Document gbGBNGe27DvqgX7OmqZvaEgkq

J.F. Smith J.L. Kimberley Subject; "Case for Forced Circulation in Glazing Kilns" In accordance with recent conversations it is understood that you will proceed to press appropriately on the following position as concerns glazing of ceramics. It is clear that the "leachability" of lead from glazes is closely related to proper time and temperature in the ovens. Industrial as well as hobby or art craft glazing of ceramicware is commonly performed at temperatures ranging from l800F to 2100F in electrically heated kilns. Their sizes range from 1 cubic foot to 500 cubic feet or more of interior volume. Larger ones include provisions for the glazing of several shelves of products per load. Forced circulation of air within these ovens is uncommon. It is t^&likely that temperature gradients throughout the working space of the oven are frequently in excess of plus or minus 10$. Glazing temperatures are commonly measured by the partial collapse of specially formulated and prepared cones which start to collapse when the prescribed temperature is reached and maintained for the proper time. With thermal gradients undoubtedly existing in any kiln that does not incorporate forced interior circulation, dangerous variations may frequently exist. It is recommended that appropriate steps be taken to require that manu facturers of glazing kilns (not now so doing) incorporate forced circulation into their design and manufacture. While it is recognized that the hobbyist or art crafter is concerned with economy, and that the incorporation of forced circulation in the kiln will add to the cost of his equipment, the proper glazing of ceramicware is a matter of vital importance to consumer safety. