What Are Mineral Paints?

…and Why Are Professionals Still Using Them 140 Years Later?

You’ve probably heard the term “mineral paint” tossed around on conservation jobs or listed buildings, but what exactly is it? Why would someone choose these masonry paints over more familiar modern coatings? And what makes Keim – yes, that 140-year-old brand – still the go-to for architects, conservation officers, and specifiers alike?

In this post, we’ll unpack what mineral paints are, how they work, why they’re different from acrylics and emulsions, and where they’re best used. If you’re working with historic brickwork, lime plaster, or new-build render that needs to breathe, read on.

 

 

If you’re thinking it’s just another type of emulsion with a fancier name and a bigger price tag, stop right there. This isn’t marketing fluff. Mineral paint is a different animal entirely.

It all starts with the binder – potassium silicate, also known as liquid glass. Not a gimmick. Not a buzzword. This stuff has been used for centuries. And here’s the magic: it doesn’t just stick to the wall, it becomes part of the wall. Through a chemical process called silicification, it fuses with mineral substrates like brick, stone, or lime render. We’re not talking surface-level here. We’re talking molecular bonding.

 

What’s In It (and What’s Not)

Mineral paints are made with inorganic pigments and natural fillers. No plastics, no resins, no petrochemical junk. That means no VOCs, no smell, and no harm to the air indoors or out. UV rays? Not a problem. These paints don’t fade like synthetic ones because the pigments don’t break down in sunlight. And they don’t burn, either. So yes, they’re fire-resistant too.

Note: there is a clear distinction between fire resistant and fire retardant paints.

Fire resistant paints, such as those made by KEIM, are designed not to melt or drip when exposed to high temperatures. Their composition helps block the spread of fire from one area to another, offering protection by withstanding heat for a set period.

Fire retardant paints, by contrast, work by slowing down the spread of fire. They contain chemicals that either suppress flames or form a protective barrier when exposed to heat.

 

Built for Buildings That Breathe

You know the kind of buildings we’re talking about – solid-walled, pre-1919, built before the cavity wall and cement render came along and ruined the party. These are homes, churches, schools, town halls, farmhouses, chapels, and cottages that were built to move, shift, and breathe with the seasons. They weren’t designed for modern plastic paints or waterproof coatings that seal everything in. Put the wrong paint on these buildings and you’ll do more harm than good.

Think of an old stone church – walls a couple of feet thick, lime mortar between every block, and no damp proof course to speak of. You paint that with a modern masonry paint and you’re asking for trouble. Moisture gets trapped, salts start pushing their way to the surface, and before you know it the paint’s bubbling off in big floppy sheets. But use a mineral paint? Different story. The paint fuses with the surface, breathes with it, and lets water vapour pass straight through.

Same goes for heritage homes – Victorian terraces, Georgian townhouses, even earlier timber-framed buildings with lime render or limewash. These places are alive in a way modern houses aren’t. They expand and contract. They absorb moisture and release it. A good mineral paint works with that, not against it.

You’ll also see mineral paints on historic barns, converted mills, old schools, and traditional pubs – anywhere the building fabric is part of the charm and not something you want to smother under layers of acrylic.

 

 

Here’s where it gets interesting. When you paint a wall with a conventional product – say, an acrylic or emulsion – you’re really just sticking a flexible plastic skin to the surface. That skin might last a few years, but it can peel, flake, or blister over time. Moisture can get stuck behind it. Paint layers build up and get heavy. Eventually, it all has to come off.

Mineral paint works differently. The potassium silicate binder penetrates into the surface and chemically reacts with it. Instead of sitting on top, it becomes part of the wall. That’s silicification.

Because there’s no film, moisture vapour can travel through the paint. The wall breathes, water escapes, and damp issues are less likely to build up. That’s why mineral paints are trusted on older buildings – they won’t trap anything behind them.

And once that bond forms? It’s locked in. You’re looking at decades of protection, not just a few seasons.

 

 

No fluff, no gimmicks – just solid reasons that hold up in the real world.

They Let Your Walls Breathe

Let’s start with the one that matters most, especially if you’ve got older buildings. Lime render, stone, brick – those materials weren’t designed to be sealed in. Put something airtight over them, and moisture gets trapped. Then you’ve got blistering, flaking, and worse – damp building up inside your walls.

Mineral paints are vapour-permeable. That means they let moisture out without letting weather in. The wall stays dry, the paint stays put, and the building can do what it was built to do: breathe.

They Last for Decades – Not Just Years

Most paints look fine for a few years, then you’re back up the ladder scraping and recoating. That gets expensive. Mineral paints, on the other hand, form a chemical bond with the surface. They become part of the wall.

Done right, a good mineral paint system – something like Keim – can last 20 to 30 years without serious touch-ups. That’s not a typo. That’s a proper investment. Less labour, fewer materials, and less hassle over time.

They Don’t Fade in Sunlight

Ever seen a red wall turn pink after a few summers? That’s UV doing what it does – breaking down synthetic pigments. Mineral paints don’t play that game. They use lightfast, inorganic pigments that stay the same colour for decades, even on sun-drenched, south-facing façades.

There’s no yellowing, no chalking, and none of that patchy look you get with cheaper paints after a couple of years.

They’re Fire Safe and Non-Toxic

Modern paints often come with a cocktail of solvents, plastics, and VOCs (volatile organic compounds). Not these. Mineral paints are made with natural materials – things like potassium silicate and mineral pigments. That makes them chemically stable once they’re dry, with zero off-gassing.

They won’t catch fire, and they don’t release smoke or toxins if exposed to heat. That’s why you’ll find them in hospitals, schools, and listed buildings where safety comes first.

They Don’t Feed Mould or Algae

Fungus and algae love organic matter – it’s what they eat. Most modern paints have plenty of it. Mineral paints don’t. There’s nothing in the finish to feed mould, which makes them a smart choice for damp or shaded spots.

If you’ve got a north-facing wall that never dries out, or a garden wall covered in algae every winter, switching to mineral paint can help keep it clean year after year.

They’re the Sustainable Option

There’s a reason architects and conservationists lean toward mineral paints. The ingredients are natural, the lifespan is long, and the emissions are basically zero. You’re not loading the air with solvents. You’re not dumping plastic micro-particles into the environment.

And because you don’t have to repaint every five years, you’re cutting down on waste too. It’s a win across the board – performance, safety, and sustainability.

 

 

Mineral paints aren’t just for cathedrals and castles – though they’re perfect for those too. These paints are made to bond with mineral surfaces like lime render, brick, stone, and concrete. They allow walls to breathe, which means they don’t trap moisture inside. And when you look at where that matters most, the list is longer than you’d expect.

Historic Buildings That Need to Breathe

Old stone buildings and lime-plastered walls need help, not harm. Trapping moisture inside them is like putting a plastic bag over your head – not ideal. Mineral paints allow vapour to escape, helping preserve the original fabric of the building. That’s why they’re trusted on stately homes, chapels, cloisters, and even medieval townhouses still in use today.

Conservation and Listed Properties

When you’re working on a listed building, you can’t just slap on any paint. Conservation officers expect materials that won’t damage the structure – and breathability is key. Mineral paints are often approved for use in these sensitive settings, helping contractors avoid costly compliance issues or denied approvals. Think of Georgian terraces, Victorian schools, or Edwardian libraries being carefully brought back to life.

Public and Institutional Buildings

Hospitals, schools, council buildings, even galleries and transport hubs – anywhere where safety, hygiene, and long service life are important. Mineral paints are non-combustible, low in VOCs, and won’t peel or flake. They’re often specified in high-traffic public areas for that reason.

Modern Renders That Need Vapour-Open Coatings

Not all mineral paint jobs are old-school. On modern builds with silicone or polymer-modified render systems, breathability still matters. Mineral paints offer a finish that resists dirt and algae but still allows the wall to do what it was designed to do – breathe. That makes them ideal for energy-efficient housing, new extensions, and passive house designs.

Concrete, Masonry, and Fair-Faced Finishes

For exposed concrete and bare masonry, especially on car parks, stairwells, and social housing blocks, mineral paints are valued for their durability and bond. They don’t form a skin that might trap water behind them, which is especially helpful on solid walls with no cavity.

Coastal Buildings Facing the Elements

This is where it gets really interesting. Coastal properties face more than just wind and rain – they deal with salt spray, humidity, and constant weathering. Mineral paints like Keim Royalan are built for this exact challenge. They’re used on everything from seaside hotels and spas to holiday rentals, beachside cafés, and boutique Airbnbs. You’ll even find them on second homes, clifftop retreats, and retirement properties with sea views. It doesn’t stop there: coastguard stations, RNLI lifeboat buildings, signal houses, and even lighthouses have been protected using mineral coatings designed to handle the harshest maritime conditions.

Interior Use in Moisture-Prone Areas

Inside, mineral paints shine in damp, poorly ventilated spaces. They’re often used on lime plasters in heritage interiors, but also in modern settings where moisture is a problem. Think church ceilings, vaulted cellars, museums, historic theatres, and even domestic bathrooms in older stone homes. Because they don’t trap moisture, they help control condensation and mould – without relying on plastic-like films.

 

 

Keim invented the modern mineral paint in the 1870s. Their products have been used on the White House, Buckingham Palace, and thousands of heritage buildings across Europe. This is the brand that professionals call on when failure is not an option.

Keim systems aren’t just one-size-fits-all – they’re formulated for different conditions.

