What is SiO2?
Quick answer: SiO2 (silicon dioxide) is the backbone of most ceramic coatings. It is a glass-forming compound that bonds to your car's clear coat at the molecular level, creating a hard, hydrophobic layer. The raw material is essentially refined sand; the formulation is what gives it performance.
It's also the backbone of most ceramic coatings. The raw material isn't expensive -- but turning it into a coating that cures cleanly, bonds to the clear coat and performs for years takes proper formulation.
Although silica is essentially sand, in certain engineered forms it becomes highly hydrophobic, which is what makes it so useful in water-repellent coatings.
People often use silicon, silica (SiO2) and silicone interchangeably -- they're not the same thing. Our coatings are built on silica / SiO2 chemistry that bonds to the clear coat and cures into a hard, glass-like network. Some formulas also use organosilicone resins (siloxanes) as modifiers. Those don't turn the product into "just silicone" -- they tweak how it behaves: extra slickness, stronger water beading, better spread and self-levelling during application, without replacing the underlying SiO2 backbone that delivers durability and chemical resistance.
It's also why supermarket "ceramic" sprays feel so slippery: many lean heavily on silicone polymers for fast gloss and water behaviour. Nothing wrong with that as a topper, but it isn't the same as a true nano-ceramic that cross-links with the paint. One practical note: fresh, uncured silicones can cause fisheyes if you're about to paint a panel, which is why bodyshops are wary of the word "silicone". A fully cured ceramic coating is different -- it's inert and stable. If a panel ever needs repainting, we simply decontaminate and mechanically prepare it as usual. In short: SiO2 gives the hard, long-term protection; silicone components, when present, fine-tune application and feel -- they don't replace the ceramic.
How SiO2 behaves inside the coating
- Forms the backbone -- the SiO2 content is what turns the liquid coating into a solid, glass-like film once cured.
- Bonds to the clear coat -- properly prepared paint lets the SiO2 network anchor into the microscopic peaks and valleys of the clear coat.
- Creates a smooth surface -- as it cures it levels out tiny irregularities, which is what makes water bead and gives that slick, easy-to-wash feel.
- Resists chemicals and UV -- the SiO2 structure stands up to cleaners, traffic film and sunlight better than bare clear coat or wax alone.
About SiO2 percentages on the bottle
The question of whether the SiO2 number actually matters is worth a dedicated read -- see is silica dioxide content important in ceramic coatings? for the short answer. Key points:
- Headline numbers like "70% SiO2" are usually by weight in the concentrate -- not the thickness of the layer on your car.
- A higher number doesn't automatically mean a better coating. The chemistry, solvents, resins and curing system all matter.
- Very high SiO2 content can be harder to apply cleanly without streaks or high spots unless the installer is trained and conditions are controlled.
- Good manufacturers balance SiO2 with other ingredients so the coating is durable, glossy and practical to install -- not just impressive on paper.
SiO2, silicon and silicone -- clearing up the language
- Silicon -- the element (Si) found in sand, microchips and solar panels.
- Silica / SiO2 -- silicon dioxide, the hard mineral material that forms the backbone of most true ceramic coatings.
- Silicones -- flexible silicone-based polymers (often called siloxanes) used to add slickness, gloss and water behaviour.
- Professional coatings may use both together -- SiO2 for structure and durability, silicone components to fine-tune how the coating spreads, self-levels and feels.
Where people get misled by SiO2 marketing
- Short-term "ceramic" sprays often boast an SiO2 percentage but behave more like traditional sealants -- fine as toppers, not substitutes for a full coating.
- Some products lean on SiO2 figures and "nano" buzzwords while saying very little about preparation, curing or aftercare.
- Rebadged or white-label retail products may quote impressive numbers with no test data or installer training behind them.
- If the seller can't explain what the SiO2 is actually doing in plain English, the percentage alone shouldn't be your deciding factor.
What SiO2 cannot do on its own
- Can't hide poor paintwork -- the SiO2 layer is clear and microns thin, so it shows whatever swirls, sanding marks or dull patches sit underneath.
- Can't make paint bulletproof -- even with high SiO2 content, coatings don't stop stone chips or deep scratches from physical impacts.
- Can't replace preparation -- without proper decontamination and polishing, the SiO2 network can't bond properly, and performance suffers.
- Can't remove the need for washing -- SiO2 makes cleaning easier and safer, but the car still picks up dirt and needs regular maintenance.
Best-practice checklist when you see SiO2 on a label
- Ask whether the product is a true, professionally applied ceramic coating or a maintenance topper that happens to contain SiO2.
- Look at the whole system -- preparation, application, curing and aftercare -- not just the quoted SiO2 percentage.
- Favour coatings supplied through trained, accredited installers who can explain how the SiO2 chemistry benefits your car day-to-day.
- Use compatible shampoos and toppers so the SiO2-based layer keeps doing its job for as long as possible.
For the broader "what does a ceramic coating actually protect against" answer, see What are the benefits of a ceramic coating?