Conservation of Building Materials in Venice

Here’s the Word file for the first draft of my paper: conservation-of-building-materials-in-venice.

Wood is composed of three main substances: cellulose, hemicelluloses, and lignin. Here are some images of wood’s cellular structure.

Sound Boxwood. This image shows wood’s cellular structure with no decay. Source: Spirydowicz, et al. Alvar and Butvar: the Use of Polyvinyl Acetal Resins for the Treatment  of the Wooden Artifacts from Gordion, Turkey. JAIC, 2001, 40(1), 43-57.

White rot. Wood that has undergone white rot. White rot is caused by fungus that eats lignin and cellulose. Many cells have been devasted, but some are still intact. Source: forestpathology.cfans.umn.edu 

Wood with white-pocket rot. White pocket rot is caused by fungus that eats the lignin of the wood. Delignification causes a loss in mass of the areas around the cells, causing a loss of structure. Source: forestpathology.cfans.umn.edu 

Wood with brown rot. Brown rot is caused by fungus that eats cellulose. This causes the structure to become incredibly weak, leading to fragmentation of the wood if any stress is placed on it. The fragmentation of the wood is shown in this image, where the cellular structure has been devastated. Source: forestpathology.cfans.umn.edu

Last class, issues on how brickwork is conserved were raised and I wasn’t sure about the answers. Needless to say, I’ve now followed through with more specific research to tell you all how bricks in general are cleaned and protected.

Cleaning Brickwork

Because bricks vary considerably in their composition and manufacturing processes, there is no exact cleaning method. It is very much up to the conservator to decide what processes should be utilized. The fragility of the brick due to wear must be taken into account, as well as the porosity, glazes, dyes, mortar, and washes. (1)

In conservation, water-cleaning is often considered due to its gentle cleaning quality. In the case of brickwork though, water only removes superficial or loosely adhered dirt. (1) High pressure water spraying furthers these results, but will not be used if brickwork is in a very fragile state, as in most of Venice.

A better method for removing salts from bricks involves either a) saturating the bricks and rinsing with chemical cleaning or 2) wet-abrasive cleaning. Upon drying, the efflorescence then can emerge from the pores and be dry-brushed or vacuumed away. (2) In the first method, chemical cleaning is utilized. This involves pre-wetting the surface, cleaning with an alkali-based agent (pH above 7) followed by cleaning with a hydrofluoric acid solution (pH below 7), and thorough rinsing. This chemical cleaning must not be used if the mortar contains lime, as it can dissolve the mortar. (3)

 If bricks are very damaged, the only proper method for repairing the building is to carefully cut out the damaged areas and replace them with new bricks, which should meet current ASTM standards. (4)

Consolidating Brickwork

If highly damaged bricks are not replaced, they can be consolidated with synthetic resins. (5)

1. Ashurst, Nicola. Cleaning Historic Buildings. Vol 1. London: Donhead, 1994, 105 – 106.

2. Ashurst, Nicola. Cleaning Historic Buildings. Vol 2. London: Donhead, 1994, 107.

3. Ashurst, Nicola. Cleaning Historic Buildings. Vol 2. London: Donhead, 1994, 107.

4. Weaver, Martin E. Conserving Buildings: A Manual of Techniques and Materials, Revised Edition New York: John Wiley & Sons, Inc, 1997, 107.

5. Weaver, Martin E. Conserving Buildings: A Manual of Techniques and Materials, Revised Edition New York: John Wiley & Sons, Inc, 1997, 108.

     When conservators attempt to restore and preserve buildings in Venice, they are faced with unique problems: all major building materials used to create Venice are either submerged in water, exposed to constant high levels of humidity, or both. The science behind water’s impact on these building materials is essential to providing Venice with the extra precautions necessary for its preservation.

     At this moment, the focus of this paper is to answer four major questions. Firstly, what are the most prevalent building materials in Venice and what are their chemical and physical compositions? Secondly, what chemical reactions do these materials undergo with water and humidity? Thirdly, how do conservators repair damage done by water while halting or slowing further damage? And lastly, how has this knowledge been applied to conserving Venice?

