Title: Fondamenta Zaguri
Author: Umberto Sartory
Company: Nuovo Rinascimento

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Visual introduction to the problem and its causes

The real, immediate peril for the city of Venice does not come from sinking, nor it comes from the high tides. The real lethal danger for the town actually is the smog emitted from the intensive traffic of great ships, burning low-cost fuel, with no limitations on sulphuric and nitrogen pollutants released in the atmosphere.

The city’s climate is particularly dump, and these emissions become a bath of sulphuric and nitric acid , that literally crumbles the stones, at the impressive rhythm that is documented in this site

Ships like the ones you see, more times a day walk across the historical centre along the Canale della Giudecca, and berth at its quays for days, with the engines on to sustain the need of energy of such floating towns

The effect of sulphuric acid wastes the marbles, as you can see in these images, while the nitric acid crumbles the brick in a deep hydrolysis. Detailed and wide evidences of these phenomena are documented on the site savevenice.net.

This kind of “Regatta” is killing the city of the “Historical Regata”.

Dramatic walk across the “sestiere” of *

The movies of the "dramatic walks" are not dubbed, as the commentary consists of the name of each locality and the name of the observed phenomena (“hydrolysis of the silicates" and/or "sulphation of the carbonates”; few times: “chemical aggression on sandstones”).

Fondamenta Zaguri

Part A

Here is fondamenta Zaguri, in the sestiere of Saint Mark.
Bricks are mainly composed by silicates, which are sensible to the nitric anhydrides.
When exposed to this pollutant they suffer the phenomenon called hydrolysis, which makes them crumble.
Diesel engines, mainly those of the great ships, burn very heavy oil known as bunker fuel, releasing these chemical agents in the atmosphere by tons.
You can see that this crumbling cannot be ascribed to the age, cause it is happening in real time, under the caress of my fingers.
We’ll see further on, how the breaking down in pieces happens not only to old bricks like these ones, but also to the new ones, used to hide the damage on the walls.

Part B

By the way, please note that the crumbling is not an effect from the sea salinity. This salt, on the contrary, protect the clay of the bricks, with the electrolytic power of its potassium nitrate.
As on the marbles around town the cracks are being hidden through ridiculous filling with putty, the brick walls are patched with new stones, which aesthetical effect is ugly. But these new brick are as well suffering by hydrolysis, being the problem not a question of age but of chemical reaction.
Here is how the new stones act, under the effect of the hydrolysis generated by nitric anhydrides.
This is not a question of centuries, nor years: this is a question of mounths.

Part C
Below we can see the effect of sulphur on the calcium carbonates.
Here the Istria stone, our best marble, goes in dust under my hands.
As I told, it is not a question of centuries or years: under my caresses the wall crumbles down in dust, the marble crumbles, the Istrian stone crumbles.
This is no more Istrian stone, this is gypsum, and buildings cannot carry their weight on chalk.

Real time distruction at Holy Spirit Church on the Zattere

The church of the Holy Spirit on the Zattere, In Venice.
Sulphation is totally erasing any kind of decoration on this building.
I want you to participate to the disappearing of this decoration, which adorns the façade of this church since more than 4 hundreds years.
Under my fingers the flakes of stone will crumble on the floor.
In a very short time, let’s say in a few months, nothing will remain of this artwork.
I do not want to go any further, but you can clearly see how short is the time that we will not be anymore able to recognize this object

Crumbling of the stylobate of San Trovaso church

Church of Saint Trovaso, in the “sestiere” of Dorsoduro.
The stylobate of this church, made in red Stone of Verona, is by now completely crumbled by the nitric and sulphuric anhydrides emitted by the ships.
I have no words to describe the state of these stones, but an action can be clearer of a thousand words.
The nitric and sulphuric desegregation is totally destroying this monument.
The stone crumble in pieces of a weight of ounces.
We must remember that on this stylobate the weight of the façade of the church stands.

Loss of the pierced embossing in the capitals of the Basilica of San Marco

On the opposite side of the Basilica the effects of corrosion are even more evident.
As can be seen, the pierced decoration that was tied to the body of the capital through thin marble peduncles, is completely detaching itself, or better it is already largely detached and disappeared.

Corrosion of the acanthus leaves in other capitals of the Basilica di San Marco

The coal black coat of these capitals relatively protected them from the aggression of sulphur, which “eats” first the carbon on the surface. But by now, as can be seen, the sulphur holed this protective coat in more than one spot, and it is producing the terrible chalky pustules that are visible in these images.

Status of Verona's marble in the base of the Basilica of San Marco

Besides the loss of the decorations, one has to point out dangers in the same static of the buildings. In particular, let’s see in what a condition the sulphuric aggression is reducing this base slab made of Red Verona marble. One can easily see how the calcite veins across the stone have been completely eroded, so that now this is no more a solid and cohering stone, but kind of a 3d puzzle joint, similar to a Berrocal’s sculpture. This kind of structure would be in great danger even with small earthquakes, being subdivided in the components of its conglomerate by the dissolution of its veins of crystalline calcium carbonate, or calcite, that we can see here as empty lines in the body of the stone.
On the surface are already evident the signs of the detaching of parts, and the surface itself, that was cleanly polished till a few years ago, now shows as scabrous and gravely.

Status of Verona's marble in the base of the palazzo Bembo in Rialto

Bembo Palace in Rialto: the base.
As can be seen these are not phenomena of centuries old corrosion: a light caress to the stone is sufficient for the stone to crumble. This is red marble from Verona, a very delicate stone. It suffers both, the sulphation of the carbonates and the hydrolysis of the silicates, being a fossilized conglomerate of clay and small organic bodies, i.e. shells.
I am not going to detach these nodules, but a soft pressure of my finger would be sufficient to do that.

Sectioning of the little column in fondamenta Fontegheto in San Marco

We are facing one of the most glaring examples of the corrosion of calcite veins.
This little column was entire, until few days ago.
But a flat and long vein of calcite, crossing it from side to side, sectioned it.
On the 30^th of July of this year 2003 the column separated in two parts, and in its interior we cannot find any trace of the calcite that was joining the two parts.
We can see a similar phenomenon also on the Zattere, where the objects still look entire only because their bases are immersed in concrete.