too big or too textured to dip. It is also the only one that turns your glaze into an aerosol you can breathe. Here is what each tool is for, how to get an even coat, and the rule that is not negotiable.

Thin the glaze, hold it about a foot away, keep the piece turning, and build it in light passes. Spraying happens on the outside tables with a fitted respirator on, because you are making the glaze airborne.

What each tool is actually for Gradients, blends and big pieces Two videos, neither of them ours
The route that works Where you are allowed to do it Three things that go wrong
A potter spraying glaze onto a pot turning on a banding wheel, wearing a respirator
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. Outside tables, respirator on. Before anything is in the cup. This is not negotiable.
  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 outside one day and the inside the next.

Before anything else

The rule that is not negotiable

Spraying glaze is done on the outside tables, with a fitted respirator on. Not in the studio, 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.
  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 everything in the glaze room, this is the technique 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 only spraying does. 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.

Pieces too big to dip

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

Texture you want to keep

Dipping floods carving and fills fine detail. A sprayed coat sits on the surface and follows it, which keeps a textured piece readable.

Layering without dissolving

Dipping a second glaze over a dry first coat softens and lifts 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 Short and to the point on matching the gun to the work, which is the decision most people get wrong first.
  1. The mouth atomizer. Two tubes at right angles that you blow through. A few dollars, no compressor, and the tool most people should start with. 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 and it makes your cheeks ache.
  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

A mouth atomizer, honestly. It costs almost nothing, it teaches you what a sprayed coat looks like as it builds, 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.
  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. Outside one session, inside the next on anything thin or large. Each coat carries water into the bisque, and a saturated pot can crack or slump.
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 somewhere that will not show, like 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.
  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 is the method that makes crisp resist work possible, because nothing floods under the tape the way a dip does.
  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.

The pot cracked or softened

Saturated with water from too many coats in one session. Split the job across two days, outside first.

Questions we get asked

The ones that come up at the tables

Can I spray glaze inside the studio?

No. Spraying turns glaze into an airborne mist of silica and colorants that hangs around long after you stop. It happens on the outside tables with a fitted respirator on, 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. A mouth atomizer costs a few dollars 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.

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 risks cracking or softening. Spray the outside one day and the inside the next.

One last thing

A few dollars and a lot of patience

Spraying has a reputation as the advanced, expensive glazing method, and the version that produces the nicest surfaces costs about as much as a sandwich. A mouth atomizer, 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. Outside tables and a P100 respirator, every time. 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.