USE OF OX GALL IN PREVENTION OF CRAWLING OF GLAZES

H. Spurrier
1922 Journal of The American Ceramic Society  
The crawling of glazes m a y be entirely prevented by the use of ox gall in solution. The action is probably due to the lessened surface tension. Some time ago, it was desired to glaze over an underglaze decoration in which the medium was oily so that a single fire might suffice instead of the usual two-fire method. At first the prospect of success did not look very rosy and any effort in this direction seemed foredoomed to failure. It occurs, however, that artists sometimes use a preparation
more » ... use a preparation of ox gall to cause water colors to "take" on paper that has become greasy. Accordingly an ox gall preparation used for art purposes was secured and it was determined to try it out. The material was a light yellow limpid liquid, quite clear and without any fluorescence. A small quantity of this liquid was added to the glaze and the pieces were dipped, the glaze so treated covered well and gave promise of good results. The pieces were fired as usual and came out very well. This circumstance led to an effort to find other materials that would do the work and hot be so expensive as the artists' material. Many and diverse materials were tried out and only one other was found that in any way served the purpose, and this none too well. The material was sulphonated castor oil also known as Turkey red oil or soluble oil. No further work was done in this connection for some three years, until recently. A bad case of "stripping" brought the former work to mind. Owing to the presence of oil in dust-pressed ware, a certain colored glaze could not be made to cover, and the most aggravated stripping occurred in the kiln, rendering the pieces entirely unsuitable. In the meantime, a new source of ox gall was secured. This time the gall was in the paste form but very much cheaper, and is known as inspissated ox gall and was supplied by a large drug house in Detroit. On using this material such startlingly good results were obtained that some investigation was made in order to ascertain the underlying cause for the results. It was noted that an aqueous solution of the material seemed to show a much lessened surface tension, and while this would undoubtedly help the aqueous glaze to cover the greasy or oily surface it was somewhat difficult to see how this should affect the firing behavior so strikingly. In order to test out the influence of the lessened surface tension, a cake of paraffin wax was dipped into a glaze containing a small quantity of the ox gall. On withdrawing the cake a thin even layer of glaze had become attached to the wax which was laid down flat to see if the film would "break." This however did not take place, and the glaze dried up completely having
doi:10.1111/j.1151-2916.1922.tb17897.x fatcat:aecrlfdiivfnllog2kx53jfufe