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1
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Niszczenie i konserwacja średniowiecznych wątków ceglano-wapiennych w Krakowie

100%
Weber J., Kozłowski R.
Ochrona Zabytków
|
1995
|
issue 1
77-80
EN
A prevailing mechanism of the chemical weathering of bricks exposed to the polluted atmosphere of central Cracow is an uptake of sulphur dioxide by a solution of calcium carbonate abundant in the mortar. The subsequent cycles of dissolution, transport and precipitation lead to filling cracks and cavities in the bricks with gypsum as well as to the formation of relatively thin gypsum crusts on the surface. The latter, always incorporating soot and dust particles, constitute a characteristic black patina of the brick buildings. The effectiveness of water repellent treatment in protecting the lime surfaces against acid deposition has been demonstrated by using artificial weathering in a humid atmosphere containing SO2 .
2
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Zastosowanie tynków szerokoporowatch do konserwacji zasolonych murów na przykładzie sieni wjazdowej Zamku na Wawelu

100%
Kozłowski R., Stępień P.
Ochrona Zabytków
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1994
|
issue 3-4
273-280
EN
The Entrance Hall provides main monumental acces to the Arcade Courtyard of the Castle. The Hall acquired its present architectural form in the first half of the sixteenth century when its western larger part and two stone arches were added to an older, Gothic structure. Earlier conservation work at the Renaissance arches revealed the presence of considerable amounts of soluble salts, migrating into the stone from the brick walls of the building. The salts contained deliquescent nitrates and chlorides which gave rise to a permanent high moisture content in the walls, specially during periods of a high relative humidity (RH) of air. Hence, a systematic analysis of the salt content became an integral part of a planned conservation of the Entrance Hall in 1993. The methods employed involved high performance liquid chromatography (HPLC) for quantitative salt analysis and the determination of water vapour sorption at several RH values to establish moisture levels in the materials. The results revealed a very irregular distribution of deliquescent salts in the building, with salt accumulations in the ceiling and the southern wall. Since desalination of the walls could not be considered, because it is time consuming and uncertain, broad pore, water repellent plasters were used on the areas with a high salt content. Plasters of that kind are produced now by industry as a dry preparation, to be mixed with water on the building site. In Germany they are known as „Sanierputze”. The plasters in question exhibit high porosity and low resistance to water vapour diffusion combined with high water repellency which inhibits the migration of salt solutions to the surface, and thus wet stains and salt efflorescences. The evaporation zone is located within the plaster and salts accumulate in the plaster pores. The first stage of the conservation programme involved the removal of previous 20th century cement plasters and repairs. Then „Porosan-Trass-Sanierputz” from Keim was laid locally on salt laden areas. The remaining fragments were covered with traditional lime-sand plaster. At the end the entire plastered surface was coated with a thin finishing lime-sand layer and rendered water repellent with a microemulsion of silicones in water (Funcosil Hydroimpraegnierung from Remmers). Full conservation of stone and brick elements, which remained exposed, was carried out, including a water repellent treatment with the same silicone microemulsion. The conservation was finished in May 1994. The water repellent, broad pore plasters proved useful in the conservation of salt laden walls. They have provided an aesthetic finish free of usual symptoms of salt decay. It should be borne in mind, however, that they are materials with a strong cement binder and therefore they should not be used on brick masonry of high historic value. Their use in the Entrance Hall has been restricted to areas with high salt content and combined with traditional lime technology.
3
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Problemy konserwacji obiektów architektonicznych z dolomitu na przykładzie barokowych bram w ogrodzeniu Katedry Wawelskiej

81%
Stępień P., Kozłowski R., Magiera J.
Ochrona Zabytków
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1993
|
issue 4
338-346
EN
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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