How a quiet revolution in ceramics changed how we make and understand wall tiles
When you fire ceramics, they densify. And when they densify, they shrink.
That has been one of the oldest and most predictable laws of materials science.
As the temperature rises, particles of clay fuse together and gases escape. The object becomes smaller and stronger, a process known as firing shrinkage.
This is why, for decades, wall tiles were always double-fired.
The body was fired first, allowed to shrink and stabilise, and only then was the glaze added and fired again.
If you glazed an unfired body and both layers shrank differently during heating, the tile would warp or crack.
Imagine sewing a perfectly fitted cloth cover onto a sponge cushion, then heating it until the sponge shrinks. The cloth has nowhere to go, so it wrinkles and tears as the base underneath gets smaller.
And yet, in the early 1980s, Italian engineers found a way to fire both the body and the glaze together in one single cycle without any warping or shrinkage.
They called it monoporosa, meaning single porous body.
It became one of the greatest scientific wonders in modern ceramics — the art of sintering without shrinking.
The Birth of an Idea
Before monoporosa, double firing was the only reliable way to produce glossy wall tiles. It gave excellent results but consumed more time, energy, and factory space.
The challenge was not mechanical — it was chemical. The goal was to create a body that could strengthen under heat yet remain dimensionally stable.
Italian engineers formulated new frits and experimented with carbonate-rich compositions. Their work resulted in the development of a ceramic body that resisted shrinkage completely.
The first monoporosa tiles were displayed at the 1982 CERSAIE Exhibition in Bologna.
A year later, Ceramica Faetano in San Marino began industrial production, marking the beginning of a new era for the ceramic industry.
A new chemistry turned the oldest rule of ceramics on its head — firing no longer meant shrinking.
The Secret of Carbonates
The breakthrough came from rethinking what happens inside the clay during firing.
It was realised that by carefully adding calcium carbonate (CaCO₃) and dolomite (CaMg(CO₃)₂) to the body, they could make chemistry work against shrinkage.
Normally, sintering pulls particles closer together as they fuse. But when carbonates decompose under heat, they release carbon dioxide gas and create new crystalline phases. These crystals form a microscopic skeleton that holds the structure open — balancing the forces that cause contraction.
As the temperature rises:
- Around 650–700°C, the carbonates begin to decompose, releasing CO₂.
- The calcium and magnesium left behind react with the clays and silica.
- By 900–1000°C, they form new crystal phases such as wollastonite (CaSiO₃), gehlenite (Ca₂Al₂SiO₇), and anorthite (CaAl₂Si₂O₈).
These crystals grow like fine needles through the ceramic matrix, reinforcing it from within. The gases that escape leave behind gentle porosity — enough to prevent collapse but not enough to weaken the tile.
The result is extraordinary: a body that sinters — but does not shrink.
Turning Fire into Structure
In a normal ceramic, the densification process dominates.
Particles move closer together, pores close, and the body becomes smaller and denser.
In the monoporosa body, however, two opposite reactions occur at the same time:
- Sintering, which tries to make the body smaller.
- Gas evolution and crystal growth, which push back and hold the structure steady.
The two effects cancel each other out. The body matures, vitrifies, and hardens — but remains the same size.
This perfect equilibrium is what made the monoporosa process so revolutionary.
From Invention to Industry
By the mid-1980s, monoporosa had transformed wall-tile production across Europe.
Spain embraced it quickly because of its quartz-rich clays, and within a few years, single-fired glossy tiles had become an international standard.
The benefits were undeniable:
- Lower energy consumption
- Reduced production cost
- Smaller Space
Today, most modern wall tiles trace their lineage back to this innovation.
The monoporosa process did more than make tiles cheaper — it redefined how we think about materials.
It proved that sintering does not always mean shrinking, and that porosity can exist in harmony with strength.
A Lesson in Harmony
At its core, monoporosa is a lesson in harmony. The body and glaze each with their own character come together to survive the fire as one.
Every glossy wall tile that decorates a bathroom or kitchen today carries the legacy of this quiet revolution.
Beneath its smooth surface lies a perfect equilibrium — a body that refused to shrink, a glaze that learned to wait, and an engobe that kept the peace.
Even the simplest objects can hold extraordinary science.
That is the wonder of sintering without shrinking — where chemistry, fire, and precision meet to create something both technical and timeless.