RAKU for Marble and Limestone: Ultimate Stain and Acid Resistance in Zürich

A First in Zürich

Yesterday at The Hochwert Library, seasoned architects and interior designers gathered for something unprecedented. Together with our partners HÄGNI and NAKU, we presented RAKU, a treatment that fundamentally changes what marble and limestone can be. For the first time, the profession witnessed a polished marble surface resist acids, stains, and heat without a trace of damage.

Setting the Stage

Before the test began, we addressed the room. Everyone present knew the rules of marble: a single drop of lemon or wine is enough to leave its mark forever. We explained that RAKU was designed to challenge those rules, to prevent a reaction that every architect has seen countless times in kitchens, bars, and bathrooms. The audience listened with curiosity and enthusiasm, ready to see something new.

The Demonstration

Then the test began. A pristine slab of Greystone marble, prepared by NAKU, was divided into two halves. One side untreated, the other treated with RAKU. Lemon juice was squeezed directly onto the polished stone, followed by champagne, and finally a concentrated acid known to etch marble within seconds.

On the untreated side, the reaction was immediate and dramatic. Within seconds, the acid completely ruined the surface, leaving the familiar dulling and etching that every professional knows. For many in the room, this was the first time they had seen just how strong and fast-acting this acid could be. Attendees leaned in, visibly shocked, but also fascinated.

On the RAKU-treated side, however, the marble remained flawless. The polish stayed intact, untouched by the acid. Conversations sparked instantly. People examined the stone under the light, touched the surface, and exchanged astonished glances. The room buzzed with excitement—what they were seeing was unmistakably revolutionary.

From Demonstration to Discussion

After the test, glasses were raised and the discussion took off. Architects and designers who had entered curious were now openly amazed, sharing ideas about new possibilities. Marble for kitchens without hesitation. Limestone for hotel vanities. Bars and restaurants clad in stone that could finally withstand daily use. The atmosphere was both celebratory and analytical — a mixture of professional admiration and genuine excitement.

What Makes RAKU Different

The secret to RAKU lies in what it does not do as much as what it does. It does not alter the colour, sheen, or feel of the stone. It does not create a plastic-like film on the surface. Instead, it establishes a permanent, invisible barrier that prevents acid from ever reaching the marble in the first place.

This is not a temporary measure. Applied once, by two trained technicians, RAKU is designed as a lifetime treatment. It is a precise and delicate process, exclusive to HÄGNI, ensuring the application meets the highest standard. For architects, this means specifying marble without disclaimers or compromises.