     My research to date has been centered around answering the first two questions. The building materials on which this paper will most likely focus are wood (specifically oak), stone and marble, and bricks and tiles. Wood is a natural polymeric cellulose material prone to rot and decay in humid environments. Although wood does not directly react with water, high humidity levels cause an increase in biodeterioration due to bacteria, fungi, molds, and plants. (1) Stone and marble, both different forms of calcium carbonate (CaCO3), wear away in the presence of water due to the reaction between carbonate stone, CaCO3, water, H20, and the carbon dioxide, CO2, always present in rain water:

CaCO3 + H20 + CO2 → Ca2+ + 2HCO3-,

where the calcium ions, Ca2+, and bicarbonate ions, HCO3-, dissolve in the water and are washed away. (2) More research needs to be done on the makeup and chemical properties of brick and tile. Bricks and tiles are created from clay, so it would be ideal if information could be found on Venetian clay, bricks, and tiles specifically.

     The direction I plan to take the paper will depend on current conservation treatment in Venice. I have not even begun research in the area of conservation, but I plan on concluding my paper with an evaluation of conservation work in Venice: has enough been done to restore and conserve buildings from water damage? I will try to gather economic figures dealing with how much money is allotted for Venice each year from Italy, UNESCO, etc. and compare this with the costs of restoration and conservation for Venetian buildings and the need for further conservation.

     In conclusion, my research will look at the science behind water’s impact on these building materials in order to show how the science is essential for the preservation of Venice. A secondary goal is to raise awareness for the preservation of buildings in Venice by analyzing the recent conservation work with the current need for conservation. While research has been successful in identifying the most common building materials in Venice and their response to water exposure and high levels of humidity, more research is necessary in the conservation treatments utilized in Venice. This will allow for an analysis of the overall success of conservation in Venice and to see if enough is really being done to protect Venice.

1. M. E. Weaver, Conserving Buildings: Guide to Techniques and Materials, Revised Edition (New York: John Wiley & Sons, Inc, 1997), 18-36.

2. K. L. Gauri and J. K. Bandyopadhyay, Carbonate Stone: Chemical Behavior, Durability, and Conservation (New York: John Wiley & Sons, Inc, 1999), 74.

Bibliography of Sources

Archaeological Wood: Properties, Chemistry, and Preservation. Washington, D.C.: American Chemical Society, 1989.

Brown, Patricia F. Art and Life in Renaissance Venice. New York: Prentice Hall, Inc, 1997.

Cariati, F., Rampazzi, L., Toniolo, L. and A. Pozzi. “Calcium Oxalate Films on Stone Surfaces: Experimental Assessment of the Chemical Formation”, Studies in Conservation, 2000.

Feilden, Bernard M. Conservation of Historic Buildings, 3^rd ed. Oxford: Architectural Press, 2003.

Fletcher, Caroline and Jane Da Mosto. The Science of Saving Venice. Turin: Umberto Allemandi & Co., 2004.

Gauri, K. Lal and Jayanta K. Bandyopadhyay. Carbonate Stone: Chemical Behavior, Durability, and Conservation. New York: John Wiley & Sons, Inc, 1999.

Goy, Richard J. Building Renaissance Venice: Patrons, Architects and Builders c. 1430 – 1500. New Haven: Yale University Press, 2006.

Howard, Deborah. The Architectural History of Venice. New Haven: Yale University Press, 2002.

Lynch, Gerard. Brickwork: History, Technology and Practice. London: Donhead, 1994.

Nicholas, D. D. Wood deterioration and its prevention by preservative treatments. Syracuse, New York: Syracuse University Press, 1973.

Norwich, John J. A History of Venice. New York: Vintage Books, 1989.

Pertot, Gianfranco. Venice: Extraordinary Maintenance. London: Paul Holberton Publishing, 2004.

Turkington, Alice. Stone Decay in the Architectural Environment. Boulder, Colorado: Geological Society of America, 2005.

