Three variables produce a frosted surface: abrasive grit size, working pressure, and how long any point on the glass is exposed. Grit is covered in the grit size chart. This page is about the other two — and about the air supply behind them, which is where most frosting problems actually originate.
The working pressure range
Our vertical and horizontal machines run at 0.6 to 0.8 MPa — roughly 87 to 116 psi. That is the operating range the equipment is built around.
Within that range the relationship is straightforward:
- Higher pressure — each particle strikes harder. Faster cutting, more aggressive surface, more stress on the mask, faster nozzle wear.
- Lower pressure — gentler cut. Slower, kinder to the mask and to fine detail, longer nozzle life.
Pushing pressure up is the instinctive fix when frosting looks weak. It is usually the wrong one, for reasons covered below.
The variable people forget: air supply
This deserves its own section because it causes more disappointing results than pressure setting, grit choice, and film selection combined.
A sandblasting machine consumes compressed air continuously while blasting. If your compressor and receiver cannot sustain that demand, pressure sags mid-cycle. The gauge may read correctly at the start and drop as the cycle runs.
What insufficient air looks like on the glass
- Visible banding — lighter and darker stripes across the panel
- Frost that is even at the start of a pass and weaker toward the end
- Results that vary between the first panel of the day and the tenth
- Inconsistency that does not respond to changing grit or film
If your frost is uneven and changing the abrasive did not fix it, check your air before you change anything else. People replace media, change film, and blame the machine while the actual problem is a compressor that cannot keep up.
What to check
- Compressor output against the machine’s stated air consumption — with margin, not exactly matched
- Receiver tank capacity, which absorbs demand spikes
- Line size and length from compressor to machine; long or undersized runs cause pressure drop
- Moisture separation and drying — wet air causes clumping in the abrasive and inconsistent flow
- Filter and dryer condition, which degrade quietly over months
Moisture deserves emphasis. Damp abrasive flows unevenly and clogs, and the symptom looks like a machine fault rather than an air quality problem. In humid climates this is a maintenance item, not a one-time setup item.
Travel speed and exposure time
The third variable is how long any point on the glass is under the abrasive stream. Slower travel means longer exposure means deeper cut.
This is the variable to adjust first when a result is close but not right, because it is the one that changes nothing else. Raising pressure changes cut depth, mask stress, and nozzle wear all at once. Slowing travel changes cut depth and cycle time only.
Reference productivity on a vertical machine is around 25 m²/h, but that figure moves substantially with pattern, media, and settings. Treat it as a planning number.
Nozzle condition — the silent drift
Nozzles wear. The orifice gradually enlarges, which lowers velocity at the same supply pressure and reduces air efficiency.
The problem is that it happens slowly. Nobody notices a bad day; they notice that results are somehow not what they were six months ago, and by then the operator has quietly compensated by raising pressure — which accelerates wear on everything else.
- Check nozzle condition on a schedule, not when something goes wrong
- Keep spares so a worn nozzle is replaced rather than tolerated
- If pressure has been creeping up over months to maintain the same result, the nozzles are usually the reason
- Nozzle-to-glass distance and angle also affect the result — establish them as fixed settings rather than things an operator adjusts by feel
How to find your settings
There is no universal table, and any supplier who gives you one is guessing about your air supply, your glass, and your media condition. There is, however, a reliable method.
- Fix your grit and your film. Change one thing at a time.
- Start at the low end of the pressure range with your normal travel speed.
- Blast a test panel. Assess it under the lighting your customer will see it in — not shop lighting.
- If the frost is too light, slow the travel speed first. Re-test.
- Only if travel speed alone cannot get you there, raise pressure in small steps and re-test.
- When you have a result you are happy with, write the settings down — pressure, travel speed, grit, film, nozzle distance — and treat that as your standard for that product.
The reason for adjusting travel speed before pressure is that the lowest pressure that achieves your finish is always the right one. It gives you the longest nozzle life, the least mask stress, and the most margin when something drifts.
Common problems and where to look first
| Symptom | Most likely cause |
|---|---|
| Banding or stripes across the panel | Air supply sagging mid-cycle |
| Frost weaker at the end of a pass than the start | Air supply, or receiver tank too small |
| Results drifted worse over months | Nozzle wear, or spent abrasive |
| Ragged pattern edges | Grit too coarse or film too thin for the blast — see the thickness guide |
| Mask lifting at edges | Poor lamination, or blast pressure too high for the film |
| Abrasive flow surging or clogging | Moisture in the air line |
| Cycle times slowly increasing | Abrasive rounded off and needs replacing |
| Frost uneven panel to panel | Operator adjusting settings by feel rather than to a written standard |
Write your settings down
The single highest-return habit in a frosting shop is recording the settings that produce each product and treating them as a specification rather than a starting point. It makes results repeatable, makes training possible, and turns drift into something you can detect instead of something you discover from a customer complaint.
Setting up a new machine
If you are commissioning a machine, tell us what you produce and we will give you a starting point for your configuration and media rather than leaving you to find it by trial. Installation, commissioning and troubleshooting support is part of what we supply — see warranty and support.
Get in touch. We usually reply within one business day.