Technical reference · clay & face brick
Sealing brick, from the chemistry up.
The specifier's version. Why an inorganic sol-gel is the right architecture for fired-clay masonry, how it anchors into an aluminosilicate surface, why vapour permeability is the whole argument on brick, and where the honest bounds sit on efflorescence and salt. MineralProtect is the one and only next-generation sol-gel surface coating in Australia, and here is exactly how it behaves on brick.
At a glance
The coating on brick.
Silica-rich, silanol-bearing, porous. Siliceous, not carbonate.
Cross-linked Si-O-Si network, roughly 90 to 100 nm dry.
Bonds into the surface and pore structure. Porosity helps.
Changes surface energy, does not cap the pore mouths.
No wet-look, no darkening, no sheen.
Per-job registration through a Certified Applicator.
The mechanism
Why an inorganic sol-gel suits fired clay.
The shared mechanism is the same on every porous mineral: a water-based sol-gel condenses into a cross-linked Si-O-Si network that cures conformally at the surface itself, colourless and thin enough to change surface energy without laying down a visible film. We cover that architecture in full in the pillar. What follows is only what is specific to brick, and brick happens to be one of the strongest substrates we treat.
Fired clay is a silanol-bearing surface
Brick is an aluminosilicate, chemically far closer to sandstone and concrete than to carbonate stone. Its surface carries reactive silanol groups, so the sol's own silanols condense with them to form genuine covalent Si-O-Si bonds continuous with the substrate on cure. This is real chemical integration, the full-strength version of "bonds into the surface," not the softened wording carbonate stone requires.
Porosity is an advantage here
Face brick has an open pore network. The water-based sol wicks in and condenses in situ into a rigid network keyed into the pore mouths and grain contacts, so covalent bonding and mechanical interlock stack. Higher porosity improves the anchoring, the inverse of dense, polished stone where the absence of pores is the hard case. The layer stays thin enough to lift surface energy without capping the pore mouths, which is the entire vapour argument below.
The decisive property on masonry
Vapour permeability is the whole argument.
A brick wall manages moisture by drying. Water enters as rain, capillary rise or reticulation overspray and leaves as vapour through the face. Break that drying path and you don't stop the water arriving, you only stop it leaving, which relocates the damage.
An organic film former, acrylic, epoxy or polyurethane, caps the pore mouths as a continuous low-permeability membrane. It seals against liquid water and water vapour, which is exactly why the building-conservation trade warns that such coatings should almost never be applied above grade to masonry. The evaporation front retreats beneath the film, soluble salts crystallise there as destructive sub-florescence rather than harmless surface efflorescence, and crystallisation pressure spalls the face. Add thermal-expansion mismatch and a failing film can pull the brick face off with it. A failed film cannot be recoated. It must be stripped.
MineralProtect is architecturally opposite. It changes surface energy without capping the pore mouths, so the vapour path stays open and the wall keeps drying. The honest framing matters here: superiority is against films. Against a quality penetrating impregnator, breathability is broadly parity, because both leave the pores open. We do not claim to breathe better than a good silane. We claim to protect the surface without the film's trapped-moisture failure mode.
Resistance to real-world use
The loads all act at the face.
A wall in service is rained on, pressure washed, baked under UV, scrubbed with alkaline and biocidal cleaners, and fouled with soot and barbecue grime. Every one of those loads acts at the face, which is exactly where our network lives and exactly where a pore impregnator has nothing, because its working repellency is stranded millimetres below the wear zone. The inorganic backbone resists cleaning abrasion, routine alkaline cleaning chemistry, Perth UV and oily marks better than an organic film or a buried silane, and it renews with a top-up rather than a strip.
None of that is immunity. It is not scratch-proof, not abrasion-proof and not permanent; Si-O-Si is stable only at routine cleaning pH and short contact; it is far more UV-resistant than a film, not UV-proof; and oil is an outcome, never a number, since we do not match the fluoropolymer oil repellency that is itself exiting via PFAS regulation. The full breakdown of the four resistances, with the honest bound on each, lives in the pillar.
Go deeper: the four real-world resistances, and where a seal actually has to hold
The head-to-head
Where the protection lives.
The choice on masonry is not brand versus brand. It is architecture. A film former caps the pores and drives the sub-florescence and spalling covered above, and it must be stripped to redo. A pore impregnator buries its repellency millimetres down where cleaning and UV cannot be answered, so the face fails first while the reservoir sits stranded. Our sol-gel puts a dense Si-O-Si network in the top hundred nanometres, covalently bonded to the brick's silanols plus pore interlock, breathable, colourless, and renewed by top-up with no film to strip.
The one brick-specific verdict: on a wall that has to dry, the film former is the classic sealer mistake, because capping the pores is the failure. Everything else about the three-way comparison is the shared story, laid out side by side in the pillar.
