Abstract
Clay pots have been most widely used as plant containers for ornamental plants, but few reports on the physical and chemical properties of clay pots are found. This study was intended to know some physical properties of clay pots-“Suyaki-Bachi”.
Seven types of 13.5cm size pots were collected from several pot makers at clay pot producing centers such as Tokyo, Ibaraki and Aichi prefecture. Then each test piece was cut out from a pot wall and was used either for the determinations of the permeability to air and water, the apparent porosity, the water absorption, the apparent specific gravity, and the bulk specific gravity or for the microscopic observations of pot walls.
1. Values of the permeability to air varied from the maximum, 4.70×10-4 of the products of Makabe district, Ibaraki pref. (C), to the minimum, 2.53×10-5ml•cm/ cm•cm2•sec. of those of Edogawa-ku, Tokyo (B), and the values of the products of Hekinan, Aichi pref. (E), Isohara, Ibaraki pref. (D), and the rest were intermediate.
2. Values of the permeability to water ranged from 4.70×10-6 of the products of Makabe (C) to 3.95×10-8ml•cm/cm•cm2•sec of those of Edogawa-ku (B), and the order of these values was about the same as that of the permeability to air. However, their values were between 1/100 and 1/650 of the permeability to air.
3. The order of the water absorption of the samples was almost the same as that of the apparent porosity. Samples of Isohara (D) had the lowest value, and those of Tokyo (A and B) the highest. No relation was observed between the permeability to air and water and the apparent porosity.
4. The value of the apparent specific porosity of pots of C was the highest, while there was no significant difference among the other samples. On the other hand, the values of the bulk specific gravity of the samples of C and D were higher, but those of A and B were lower than the others.
5. The microscopic observations of pore distribution in pot walls revealed that the finer pores were more abundant than coarser ones throughout all test pieces. It was suggested that pots of good permeability such as C and E had either coarser pores and some cracks or low percentage of finer pores; on the contrary, pots of poor permeability, produced at Tokyo (A and B) or Tokoname (G), had either less pores and low percentage of coarser pores or a large number of finer pores. Pots of Isohara (D), having rather better permeability, seemed to be poor in the number of pores.
