Why Does the Spray Can Spit, Drip or Spray Unevenly?

Short answer

A spray can most often spits, drips or sprays unevenly when it is too cold, not shaken enough, held in the wrong position or when the nozzle is partly dirty. With effect paints containing pigment or fine particles, it is important to shake the can not only before painting, but also regularly during the work.

After painting, it is very important to clear the nozzle. If paint, pigment or fine particles remain in the nozzle or valve, the can may spit, drip or spray unevenly the next time it is used. With paints containing particles, a particle can get stuck in the valve, the can may not seal correctly and pressure or even the contents of the can may escape.

Why does a spray can start to spit?

Spitting happens when the spray can does not produce a fine and even spray pattern, but releases irregular drops or clumps of material. The cause can be pressure, temperature, poor mixing of the contents or the nozzle.

With effect paints, the risk is higher because the paint contains pigments or fine effect particles. These must be evenly mixed inside the can. If they settle or enter the nozzle in a higher concentration, the spray pattern can become uneven.

Most common causes of uneven spraying

• the spray can is too cold,
• the can was not shaken enough,
• the can was not shaken regularly during the work,
• the can is held at an angle, horizontally or in an unsuitable position,
• the nozzle is partly clogged or dirty,
• dried paint from previous use remains in the nozzle,
• with paints containing particles, pigment is stuck in the nozzle or valve,
• no test spray was done away from the painted part before application,
• the can is used at an unsuitable temperature or after long storage in the cold.

A cold spray can has lower pressure and worse atomisation

The temperature of the spray can has a major influence on the result. If the can is too cold, the pressure inside is lower and the material atomises worse. The result can be a rougher spray pattern, spitting, drops or uneven paint delivery.

Ideally, the spray can, painted part and surrounding area should be approximately 20–25 °C. The can should not be heated aggressively on a radiator, with a heat gun or with a flame. It is safer to let it reach room temperature before use.

Shaking only at the beginning is not enough

The spray can must be shaken thoroughly before use, but with effect paints it is important to repeat shaking during the work. Pigments and effect particles can gradually settle inside the can, especially when painting takes longer or when waiting between coats.

If the can is not shaken during the work, the spray pattern can become uneven. At the beginning, a different pigment concentration may come out of the can than later, which can affect the effect, shade and evenness of the layer.

Correct position of the spray can

The spray can should be held as upright as possible during use. If it is used at a strong angle, horizontally or upside down, it may start drawing more propellant instead of an even mixture, or it may deliver paint irregularly.

This can appear as spitting, skipping, dripping or a sudden change in spray intensity. With larger or more complex parts, it is better to divide the work so the can can be kept in the most suitable position.

Why is a test spray important?

Before spraying the actual part, it is always useful to make a short test spray away from the painted surface. This checks whether the can sprays evenly, whether the nozzle spits and whether drops are coming out.

This is especially important after a longer pause, after changing the nozzle, when reusing a can or with effect paints containing particles. One drop or spit directly on the painted part can create a defect that another coat may not hide.

Why must the nozzle be cleared after painting?

After painting, the spray can nozzle should be cleaned. With most spray cans, this is done by turning the can upside down and spraying briefly until only propellant without paint comes out of the nozzle.

This removes paint residues from the nozzle and valve. It is especially important with effect paints that contain pigments or fine particles. If a pigment particle remains in the nozzle, the can may spit, drip or spray unevenly the next time it is used.

With paints containing particles, a particle can get stuck in the nozzle or valve. The can may then not seal correctly, pressure can escape or the contents may start to leak. Clearing the nozzle after use significantly reduces this risk.

What to do if the spray can starts spitting during work

If the spray can starts spitting during painting, do not continue directly on the painted part. First make a test spray away from the surface, shake the can thoroughly again and check the nozzle.

If the nozzle is dirty, clearing it or replacing it with a clean nozzle may help, if one is available. If the can is cold, let it warm to room temperature. If the problem continues, it is better to stop the work than risk a visible defect in the paint.

Extra care is needed with effect paints

With effect paints such as Chameleon, Candy, Pearl or Ghost Pearl, uneven spraying can strongly affect the final appearance. A spit, drop or heavier spot can change the shade, create a patch or make the effect uneven.

That is why correct shaking, regular mixing during work, a clean nozzle, correct temperature and a test spray away from the painted part are especially important with effect spray paints.

How to prevent the problem

• let the spray can reach approximately 20–25 °C before use,
• shake the can thoroughly before painting,
• with effect paints, shake the can regularly during the work,
• hold the can as upright as possible,
• before spraying the part, make a test spray away from the painted surface,
• after a longer pause, shake again and check the spray pattern,
• always clear the nozzle after finishing the work,
• do not store a used spray can with a dirty nozzle,
• if the can starts to spit, do not continue directly on the part.

Summary

• A spray can can spit, drip or spray unevenly because of low temperature, wrong position, a dirty nozzle or insufficient shaking.
• With effect paints, the can must be shaken regularly during the work, not only before painting.
• Before spraying the part, it is useful to make a test spray away from the painted surface.
• After finishing the work, it is important to clear the nozzle so no paint or pigment remains inside.
• With paints containing particles, a stuck particle can cause spitting, dripping, pressure loss or leaking contents.
• If the can starts spraying irregularly, it is better to stop and solve the problem away from the painted part.