Keim Soldalit

A hybrid silicate paint that can go over both mineral and previously painted surfaces. Ideal when you want mineral performance without stripping everything back to bare substrate.

Keim Royalan

Designed for extreme climates – salt-laden air, high UV exposure, temperature swings. Used on everything from lighthouses to Middle Eastern builds.

Keim Innostar / Ecosil-ME

Interior-grade mineral paints with excellent coverage and scrub resistance. They’re clean, bright, and ideal for spaces where people spend a lot of time.

Every Keim product is part of a tested system, with primers, fillers, and finishes designed to work together.

 

 

This ain’t rocket science, but there’s a right way to do it.

Step One: Know What You’re Painting

Mineral paints, like those from Keim, don’t play well with just anything. These are breathable, high-performance coatings made to bond with mineral surfaces – brick, stone, lime render, lime plaster, or bare concrete. That’s the playground.

Now, if someone slapped PVA, silicone waterproofer, or an acrylic sealer on the surface back in 1994, you’re out of luck unless you remove it. The paint simply won’t bond. You’re not painting over something – this paint becomes part of the surface. That’s the beauty and the trick of it.

If the surface has already been painted, that doesn’t mean game over. But you’ll need to run a test patch. Some mineral paints like Keim Soldalit are more forgiving and can go over existing coatings – but only if that paint is sound and solid. No flaking, no peeling. If it’s coming off under your fingernail, it’s not ready.

Step Two: Prime Like You Mean It

This is the bit folks love to skip – and then regret later. Most mineral paint systems use a primer, like Keim Fixativ, to get things started. This isn’t a filler or a stain blocker. It’s a stabiliser.

Fixativ works like a handshake between your surface and the paint. It evens out suction (so your first coat doesn’t vanish into thirsty patches), locks down any chalky bits, and gives your topcoat something reliable to grip.

It goes on diluted – check the data sheet for ratios – and it’s usually brushed on. Once dry, you’re good to go.

Step Three: Apply with Confidence

You’re not reinventing the wheel here. Two coats, brush or roller. No gimmicks, no sprayers, no backflips. Just good paint and even application.

The first coat might look a bit patchy. That’s fine. The second coat brings everything together. Drying times are generous – touch-dry in a couple of hours, and you can usually get the second coat on the same day if weather allows.

Now, conditions matter. You want a clean, dry, dust-free surface. No frost, no rain, and certainly not direct blazing sun on a hot day. Think cool, calm, and consistent. And yes, read the data sheet. Every product has its own rules, and they’re there for a reason.

 

Want your paint to look good and last decades? Don’t overthink it – but don’t wing it either. Follow the system, and you’ll get the results mineral paints are known for. Still not sure? The tech team can talk you through it before you open a tin.

 

 

“It’s just for old buildings.”
Not true. Mineral paints are widely used on modern renders, new-build brickwork, and commercial facades.

“They’re hard to use.”
They follow a clear system. As long as you’ve got the right substrate, they’re no more complex than standard coatings.

“There aren’t many colours.”
Keim offers hundreds of shades, including RAL, NCS, and bespoke colours.

“They can’t go over old paint.”
Keim Soldalit can, as long as the surface is sound and breathable. Always check first.

 

 

Mineral paints are brilliant, but only if you use them where they’re supposed to go. These paints bond by way of a chemical reaction with mineral-based surfaces. That’s their whole deal. So, if you’re thinking about slapping them onto wood, metal, plastic, or any sealed surface, stop right there. You’re setting yourself up for disappointment.

Wood flexes, plastic resists, metal corrodes, and sealers – well, they do exactly what they’re supposed to: block out anything trying to stick. Mineral paint needs to soak in and react with the surface. If that can’t happen, the bond fails and the paint will crack, flake, or peel.

Same goes for glossy emulsions or those water-repellent silicone-treated renders. Think of them like a raincoat. Water rolls right off – and so will your paint. If the surface has any kind of barrier, the mineral paint won’t be able to do its job.

Not sure what’s on your wall? No shame in that. Here’s the smart move: use a Keim colour sample or a consumption-rate sample. The colour sample helps you see the real thing before you commit – none of that guessing from a screen. And the consumption-rate sample? That gives you a good idea of how much paint the surface will drink up. Some walls are thirsty. Others, not so much.

And if you’re still scratching your head, try a small test area first. That’s like taking the car for a test drive before buying. It tells you everything you need to know – how it looks, how it sticks, and how it behaves in real life. Read our blog post for more information on the benefits of masonry paints.

 

Need Help with Specification?

Mineral paints such as Keim systems are high-performance, professional coatings. That means getting the right product for the right job is essential.

If you’re planning a large project – especially on heritage buildings or painting exposed masonry – technical advice is available. Substrate testing, site visits, and specification support help make sure everything works first time.

Contact the team to arrange a consultation or full project spec. Got a question? Leave it below for our team to come back to you.