Steatite products from magnesium silicates have recently wide uses as fine refractories, electric insulating materials, etc. The authors wish to study fundamentally on this problem, by using talc, serpentine, magnesite or magnesis and silica, etc., which are to be plenty obtained in South Manchuria. The results of the preliminary studies are reported in the present peper, which are here briefly abstracted from the original Japanese paper, as following:
(a) Raw materials were collected, i.e., (1) Talc from South Manchuria and Korea, (2) Serpentine from Korea and Japan, (3) Shuganseki (one of magnesium hydrosilicate) from South Manchuria, (4) Some samples of steatite products from Germany and Japan, etc., and all these samples were tested on their chemical compositions and specific gravities. The results are shown in the following table 1.
Table 1. Chemical Compositions and Specific Gravities of Raw Materials and Test Specimens
Fom these results, it is clearly seen that (1) talc samples A, B and C from South Manchuria have good quality, but Korean talc D has not so good quality, (2) serpentine samples are of bad quality, (3) Shuganseki from South Manchuria has good quality and is other form of magnesium hydrasilicate, having different compcsitions from talc and serpentine, (4) steatite specimens of Japanese products have nearly same chemical compesitions to calcined talc, (5) German specimens, so-called, “Steatit-Perle, Magnesolit or Isolier-Perle”, are not steatite origin but porcelain like alumino-silicate products, etc.
(b) Talc A was powdered to the fineness passing through 4900 meshes/cm², and several series of preliminary tests were carried out by using this powdered talc A with or without small amount of elutriated fire clay (Kibushi clay) or starch. The test pieces were moulded to small plate (Length: 60mm, Bredth: 30mm and Thickness 15mm) by hand or oil press, applying 50kg/cm² and 100kg/cm², and dried first in air and then in thermostat of 105-110°C. The burning temperature was, in the present-study of preliminary test, adopted 1250°C, and the higher temperatures will be used in the next studies. The test pieces were compared on their drying and burning shrinkages, specific gravities, porosities mechanical strength, (bending or transverse strength, or modulus of rupture), etc. The results are shown in the following table 2.
Table 2. Results of Preliminary Tests on Steatite
From these results, it is clearly observed that (1) the smaller the amount of moulding water is, the smaller the shrinkage of drying and burning, and the weight decrease are, (2) the higher the moulding pressure is, the smaller the srinkage and the weight decrease, and the larger the mechanical strength are, (3) the addition of 10% of fire clay increases the mechanical strength, but on the contary decreases the density, etc.
(c) The samples were tested on their physical properties, e.g., specific gravity, linear expansion, weight increase or decrease, mechanical strength, etc., by the hydrothermal treatment in an autoclave of 10atm. water vapour and about 180°C for 3 hours. But it could not be observed any remarkable changes.
(d) The authors are now further studying by using the results from these series of prelimary tests, on the steatites, which will be obtained by moulding with higher pressure, by burning at higher temperatures and longer hours, by adding other plastising materials, etc. And then it will be studied on the electrical propertied and also the thermal changes of the preparad steatites. These results will be reported in their next reports.

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