Go deeper: film, pore impregnator and bonded coating, compared honestly
Evidence & standards
How durability is measured.
Durability on a coating like this is contact-angle retention across recognised wet-scrub and abrasion cycles, not a hardness rating. The relevant standards, and an honest note on what we do and don't publish for brick.
- Wet-scrub and abrasion. ISO 11998, ASTM D2486 and Taber ASTM D4060 measure retention under cyclic mechanical load.
- Contact angle. ASTM C813 and D8380 cover advancing and post-abrasion static contact angle. Advancing and static figures should not be conflated.
- Independent testing. The chemistry is tested at houses including TÜV Rheinland, SGS, Intertek and REACH. REACH compliant is not the same as, and is a weaker claim than, PFAS-free.
We do not publish a per-substrate ASTM E96 perm figure for brick, and we won't invent one. Vapour permeability here is a design outcome of the architecture, a thin conformal layer that does not cap the pore mouths, not a measured wet-cup delta on your wall. If a specifier needs the number, we commission the test on the actual substrate.
The honest bounds
What it does not do.
It is not damp-proofing. A surface coating cannot stop moisture arriving from behind the wall. Heavy efflorescence or low-level spalling points to a moisture source, leaking reticulation, a bridged damp course, banked garden beds or a genuine coastal salt load, and that has to be addressed at the source. Sealing the face protects it without trapping that moisture, but it does not turn off the tap.
It does not stop efflorescence at the source. Efflorescence is salt transported out of the wall by moisture. No coating prevents it. The defensible position is directional: a breathable surface lets the salt bloom off the front where it cleans away, whereas a film traps it beneath the face. Any salt benefit we state is strictly relative to a film, never an absolute, and on a salt-saturated substrate any water-repellent surface, ours included, can slow drying at the treated face, so we assess salt load and substrate before we commit.
It is not permanent, waterproof or maintenance-free. It is a long-lasting treatment that degrades slowly and predictably and is topped up periodically. It makes cleaning faster and less frequent. It does not remove the need to clean.
Specifier questions
The technical detail.
Is brick a covalent bond or just mechanical keying?
Both, and that is why brick is a strong substrate for us. Fired clay is an aluminosilicate whose surface carries reactive silanols, so the sol condenses genuine covalent Si-O-Si bonds continuous with the substrate on cure. On top of that, the open pore network gives mechanical interlock as the sol condenses in situ. Unlike carbonate stone, where the calcite offers no silanol and the anchor is interlock and hydrogen bonding, brick supplies the silica for a real chemical bond.
How does it compare to a penetrating silane on brick?
A silane is engineered to build repellency millimetres down the pore to slow bulk water ingress, which is the wrong location for surface performance. On a cleaned, sun-hit wall the surface repellency the owner sees dies first: UV cleaves the alkyl tail and cleaning strips the thin top layer, while the buried resin stays detectable but cannot renew the face. We put the network at the surface where the loads act, and it renews with a top-up. On breathability the two are broadly comparable, since both leave the pores open. We do not claim to breathe better than a quality silane.
Why not just use a masonry water repellent or a waterproofing coating?
It depends which one. A vapour-blocking waterproofing coating is precisely the film the conservation literature warns against on masonry: it stops the wall drying and drives sub-florescence and spalling. A breathable water repellent is the right category, and that is what MineralProtect is, with the added surface-energy control that lifts oil and grime rather than water alone.
Does the coating affect the wall's fire or structural behaviour?
It is a roughly 90 to 100 nanometre inorganic surface layer that changes surface energy. It does not consolidate, strengthen or add structural capacity to the brick, and we make no such claim. Its job is surface protection: repellency, easier cleaning and resistance to the weathering and cleaning loads that act at the face.
Can you give a perm rating or an Sd value for our substrate?
Not off the shelf, and we won't quote someone else's number as if it were yours. Vapour permeability here is a mechanism outcome: a thin conformal layer that does not cap the pore mouths, so the vapour path stays open. The perm delta actually worth measuring is against a film former, which collapses toward near-zero. If you need a measured figure on your own brick, we commission an ASTM E96 wet-cup on that substrate rather than hand you an adjective dressed up as data.
Keep reading
Go deeper on the science.
The science · pillar
How surface sealing actually works
The shared mechanism in full: the third class of sealer that bonds a colourless, breathable network at the surface itself.
The science · pillar
The four real-world resistances
Cleaning, chemical, UV and oil: the four loads that decide a seal, each with its honest bound.
The science · pillar
The three ways to seal, compared
Film, pore impregnator and bonded coating, side by side, and why architecture beats brand.
Plain-English version
Sealing clay & face brick
The same argument without the chemistry: the problem, the fix, and the honest limits, for a homeowner.
Same family
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Every common WA surface, graded by how well our coating protects it.
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