Siegfried Siegesmund - Monument Future

Figure 4: Simplified categories for marble: “little endangered” – “endangered” – highly endangered”.

Model calculations also permit a prediction about the decrease of the risk for a sculpture when moving it from an outdoor exposure to a depot. In these cases, the risk decreases by about 20 %, which is a considerable reduction. However, the risk in a depot cannot be completely zero either, because the sculptures still underlie a climatic effect, albeit to a lesser extent. Also, some risk factors such as low ultrasound velocity remain, even if there will probably be no further deterioration in a depot.

Overall results show that the Risk Number is an appropriate tool to all owners who wish to examine their sculpture stock and determine the risk of endangerment. Although the Risk Number does not give specific instructions about what measures are required, a high number indicates the main risks. It is therefore a useful tool in the discussion about necessary conservation measures.

The author is indebted with great thanks to Prof. Dr. Rainer Drewello (University of Bamberg), Dipl. Rest. Carolin Pfeuffer (Europäisches Zentrum für Steinmetz und Steinbildhauer) and Dipl. Phys. Wolfram Köhler.40

Delgado Rodrigues J. & Grossi A. (2007). Indicators and Ratings for the Compatibility Assessment of Conservation Actions. Journal of Cultural Heritage, 8, 32–43. doi: doi: 101016/j.culher.2006.04.007

Revez Maria J. (2016): Calculated Risk. The (In) compatibility of Built Heritage Cleaning Methods. Dissertation Faculty of Chemistry and Technology New University of Lisbon

Riegl A. (1903): Der moderne Denkmalkultus. Sein Wesen und seine Entstehung. In: A. Riegl: Gesammelte Aufsätze. Augsburg, Wien.

Waentig F., Dropmann M., Konold K., Spiegel E., Wenzel Ch. (2014): Präventive Konservierung. Ein Leitfaden. ICOM Deutschland – Beiträge zur Museologie Band 5. 96 Pages.

41

Roberto Bugini, Luisa Folli

IN: SIEGESMUND, S. & MIDDENDORF, B. (EDS.): MONUMENT FUTURE: DECAY AND CONSERVATION OF STONE.

– PROCEEDINGS OF THE 14TH INTERNATIONAL CONGRESS ON THE DETERIORATION AND CONSERVATION OF STONE –

VOLUME I AND VOLUME II. MITTELDEUTSCHER VERLAG 2020.

CNR-ISPC- Istituto per le Scienze del Patrimonio Culturale, via Roberto Cozzi 53, 20125 Milano, Italia

The use of stone in the italian architecture improved dramatically in the period 1920–40, mainly for cladding on concrete structures. New methods of exploitation and supply made available different kinds of stone, never or only locally used before. Features of the stones are detailed together with examples from Milan.

Keywords: building stone, marble, 20th century architecture, Italy.

The use of marble and natural stone in Italian architecture strongly increased in the third decade of 20th century, after a period (1900-20) when the “artificial stone”, made of Portland cement moulded in hundred of different shapes, was omnipresent (Biondelli 2004a). Many factors were involved: new architectural trends; rein-forced concrete framing where the stone lost any structural function, large availability of stone materials throughout the Italian territory; new methods of quarry working; cut of thin slabs suitable for cladding; improvement of trucks, trains, roads and railways. Moreover the stone industry was boosted by the policy (called Autarchia ) planned by the Fascist government to hinder the Sanctions of the League of Nations (november 1935); so, despite a very low import from foreign countries (i. e. blue syenite from Larvik, Norway), dozens of new quarries were opened and the ancient ones were expanded. Acting in accordance with this policy, the reintroduction of the structural use of stone, in order to reduce the import of fuel and iron, (Portland cement and reinforced concrete), was also advised, but never applied (Peverelli 1939).

The return of the marbles on the building façades was really significant in Milan, the capital of the most important industrial area of Italy. A group of young architects was ahead of a very impressive urban change, juxtaposing huge scales or massive forms of Fascist public architecture and clean outlines or simple forms of residential buildings for the capitalist ruling class, according to the thesis of “Novecento” and “Razionalismo”.

Different italian marbles never exploited in the past or only locally exploited were used in architecture, among many others. The configuration and shape of building stones were chosen according to the texture of each stone: slabs of various thickness (cladding or flooring, blending the gradation 42of colours or the arrangement of veins), moulded elements (decoration), squared blocks (pillar, column), monolithic pieces (column). The finishing of the surfaces was almost always the polishing.

Some significant stones of different nature, coming from different Italian regions (from Piedmont to Latium, from Friuli to Tuscany, from Lombardy to Liguria), are described in this study.

IGNEOUS

— Rosso Pantheon (red granite)

— Sienite della Balma (violet syenite)

— Diorite nera di Anzola (black amphibole gabbro)

— Porfido monumentale (purple ignimbrite)

SEDIMENTARY

— Zandobbio (pink dolomite)

— Ceppo di Grè/Ceppo Poltragno (conglomerate)

— Pietra di Chiampo (pink limestone)

— Pietra di Aurisina (grey limestone)

— Pietra di Finale (pink to yellow limestone)

— Rosso Amiata (red limestone)

— Portasanta di Caldana (red limestone)

— Travertino di Rapolano (light carbonate deposit)

METAMORPHIC

— Verde Alpi (green, white veined ophicalcite)

— Rosso di Lèvanto (red or green ophicalcite)

— Verde Roja (green clayey schist).

MARBLE

— Marmo di Valle Strona (grey, veined)

— Marmo di Lasa (white, veined)

— Fior di pesco carnico (grey, pink spots)

— Calacatta, Cipollino (white or green, veined)

Each stone is discussed in order to enhance: macroscopic and microscopic features together with decay phenomena caused by weathering agents (Biondelli 2004b); geological settings (Ispra 1976, Ispra 2012); quarry sites (Peverelli and Squarzina 1939, Pieri 1966); use and application in architecture, mainly in Milan, but also in other important cities (Grandi 1980, Gramigna 2001, Pierini 2017).

Igneous rock (granite). Colour: dark red, scattered of light grey spots. Minerals: quartz, potash feldspar and plagioclase. Decay morphologies: scaling. Geology: “Serie del Canavese” (Permian-Triassic) including red and grey granites barren of micas. Quarry: few kilometres west of Valperga (Cuorgnè, Canavese, Torino province). Use: mainly polished slabs for façade cladding of residential and public buildings (Palazzo INA, portals and cladding in the porch, P. Portaluppi, 1936, Milan; Palazzo del Popolo d’Italia, balcony, G. Muzio 1938/42, Milan).

Igneous rock (syenite). Colour: violet with black spots. Minerals: potash feldspar (orthoclase), plagioclase, amphibole (hornblende), biotite, piroxene (augite), quartz. Decay morphologies: scaling. Geology: Valle Cervo pluton (late-alpine, Oligocene) of the “Sesia-Lanzo Zone” (meta-morphic rocks, mainly micaschists). Quarry: near the village of Balma (valle del Cervo, Biella province). Use: polished slabs for cladding of residential and public buildings (Palazzo delle Colonne, façade made of very thick slabs with point chiseled surface in a T-shaped building with a porch of ten couples of shafts of Granito di Santo Stefano (Sardinia), G. Muzio – G. Greppi 1940, Milan).