Rinzaffo MGN is not an ordinary lime plaster. It performs several distinct and complementary roles that make it unique among heritage plasters.

At its core, Rinzaffo MGN is Roman pozzolanic lime mortar that acts as a moisture and salt management system — one that works naturally with the wall rather than against it. It performs three essential functions that together explain its exceptional qualities and longevity:

1. LIQUID WATER BARRIER: Rinzaffo blocks liquid water, protecting the masonry from wind driven rain, rising damp and surface wetting, yet remains fully vapour open.
2. HUMIDITY CONTROL: by regulating evaporation from the wall, Rinzaffo keeps both the wall and the indoor environment dry, stable and balanced.
3. SALT BARRIER: it prevents salt migration and crystallisation, keeping salts harmless within the wall instead of allowing them to damage the surface.

These three functions — water barrier, humidity control and salt protection — are what make Rinzaffo MGN truly special. Each is vital on its own, but together they create a self-regulating system that keeps walls dry, breathable and durable for decades.

The following chapters explore how each of these mechanisms work in detail.

By adding volcanic sands and ashes (natural pozzolans) to lime, the Romans created mortars that could harden even under water — the first true hydraulic limes in history. These plasters resisted moisture without losing their ability to breathe, a property modern cements lack. Rinzaffo MGN continues this Roman tradition: a pozzolanic lime plaster that resists water in all its liquid forms — wind-driven rain, rising damp and surface wetting — while remaining completely vapour open.

Ordinary lime plasters are macroporous, containing relatively large pores. Because of this, both liquid water and vapour can pass through them. When the pores are large enough, liquid water moves freely by capillary action — the same way a sponge draws up water. This is why traditional air-lime plasters can absorb water even while they breathe.

When volcanic materials are added to lime, the pozzolanic reaction transforms the internal pore structure. The pores become much smaller, more regular and closely interconnected, forming a super-fine pore network that allows only vapour molecules to pass. At this very small scale, the surface tension of liquid water that acts like an elastic skin prevents liquid water clusters to squeeze through the ultrafine pores, while water vapour can diffuse freely.

In practical terms, Rinzaffo MGN behaves like a Gore-Tex jacket for walls — waterproof on the outside, yet breathable to allow the moisture from the fabric to escape.

Under the microscope, Rinzaffo MGN reveals this refined nanoporous network — a structure that blocks liquid water but lets vapour move through easily. The result is a plaster that protects the wall from external moisture while still allowing it to breathe and dry naturally.

The graph above demonstrates this concept. Ordinary air-lime mortars contain large pores (right peak) that allow both vapour and liquid water to move through. Pozzolanic limes like Rinzaffo MGN shift the pore structure toward much finer, uniform pores (left peak), where liquid water cannot enter but vapour can still diffuse freely.

Once liquid water is kept out, the next challenge is managing the vapour flow that is present inside the wall and the surrounding environment — and this is where Rinzaffo’s humidity control ability comes into play.

Every masonry wall, even a dry one, constantly exchanges water vapour with its surroundings. It absorbs moisture when humidity is high and releases it when conditions are dry. This slow “breathing” process is what keeps traditional walls in equilibrium.

When this balance is disturbed — for instance, by impermeable coatings such as cement render, plastic membranes or bitumen layers — moisture becomes trapped. The wall can no longer release its internal humidity, leading to condensation, moisture accumulation and long-term decay.

Rinzaffo MGN restores this natural balance by acting as a true humidity regulator. It allows the wall to breathe freely but at a controlled, moderated rate, maintaining steady humidity both within the masonry and inside the building.

When Rinzaffo MGN is applied, this behaviour changes entirely. The wall no longer breathes in a chaotic, two-way rhythm but instead becomes a controlled one-way flow system that releases moisture steadily and safely.

Rinzaffo’s fine nanoporous structure acts as a precise moisture regulator. After rainfall or during periods of high humidity, when the wall becomes temporarily overloaded with moisture, Rinzaffo’s countless interconnected pores allow vapour to diffuse through the plaster at a balanced, controlled rate, evening out large, uncontrolled bursts of humidity.

