Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed

167 work of coloured cement. The uniform fields also chiefly consist of coloured cement, the yellow fields having, however, a layer of fresco-paint above the coloured cement. Here and there occur for the rest blue and red lines, friezes and lists round the fields. The named yellow paint has come off or has grown incoherent. When moistened with water the whole of the yellow layer of plaster can be removed with a spatula which cannot be done for instance with the black layer of plaster when moistened. Below the yellow paint the yellow coloured cement is in many places seen to have nearly lost its colours. The pictorial representations have also to a great extent lost the colours; all round the coloured plaster is seen to be disintegrated, and everywhere the cement plaster both in the fields and the pictures is full of cracks. It may be taken for granted that the latter have contributed to the principal destruction of the plaster planes in the course of time; water and dirt penetrated into the fissures, and on the freezing of the water they widened out, while the dirt occasioned the for- mation of fungi in many ways instrumental in the plaster and colours being ruined. It is well known that the fissures are derived from the con- traction of the cement plaster during the setting. Before the Con- gress for testing materials in Paris in 1900 Prof. Henry Le Cha- telier laid the results of a series of experiments begun by him some years before on the shrinkage of the absolute volume of cement mortar during the setting and shortly before published in Bull, de la Soc. d’Encouragement 1900, p. 54. Before the same Congress the director of the Danish States Testing Labora- tory laid some experiments made by the Laboratory partly to show this contraction, partly to prove that the contraction could be counteracted when treating the plastered planes with Kessler’s Magnesia-fluate1). The Report VI2) of the Laboratory treats, however, not only of these matters, but also of several others, thus, researches on the alkalinity of various sorts of cement and researches on the best reaction against this alkalinity. Among the remedies tested for this purpose fluate proved to be best adapted *) Last Volume of the Report of the Congress, p. 183, Summary of a Report by G. A. Hagemann and II. I. Hannover. 2) Translated into German in »Baumaterialienkunde« 1903, Nr. 12 and 1904, Nr. 7, 8 and 11—12.