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IDENTYFIKACJA MARMURU UŻYTEGO W SARKOFAGU WŁADYSŁAWA JAGIEŁŁY W KATEDRZE WAWELSKIEJ

100%

Bromowicz J., Magiera J.

Ochrona Zabytków

2006

issue 3

87-96

In an attempt to identify the marble of the tomb of King Jagiello, three kinds of marbles were used as a refernce material, i.e.: Italian Ammonitico Rosso, Austrian Roter Knollenkalk and Hungarian red. Structure, texture and mineral composition were examined and SEM-EDAX analysis was done. Very limited size of the sample available disabled the use of the optical microscope. Generally, the tomb is made of red limestone with a nodular structure and sound, non porous texture. The nodules are 1 to 5 cm in diameter. This kind of a decorative limestone being succeptible to carving and polishing is traditionally called a 'marble'. Four varieties were identified in the tomb: Variety 1. Colour is red-brownish, nodules are slightly lighter than a matrix. Indistinct parallel bedding, stylolites and ammonites can also be seen. Variety 2. Generally, red-brownish in colouring, with stronger contrast between nodules (yellow-pinkish) and matrix (brown-reddish). Variety 3. Dark red-brownish. Nodules do not contrast strongly from the matrix. Variety 4. Colour is intermediate between varieties 1 and 2. Structure, texture and colour point to the Ammonitico Rosso marble as a stone applied in the tomb. Size, shape and colour of the nodules as well as colouring of the matrix make it similar to a variety that occurs in the vicinity of Verona and is called Rosso di Verona. Hungarian marbles obviously differ from that used in the tomb. Their colouring is generally darker and more brownish. Nodules are less pronounced and less contrasted from the matrix. SEM and SEM-EDAX analyses did not appear particularly diagnostic. The sample from the tomb was generally more fine grained than the reference samples thus disabling comparison of further structural and textural features. However, similarities were detected between the tomb marble and the Rosso di Verona marble, e.g. in the texture and number of genarations of the micrite, presence of clay minerals and iron oxides. Noticeable is a presence of Al, Si and K in the tomb marble, being apparently connected with clay minerals and with products of chemical weathering. All this point to the Rosso di Verona as the most probable stone applied in the tomb. Chemical composition of the marbles form the Verona area is following: Si - 5.90% CaO - 51.31% MgO - 0.14% CO2 - 40.48% Fe2O3 - 0.66 % FeO - traces Al2O3 - 0.84% Mn - traces Average porosity is less than 0.5%, and water sorption is less than 0.1% (W. D. Grimm, R. Snethlage, 1984).

Problemy konserwacji obiektów architektonicznych z dolomitu na przykładzie barokowych bram w ogrodzeniu Katedry Wawelskiej

81%

Stępień P., Kozłowski R., Magiera J.

Ochrona Zabytków

1993

issue 4

338-346

Dolomite has been rarely studied by conservation scientists. The authors’ research has been carried out during the conservation (1992-1993) of three Baroque gates in the wall enclosing the Royal Cathedral at the Wawel Castle, Cracow, Poland. The gates were built between l6l7 and 1619, probably according to the design of an Italian architect Giovanni Battista Trevano from Lugano. Dolomite is the principal material used in these gates. The research has identified in the object several types of dolomite, showing varying resistance to weathering. The mechanism of decay involves acidic corrosion due by sulphur dioxide contained in the polluted air. In contrast to the corrosion of limestone, the corrosion of dolomite yields two reaction products: calcium sulphate (gypsum) and magnesium sulphate (epsomite). Magnesium sulphate is extremely soluble in water. It dissolves and migrates easily in the object and crystallises when the stone dries. Repeated dissolution crystallisation cycles of this salt are the main cause of the decay of dolomite. Symptoms of this decay are deep alveoli, pulverisation and flaking. Furthermore thick black crusts containing gypsum are formed in the non-washed areas. The described process of destruction proceeds differently in different types of dolomite. The porous types and/or those containing many of fine-grained components are much affected. An important damaging factor is exposure to rain water and rising dampness - the corrosion zones in the object are clearly linked to a high moisture content. Conservation of dolomitic architectural objects must involve extraction of soluble salts, specially of magnesium sulphate. Poulticing (cellulose + water) proved an efficient method, but the poultices had to be applied 5-6 times to obtain the reduction of the salt content to levels below 1 weight %. Another important point of the conservation is protection from water. In the case of the gates, new proper roofing of copper leaf and injections at the base of the gate (to obtain insulation against rising damp) were made. The whole surface of the stone was impregnated to obtain water-repellency. A solution of silicone resin (Polish product Ahydrosil Z) was used, both for water-repellency and consolidation. Another possibility is a mixture of acrylic and silicone resins (the method of O. Nonfarmale). Acrylic resins were found insufficiently resistant in Polish climate and silica esters ineffective in the consolidation of relatively large „nodules” of dolomite. It is important also to choose properly the material for repairs, avoiding the „bad” types of dolomite mentioned above. Lime mortars (with some hydraulic additions) and stone powders with a silicone preparation (Adhesil Kl) were used as filling mortars.

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2 Ochrona Zabytków

2 Magiera J.

1 Bromowicz J.

1 Kozłowski R.

1 Stępień P.

1 2006

1 1993

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IDENTYFIKACJA MARMURU UŻYTEGO W SARKOFAGU WŁADYSŁAWA JAGIEŁŁY W KATEDRZE WAWELSKIEJ

Problemy konserwacji obiektów architektonicznych z dolomitu na przykładzie barokowych bram w ogrodzeniu Katedry Wawelskiej