The chapel in the Small Tower at Landštejn is one of the few Romanesque monuments in our territory. Both the original plaster with fragments of paintings and engraved and painted graffiti and the unique Romanesque mortar floors have been preserved. In 2017-2022, extensive research and restoration of the chapel's interior was carried out.
The main objective of the survey (2017-8) was to identify the causes of the acute degradation of the plasterwork and to propose possible solutions. Extremely high concentrations of water-soluble salts were found in the plaster due to several hundred years of leakage into the masonry. Sensors were placed in the chapel to monitor relative humidity and temperature. Salts increase their degradation activity quite substantially with frequent fluctuations in humidity. On the advice of the climatologist, the chapel's openings were completely sealed.
The main objective of the subsequent intervention on approximately 300 m2 of Romanesque plaster was to reduce the concentrations of water-soluble salts, remove unsuitable and degraded additions and provide the plaster with a suitable mortar. The restoration intervention began in 2019 with the conservation of the plasters and paintings and repeated desalination poultices, which continued until 2022.
A mixture was developed for the desalination poultice whose properties were adjusted so that it could absorb maximum salts. Therefore, not only sand was used as a filler for the desalting mixture, but innovatively (on the recommendation of the technologist), marlstone, which has an open capillary structure. The mixture had to be adjusted so that it would not shrink, would not separate from the substrate and could be applied with a plastering gun. The desalting process was monitored by continuous sampling of the plaster and the desalting poultices. The analyses showed that the long-term poultices (about 4 months) were significantly more effective. A total of 5 cycles of kaolin-marlstone long-term desalination poultices were carried out in the chapel. On average, there was an 83% reduction in the concentration of water-soluble salts in the surface layers, with the first three poultices being the most effective. The use of a new formulation of a highly capillary-active spray desalination poultice was quite innovative.
The chapel floors were desalinated with an absorbent backfill of marlstone, sand and lime hydrate. Samples taken after 3 years showed that the backfill had absorbed high amounts of water-soluble salts. This is a completely new technology combining prevention with protection. At the same time, the application and especially the replacement of the backfill is very simple. They therefore have great potential for further use. The idea of implementing desalination in the form of backfill is particularly innovative, as is the recipe itself.
Furthermore, the plaster was consolidated with lime nanosuspensions and grouted with grouts in three coarsenesses. The mortars were made as a replica of the original material, from sand from a site in a nearby forest. Additions to the render were made only to the extent necessary, so as not to interfere. The chapel is currently accessible on a limited basis with climate control.
Although this is a rescue of simple historical plasterwork, which is not so attractive at first sight, it is a major contribution to the restoration of architectural heritage, even in an international context. This is what should be considered above all in this category.