Warren, John. Conservation of Brick. Oxford: Butterworth Heinemann, 1999.

Weaver, Martin E. Conserving Buildings: A Manual of Techniques and Materials, Revised Edition New York: John Wiley & Sons, Inc, 1997.

This is a gorgeous photo of Santa Maria del Giglio’s exterior. All but the figures are done in Istrian Stone, a marble found near Trieste, a city in Italy close to the Slovenian border. I believe this is the most widely-used stone in Italy.

Here’s a summary of some of the infromation provided in Carbonate Stone: Chemical Behavior, Durablility, and Conservation by K. Lal Gauri and Jayanta K. Bandyopadhyay:

Marble is created when limestone (think the pyramids) undergoes a metamorphic process at high temperature and pressure underground. The calcite minerals (CaCO3), grains in limestone, dissolve and reform more densely, causing a loss of porosity.

Marble is slowly damaged by rain water. As rain water falls, it dissolves carbon dioxide, CO2, from the atmosphere and reacts with the calcite (CaCO3) in marble:

CaCO3 + H20 + CO2 –> Ca2+  +  2HCO3-.

The products from this reaction, calcium ions and bicarbonate ions, dissolve in the rainwater, literally washing the marble away. Marble holds up better than limestone because its less porous: in limstone, water gets stuck in the tiny holes, causing more limestone to dissolve.

An important note here is that the weathering of marble from rainwater is very slow. The marble in Venice probably hasn’t seen much wear from the above reaction. Acid rain, caused by high levels of SO2 and NO2, speeds the reaction considerably though. I’m not yet sure if I want to discuss the pollution in Venice and its effect on the building materials. Though interesting and prevelent in Venice, its not unique to Venice, as its a worldwide problem.

Further Research:

1. I want to see if I can find water quality reports on Venice’s waterways. Is the water badly polluted?

2. I want to see if I can find scientific journal articles on marble in Venice. Surely studies have been done…

3. The photo above shows Santa Maria del Giglio, a church which has been restored, funded by unesco. Here is their site for the church. It’ll be great for my paper!

I’ve got a more coherent plan for my paper. I know now that I’m going to cover three categories of building materials: terracotta and brick, carbonate stone, and wood. For each of these I will discuss:

1) The chemical and physical composition of each material

2) How this material reacts chemically with water

3) How conservators restore and protect these materials in regards to water damage

But I want more Venice-specific information!!! Ideally, I would like my paper to raise awareness for the need for conservation work in Venice. I could either

a) see how much conservation work has been done in Venice compared to how much needs to be done (considering Venice’s budget), or

b) compare restoration versus conservation work in Venice (right now I’m leaning in this direction, thanks to Dr. Och)… I think this will flow better into the rest of my paper.

Any suggestions?

I’ve finally decided on a topic: the conservation of building materials in Venice.

Because I’m an art history and chemistry double major, I feel like this will be a great culmination point as I attempt to combine the two into a topic that will hopefully interest everyone in the class. I was straying away from an art conservation topic at first because a) I thought someone else would chose it and b) I don’t want to be an art conservator. Even though art conservation doesn’t interest me as a profession, I’ve always been fascinated by the chemical reactions that art objects can undergo in such a wide variety of environments.

 In order for art conservators to restore and protect art, they have to know every possible aspect of the material which they’re dealing with. In Venice, all the building materials are either submerged in water or face high humidity levels (high percentage of water vapor). My focus will be on how these materials respond to water and how they can be protected from the water. I’ll have to examine several building materials: different types of wood (oak, elm, larch, pine?), different types of stone (Istrian stone, marble), and materials from clay (bricks, terracotta).

MY PLAN: VERY GENERAL OUTLINE FOR EACH BUILDING MATERIAL

Chemical makeup of building material

Reactions between building material and water

How building material is protected from the water

Venice is also apparantly quite badly polluted, so perhaps a discussion of those effects on the building materials would be beneficial as well.