As a result, the indoor environment becomes stable and comfortable and the overall moisture level in the room decreases, greatly reducing the risk of condensation and mould growth.

Thus, Rinzaffo keeps the building’s internal climate drier, calmer and more predictable. It still allows the wall to breathe naturally — but in a measured, moderated way ensuring that both the wall and the indoor air stay in balance, even under shifting outdoor conditions.

Rinzaffo’s selective permeability — blocking liquid water while allowing vapour to escape — also transforms how the wall itself behaves. In a wall without Rinzaffo, moisture moves in both directions: evaporating in dry weather and reabsorbing in wet conditions. With Rinzaffo applied, this process becomes almost entirely a one-way flow — the wall constantly drying. Here’s why:

• When the external environment becomes humid, Rinzaffo’s ultra-fine pores block liquid water from entering. Inside the wall pores, the water vapour pressure of the damp masonry remains near saturation and therefore higher than that of the external air, resulting in a slow, steady outward drying flow, from higher to lower pressure. The physical process driving moisture through small pores is diffusion.
• When the external environment turns drier, outside humidity drops and the pressure difference across the plaster increases. Rinzaffo then “pumps” vapour out faster, accelerating the outward drying flow.

Over time, this becomes a continuous self-regulating drying cycle. The wall steadily loses more moisture than it gains, gradually reaching a new stable equilibrium, staying dry and breathable.

Rinzaffo MGN therefore acts as a passive, one-way “wall-drying” system, continuously "pumping out" moisture from the wall — drying out the wall fabric, while also regulating the indoor environment.

Condensation is one of the most common and hidden dampness sources in old buildings. While we often think of condensation as forming on visible surfaces — misted windows or surface moisture — a more destructive form happens inside solid masonry. When vapour moving through a wall cools below a critical temperature — the dew point or condensation temperature — moisture then condenses inside the wall fabric, often unnoticed, gradually soaking the masonry. This is known as interstitial condensation occurring under the surface.

This problem is made worse by impermeable materials such as plastic membranes, vapour control foils, cement renders or bituminous tanking. These non-breathable systems block vapour movement entirely, causing moisture entrapment behind the surface. Over time this can lead to (hidden) persistent dampness problems and mould. 

It is important to understand that interstitial condensation cannot be fully prevented. In changing weather conditions — for instance, when a warm day is followed by a cold night — small amounts of condensation can form inside any wall. What matters is how quickly that moisture can disperse.

In non-breathable systems, condensation becomes trapped in the wall and accumulates, turning a short-term event into a long-term problem.

Rinzaffo MGN solves this by allowing interstitial condensation to evaporate naturally, without becoming locked inside the structure. When humidity falls, the dew point moves outward again, meaning inner sections of the wall remain safe and unaffected by condensation. Even more importantly, this process is self-regulating: the damper the wall becomes, the greater the vapour-pressure difference between the wall core and the surrounding air, and the faster moisture is driven outward as vapour. In other words, as the wall gets wetter, Rinzaffo automatically accelerates the drying process, helping the structure to return to equilibrium instead of staying saturated.

By maintaining this active balance, Rinzaffo MGN constantly and dynamically manages the dew point, keeping it near the outer face of the wall and away from internal surfaces. Any brief condensation that occurs is short-lived and quickly re-evaporated.

In this way, Rinzaffo maintains a steady internal climate free of condensation, acting as a true vapour control layer (VCL). Unlike modern “vapour control” membranes, which do not regulate moisture but block it completely, Rinzaffo MGN respects the fundamental principle of historic buildings: walls must breathe to stay dry.

But one last challenge and threat still remains — salts.

In most old walls, the main cause of plaster failure is not dampness itself but the salts that travel with it. Wherever water moves through masonry, it dissolves soluble salts such as sulphates, nitrates and chlorides, carrying them toward the surface. As the moisture evaporates, these salts crystallise within the pores of the wall or beneath the plaster.

