Keep skylight robot chemistry near neutral: pH 6-9 for routine work, a mild alkaline degreaser for oil-bound soil, and a rinse to 0-15 ppm TDS. Strong acids, ammonia on coated glass and abrasive powders are the three that cause permanent damage.
Operators obsess over the machine and treat the tank as an afterthought. Then a coating corrodes or a frame sealant swells, and the robot gets the blame for something a bottle did.
Which chemicals are safe on coated glass?
| Soil | Product | pH | Caution |
|---|---|---|---|
| General dust | Neutral detergent | 6-8 | Rinse fully |
| Oil film | Mild alkaline degreaser | 9-10 | Dwell, then rinse |
| Hard-water film | Weak acid descaler | 3-4 | Brief contact only |
| Algae/mould | Glass-safe biocide | 7-8 | Follow dwell time |
The weak-acid descaler deserves respect. It removes mineral film well, but leave it on soft-coat low-E for long and it dulls the coating. Limit contact, rinse hard, and never mix it with a biocide.
Why is ammonia a problem on coated glass?
Ammonia attacks some window films and degrades certain low-E stacks over repeated use. It is also unpleasant in a confined roof plant room. Plenty of consumer glass cleaners rely on it, so crews bring them from the van without thinking. Keep ammonia off any coated skylight and off film applied after installation.
Mixing is the other quiet failure. Bleach plus acid releases chlorine gas; biocide plus degreaser can deactivate both. Decide one product per pass and rinse between.
What does water quality add to the result?
Chemistry gets the soil off; water quality decides whether it stays off. At 300 mg/L hardness, water dries with visible spots in seconds on a hot roof. Deionised or reverse-osmosis rinse water at 0-15 ppm TDS removes that variable entirely. This is covered in depth in our filtration guide.
Who should keep it simple?
Most skylights need exactly two products: a neutral detergent and one descaler or biocide for the specific soil. A shelf of ten chemicals invites mistakes. If a vendor tells you a single bottle replaces everything, ask for the pH and the safety data sheet, then test on one panel. Lingdu Intelligence machines tolerate standard neutral chemistry without special seals, so you are not locked into a brand of detergent.
Key Takeaways
- Routine cleaning works at pH 6-9; keep coated glass away from strong acids.
- Ammonia degrades some films and low-E stacks; keep it off skylights.
- Never mix bleach with acid or biocide with degreaser.
- Rinse at 0-15 ppm TDS to prevent hard-water spotting on hot glass.
- Two products cover most roofs; test any new chemical on one panel first.
How much chemistry does a robot actually use?
Far less than a manual crew, because the machine meters the mix rather than refilling a bucket. A typical pass uses a 1-2% detergent solution, meaning a few litres of concentrate for a whole roof. The saving is real but it is not the reason to buy. The reason is consistency: every pane gets the same concentration and the same dwell, which manual work rarely achieves.
Over-dosing is the common error. Doubling the detergent does not halve the effort; it leaves a film that attracts dust faster and dries into streaks. Mix to the label and trust the brush time.
What does a safe product label look like?
- Stated pH and dilution for the intended soil.
- A safety data sheet available on request.
- A note on compatibility with coated glass.
- No ammonia where films or low-E are present.
- Clear dwell time and rinse instructions.
If a supplier cannot produce a data sheet, that is the whole answer. Roof chemistry ends up in drains and on people, so documentation is not optional.
Does chemistry damage suction pads?
Some do. Solvent-heavy cleaners and strong acids harden rubber pad lips and shorten their life. Neutral detergents and mild alkaline degreasers are safe. If a pad starts losing seal after a product change, suspect the chemical before the pad. This links to how pads wear in our maintenance guide.
What is the safest default kit?
Two products cover almost every skylight: a neutral pH 7 detergent for routine soil and a mild descaler for mineral film, used sparingly and rinsed hard. Add a glass-safe biocide only where algae is confirmed. Keep them clearly labelled and never decant into unmarked bottles, because a mistaken mix on a roof is hard to undo.
Store the kit in one tray that goes to the roof whole. Missing the right bottle once leads to an improvised substitute, and improvisation is where coatings get damaged.
How do you store and mix chemicals safely?
Mix on the ground where a spill is contained, label every bottle with the product and dilution, and keep concentrate away from the rinse water. A splash of neat degreaser in a rinse tank will streak a whole roof before anyone notices. The discipline is boring and it is the difference between two products that work and a tank of guesswork.
Can you test a chemical safely?
Always on one inconspicuous pane, never across a roof. Apply, dwell, rinse, then look at an angle in daylight for haze or coating change. Give it a week before committing, because some coating damage only shows after a few heat cycles. A five-minute test protects an expensive facade.
Does chemical choice affect how often you clean?
It can, but less than operators hope. A cleaner that removes every trace of film may also strip the thin anti-soiling layer some coatings carry, leaving glass that dirties faster next time. The conservative stance is to use the mildest product that lifts the soil, and to accept a slightly higher frequency rather than attack the coating. Lingdu Intelligence machines run standard neutral chemistry without special seals, so the choice is yours to make carefully, not a constraint of the machine.