On a new form of reagent against perspiration effects on shoe materials
In a discussion of a series of tests connected with the fastness of colours on textile fibres, Villavecchia (1918) mentions the use of neutral ammonium acetate or common salt solution for measuring the colour resistance to perspiration. Thus in the case of coloured cotton, this is immersed for 10 min. alongside an equal quantity of white cotton yarn in a 0·1% aqueous ammonium acetate at 80°C., and the extent of colouring of the yarn as well as the degree of stripping of the coloured sample noted after drying without rinsing. An odd number of degrees of fastness is arbitrarily assigned to the coloured specimen according to the result, e.g. V degrees if neither the original tint nor the whiteness of the yarn is changed. Similarly with linen, hemp and ramie. For coloured wool both methods are used, viz. with sodium chloride and with ammonium acetate. In the former case, the alteration in colour is noted after simply dipping the wool in salt solution and allowing to air-dry out at room temperature. In the latter case, an equal quantity of white zephyr wool in addition to the white cotton is present. V degrees in all cases are stated to be conventionally adopted between industrial associations and dyestuff manufacturers for materials which are fast enough to reveal no change whatever in the testing bath. For coloured silk there are no precise data, and usually it is immersed in distilled water for several days to ascertain if any colour is lost.
Further Studies on Foot Perspiration and Its Action on Footwear
In continuation of previous work involving accentuated effects of perspiration on chrome upper leather, the present paper records observations of such effects in more complicated conditions. Thus, effects were studied at varying temperatures and pH of tans, buffered tans, buffered perspiration, buffered perspiration coupled with tans, buffering material itself and soap solutions. Particular reference is made to the influence of basicity on the stability of the chrome complex against perspiration in such buffered chemical systems. Brown grain leathers are considered as well as box and willow calf. A method is evolved for minimizing spueing risks or the formation of Glauber's salts in the vamps of worn footwear, by appropriate treatment of the skins before cutting up into shoe upper components. Finally, some foot-bath experiments and the dark, cracky grain of worn insoles are discussed from the general point of view of perspiratory action on footwear. The writer acknowledges with thanks the assistance of Messrs L. P. Huggett, B.Sc., A.I.C., and W. H. F. Jackman, B.Sc., A.I.C., in the routine analytical work. His best thanks are also due to the Director and Council of the Research Association for permission to publish.
Shape and surface texture of molten droplets deposited on cold surfaces
When a molten droplet impacts on a cold surface, the interaction between solidification and fluid dynamics can lead to different shapes and surface textures of deposited droplets. This article presents an experimental study on deposition of small droplets (39 μm diameter) of molten wax ink on solid surfaces. Our results show that both the final shape and the surface texture of deposited droplets are extremely sensitive to deposition conditions, which include initial temperature of droplets, type of substrate surface and distance between substrate and printhead. Different surface textures are observed and shown to depend on the thermal and flow histories of ink droplets during the process of impact. A test using crystalline wax reveals crystallization as one of the major factors in determining the final texture.