Over time, this repeated cycle of migration and crystallisation exerts enormous pressure inside the pore structure, bursting surfaces, detaching plasters and crumbling stone or brick — the familiar pattern of decay seen on many damp walls.

Rinzaffo MGN breaks this cycle completely. It doesn’t absorb salts or neutralise them; instead, it changes the environment in which they exist, keeping them stable, rendering them harmless inside the wall.

The same ultra-fine, continuous pore structure that blocks liquid water also acts as a barrier, a physical filter against salts. When damp masonry pushes moisture toward the surface, the first layer to resist that movement is Rinzaffo MGN. Its nanoporous matrix acts like a microscopic filter: water vapour can escape, but the much larger salt ions are trapped and left behind within the wall.

As a result, salts never reach the outer surface, so crumbling, blistering and discolouration stop. The plaster remains clean and intact, while the masonry behind gradually dries.

Importantly, Rinzaffo MGN does not absorb salts. Because salts cannot physically penetrate its fine pore network, they do not accumulate inside the plaster. This means Rinzaffo does not sacrifice itself over time, unlike large-pore “sacrificial” plasters, which are designed to soak up salts and eventually crumble when filled, needing replacement.

In this way, Rinzaffo MGN offers exceptional longevity — performing reliably for decades even in heavy water and salt exposure, without losing adhesion or surface integrity.

Rinzaffo MGN is designed to be softer and more sacrificial than the historic fabric it protects. When it eventually reaches the end of its long service life — often after several decades of exposure to damp and salts — it doesn’t damage the underlying masonry.

Instead, it fails gracefully, eroding slowly at the surface while maintaining its bond and leaving the original brick or stone intact. This gentle, predictable ageing process ensures that the historic substrate always remains safe, even in severe salt or moisture conditions.

This behaviour can be clearly seen in the "Magazzini del Sale" in Venice (The Old Salt Storage of Venice), where Rinzaffo MGN continues to protect soft 16^th century handmade bricks. In areas of extreme exposure, the plaster shows controlled surface wear — proof of its sacrificial function and long-term compatibility with fragile historic masonry.

Rinzaffo MGN is chemically stable and entirely salt-free. It resists all salts — sulphates, chlorides and nitrates — and does not react with them. Instead, it changes how salts behave within the wall.

When dampness carries dissolved salts toward the surface, the nanoporous structure of Rinzaffo MGN slows this movement down. Because the rate of evaporation is moderated and balanced, the salts below the surface never experience the rapid drying that triggers crystallisation. Instead, they remain in a non-crystalline, soft, gel-like state, suspended within the moisture film of the wall.

This is a smart, passive form of salt management: by controlling their environment, the salts are kept in a harmless state, creating no pressure and no damage to either the masonry or the plaster.

Over time, as the wall continues to breathe and gradually loses moisture, the salts stay inert and non-crystalline. This prevents the destructive cycles of crystallisation and re-dissolution that typically destroy ordinary lime and cement plasters.

Thanks to this chemical stability, Rinzaffo MGN maintains its integrity and bond for decades in salt-laden, marine or groundwater-affected environments, offering enduring protection without hardening, cracking or detaching.

Rinzaffo MGN is more than a plaster — it’s a complete moisture and salt management system based on ancient Roman technology, refined for modern conservation.

By combining three vital functions — a liquid water barrier, humidity control and a natural salt barrier — it protects historic walls in the way they were meant to function: dry, breathable and self-regulating.

Its nanoporous structure keeps out liquid water while allowing vapour to escape; it regulates humidity to prevent condensation and mould; and it stabilises salts so they can no longer damage the masonry. Even after decades of service, it fails gently and sacrificially, preserving the original brick or stone beneath.

Proven on thousands of heritage buildings across Venice and beyond, Rinzaffo MGN stands as a modern continuation of the Roman pozzolanic lime tradition — a breathable, durable, and reversible protection system for the long-term preservation of historic masonry.