Technical reference · for specifiers
Marble, calcite, and the limits of a surface coating.
The deep version, for stonemasons, builders and specifiers who want the chemistry with the honest bounds attached. We make the one and only next-generation sol-gel surface coating in Australia. This page explains precisely why polished marble is the substrate where even that runs out of surface to work with.
The substrate, in numbers
What makes polished marble the hard case.
Three properties decide how well any surface coating anchors: mineralogy, porosity, and surface finish. Polished marble sits at the difficult end of all three at once. That combination, not our chemistry, is the constraint.
Near-pure calcite (CaCO₃). No reactive surface silanols for a sol-gel to graft to, unlike quartz, glass or cement.
Dense metamorphic stone. Little open pore network for a water-based sol to wick into and key against.
A factory polish closes the surface further, removing the residual micro-porosity a coating would otherwise anchor into.
Dissolves in acid (CaCO₃ + 2H⁺ gives Ca²⁺, water and CO₂). Etching is material loss, not a stain.
The anchoring chemistry
Marble denies the anchors that make carbonate hold.
Our coating is the one and only next-generation sol-gel surface coating in Australia: a water-based inorganic network roughly 90 to 100 nanometres thin, colourless and breathable, that anchors into the mineral and pore structure of stone by up to four stacked routes. The full two-family mechanism, siliceous versus carbonate, is set out in stone and sealer chemistry. Polished marble is the one substrate where that mechanism runs out of surface to grip, and here is precisely why.
The pore interlock that carries carbonate is the first thing marble denies
On porous carbonate the water-based sol wicks into the open pore network and condenses in place, keyed into pore mouths and grain contacts, and more porosity means a better key. That is exactly why travertine and limestone anchor so well. Dense, polished marble has almost no open porosity, and the mirror polish closes what little remains, so the anchor that does the work on carbonate is the one that is missing here.
Near-pure calcite offers no silanols to graft to
On siliceous stone, concrete and the cement fraction of liquid or reconstituted limestone, the coating grafts covalent Si-O-Si into the surface's own silanols, the strongest anchor of all. Near-pure calcite supplies none of that silica. Genuine Si-O-Si still forms within the coating, as a self-condensed cohesive network, but on a smooth polish with nothing to interlock into and no silica to bond to, that film has little to hold it in place. It is the difference between marble and, say, granite.
Hydrogen bonding, a contributor, never the anchor
The coating hydrogen-bonds to the adsorbed surface-water film and to under-coordinated calcium and step-defect hydroxyls on the carbonate. This is real, and it is why alkoxysilanes still raise the water contact angle on limestone even where calcite bonding is weak. It is a supporting effect, not a load-bearing grip, and on a dense polish it is most of what remains.
A regime note worth making. The stone-conservation literature that says alkoxysilanes bond poorly to marble is testing deep consolidation, re-cementing loose grains through 25 millimetres to carry structural load. That is a far harder ask than a 90 to 100 nanometre surface repellent, and the same studies still measure a raised contact angle and reduced absorption on limestone. The finding is real, but it is the wrong regime to import onto a thin surface coating. On porous carbonate we win on both the anchor and the fit. Dense polished marble is the genuine exception.
Us versus the legacy options
On polished marble, every class hits the same wall.
This is the honest part specifiers appreciate: on a dense, acid-sensitive polish, no class of product solves the core problem, because the core problem is the material. The full film-versus-pore-versus-bonded comparison is in the three ways to seal a surface. Here is only how each one lands on marble.
Our sol-gel surface coating
- On honed, tumbled or outdoor marble, where it can anchor, it is colourless, breathable, genuinely oil-repellent and PFAS-free, and it will not yellow in the sun.
- On a mirror polish it has little pore structure and no calcite silanols to grip, and it cannot stop acid etching, so we tell you plainly rather than sell you a promise.
The legacy options
- A penetrating impregnator relies on absorption, and a polished marble barely absorbs, so it does little.
- A topical film can act as a sacrificial acid barrier, but it alters the look, wears, yellows, traps moisture on stone that needs to breathe, and must be stripped to redo.
None of them stop acid etching either, because the acid reacts at the exposed surface it touches. That limit belongs to the stone, not to any sealer.
The resistance edge, with the bounds
What the coating resists, and where it stops.
On marble open enough to anchor, honed, tumbled or outdoor, the reason to choose our chemistry over an impregnator is the same real-world-resistance edge it brings to every stone. All four resistances, cleaning, chemical, UV and oil, with the honest bound on each, are set out in surface resistance in the real world. On marble, one bound dominates the rest.
The edge, on open marble
Survives the cleaning, will not yellow, lifts oil
Anchored at the surface, the coating holds up to the mopping that wears ordinary sealers off and tops up without stripping, stays more stable to routine alkaline cleaners than an organic film, will not yellow or chalk in the Perth sun, and lowers surface energy so oil and wine lift instead of soaking in, PFAS-free by design. Every one of those is more resistant, not immune, and the full detail is in the pillar above.
The bound that dominates on marble
No protection against acid etching
It offers no protection against acid etching of the carbonate itself. Acidic foods and cleaners will still etch the marble under the coating, because the acid reacts at the exposed surface without needing a pore to soak into. That is the one exclusion that matters most on this stone, and it is the next thing we set out plainly.
The one exclusion that matters most
Etching is material loss, not a coating failure.
Acid etching is the carbonate dissolving at the exposed face: CaCO₃ plus acid gives soluble calcium, water and carbon dioxide. It is a micro-crater of missing stone, correctable only by mechanical re-honing or re-polishing, never by cleaning and never by any penetrating sealer. The acid reacts at the surface it touches, so there is no pore for a sealer to defend. This is why our guarantee, like the physics, covers the coating's repellency function and explicitly does not cover etching, physical wear, weathering, fading, or staining from spills left to sit. How that guarantee sits beside the honest upkeep, and what no seal on any stone can stop, is in living with a sealed surface. Guaranteeing etch-resistance on marble would be the real fine print to worry about.
The disciplined framing across our copy: on siliceous stone, concrete and glass the coating bonds into the surface itself. On porous carbonate it anchors into the mineral and pore structure. On dense, polished, near-pure marble it does neither well, and we do not claim it does. Naming that limit is the trust play, and it is also simply correct.
Go deeper on the science
The shared chemistry lives in the pillars. Follow it down.
Pillar · the mechanism
Stone and sealer chemistry
Siliceous versus carbonate, the two mineral families and the four anchoring routes. The full mechanism marble is the honest exception to.
Read the pillar →Pillar · the classes
The three ways to seal
Film versus pore impregnator versus bonded coating, the full head-to-head on where each protects and how it fails.
Read the pillar →Pillar · living with it
Living with a sealed surface
The two clocks, the reseal that tops up without stripping, and what no seal on any stone can stop.
Read the pillar →Plain English
The marble guide
The same answer without the chemistry: what a coating can and cannot do for polished marble.
Read the guide →Browse
The Sealing Library
Every WA surface by material, graded honestly for how well our coating protects it.
Find your surface →Get a quote
Specifying stone? We'll give you the straight read.
Tell us the stone, the finish and the use. We will tell you honestly whether our coating earns its place, and where it does, we seal it under a 10-year guarantee.