Om Materialprøvningens Udvikling i Norden
Og om Statsprøveanstaltens Virksomhed

168 to coloured cement planes, being at the same time instrumental in rendering the plaster tight. The named report treats further of the researches made by the Laboratory to find suitable pigments to mix up with cement mortar, as it is well known that many pigments are destroyed by this intermixture. The researches were made at the Testing Laboratory by a sub-committee consisting of the gentlemen named in Note 1, p. 167, and elected by the committee, and this sub-committee had various restoring experiments made on loose flakes, among these in the spring of 1900 a larger sample of the pictorial represen- tation containing 8 various sorts of coloured plaster. This sample was able to stand all through the summer in sunheat and rain without cracking and, it is true, that in the following winter a great many very fine fissures occurred in 3 of the 8 sorts of coloured plaster, but the 5 others were exposed to the sunshine and rain of 3 summers and the frost of 2 winters i. e. to up to about 50° Centigrade and down to 12—13° Centigrade below zero without cracking and without the named fine fissures in- creasing apparently in number or size. A restoring trial was later made by the magistracy of Copen- hagen by much the same method on the museum itself at the ordinary entrance. But bad fissures soon occurred here. The reason can be sought for in various circumstances, for instance in the intermixture of pigments having not been the same, in the hardness of the smoothing having differed, or in some contrac- tion of the decoration having taken place while the experiment was made with the loose flake, this not having been discovered by formation of fissures, because perhaps the flake itself has also contracted. The very difficult problem has therefore not yet been solved, but in one direction, at any rate, there seems to be a reliable result, as series of durable pigments having na- mely been found. g. Experiments with Partly Replacing Lime in Lime-Mortar by Moler. At the first series of experiments a mortar was be- gun with which contained 8 per cent dry calcic hydrate. As sand was used a mixture in equal proportions (by weight) of normal sand and down sand. In the named mortar the half- part of the calcic hydrate was then replaced by moler.