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Production of Calcined Gypsum or Gypsum Plaster
Published in Manjit Singh, Gypsum & Gypsum Products, 2023
Lime and gypsum are obviously different materials with different properties. Lime sets slowly by absorbing carbon dioxide from the air, whereas gypsum plaster sets rapidly by crystallising (even fully hydrated gypsum plaster sets within about a day). Also, as a lime plaster dries it shrinks slightly, while a gypsum plaster expands slightly as it sets. Historically gypsum has generally tended to be used as an additive to lime. The speed at which a mix of lime and gypsum set (which is slightly slower than gypsum on its own) and the slight expansion that occurs, are particularly useful when running cornices and other mouldings in situ.
Internal and external decoration
Published in Derek Worthing, Nigel Dann, Roger Heath, of Houses, 2021
Derek Worthing, Nigel Dann, Roger Heath
Until the 18th century, those who could afford to decorate the internal surfaces of their dwellings may well have had timber panelling fixed to the internal surfaces of walls and partitions. The purpose was to provide a suitably robust and aesthetic finish which provided a degree of hygiene and was as easy, or easier, to maintain and clean as unfinished masonry or plastered surfaces. Tapestries and other fabric wall hangings were also used but, like timber panelling, were affordable only by the wealthy. As Britain became gripped by speculative development in the 18th century, plastered finishes became more economic and far more common. Paint was an option for plastered finishes but effective painting for lime plaster relied on a limewash or the use of oil-based paints, which required the plaster to dry out for a minimum of 20 months prior to decoration.
Thermal and hygric properties of lime plasters with pozzolonic admixtures for historical buildings
Published in J. Carmeliet, H. Hens, G. Vermeir, Research in Building Physics, 2020
R. Černý, J. Drchalová, A. Kunca, V. Tydlitát, R. Rovnaníková
The most important parameter of the lime-pozzolana plaster studied in this paper compared to the lime plaster is a significant increase of both compressive strength and bending strength without using cement that was not used in buildings older than 100 years. Therefore, this plaster can be successfully applied in historical buildings instead of the classical lime plaster. However, further investigation is necessary in the direction how to further promote the effectiveness of the pozzolanic reaction on the account of calcium carbonate formation so that the increase of strength could be higher.
Automatic thermograms segmentation, preliminary insight into spilling drop test
Published in Quantitative InfraRed Thermography Journal, 2023
J. Melada, P. Arosio, M. Gargano, N. Ludwig
The tests have been performed on mock-ups and on archaeological roman plaster samples (Table 1). Mock-ups were realised using putty-lime plaster, Portland cement and plaster with powdered bricks (‘cocciopesto’). The archaeological samples come from a Roman site whose foundation dates back to the second half of the 2nd century BCE. Like all cultural heritage materials, these must be subjected to analyses that are as less destructive as possible. The reason for studying archaeological materials alongside laboratory mock-ups is to study the applicability of the SDT method also in real objects, far from the conditions of the tests subjected to regulations (UNI NORMAL [15]). In this work, the three selected samples were chosen as they are plaster monolayers carrying the various compositional differences found: pure cocciopesto plaster (RCp), painted cocciopesto plaster (RAr) and putty lime plaster (RMa).
Differentiation between Iron-II-Sulphate (Copperas) Staining and Natural Ochre Pigmented Lime Finishes on Lime Plaster
Published in International Journal of Architectural Heritage, 2022
Gesa Schwantes, Alison Trachet
Sulphur, which can also come from pollution or the use of Portland cement, can potentially damage lime plaster through gypsum formation within the plaster and formation of gypsum crusts. The formation of gypsum leads to an increase of volume which can cause the plaster to weaken and burst. The gypsum present in the copperas finishes made with lime water is bound in the carbonate layer similar to pigment in fresco surfaces. The needles are therefore embedded in the matrix, and hence fewer are visible on the surface. In this form the gypsum will not likely contribute to the deterioration of the plaster layer. However, if the copperas finish is applied with a very high amount of reactive lime in the mixture and not enough water present to form a well-bound surface layer, the gypsum crystals accumulate on the surface. These crystals are exposed and are prone to dissolve with rain water, meaning that the finish is not weather resistant. The sulphur in solution may also cause deterioration of the lime plaster surface when gypsum crystals are formed within the plaster near the inner surface.
Chemical and mineralogical investigations of lime plasters of medieval structures of Hampi, India
Published in International Journal of Architectural Heritage, 2019
Manager Singh, Selvam Vinodh Kumar, Pandurang Digamber Sabale
The acid insoluble fractions of the samples showed coarse medium-grained sand to fine-sized clay fragments. The aggregate grains were identified as potash feldspar/pink feldspar (orthoclase) to soda feldspar/grayish white plagioclase. The proportions of potash feldspar are comparatively higher to soda feldspar. The orthoclase and plagioclase feldspars show shiny sub-vitreous shape with weak planes (cleavage). The feldspar grains are intermixed with irregular-size-shaped quartz grains. The grey-colored amorphous, highly jointed, fine clay matrix partially cemented the grains. This fraction of the clay minerals also provided plasticity to the plaster. The quartz grains are easily indentified on the basis of its vitreous, transparent luster with conchoidal features. The orthoclase/plagioclase feldspar was recognized from its medium pinkish to whitish-grey-colored tabular-shaped grains. The transparent to dirty white, vitreous, massive quartz grains are in higher proportions to that of feldspar grains. Some of the quartz grains showed uneven, non-homogeneous polycrystalline nature probably due to the presence of impurity by hydro chemical reactions during their genesis. The proportions of clay size minerals are far lesser compared to other constituents. The lime binder is fine grained. The size and texture of the calcite grains formed in the plaster is probably related with the environmental condition during the period of carbonation. The aggregate grains sieved after dilute HCl digestion of the plaster is shown in Figure 3a. The typical lime plaster is shown in Figure 3b.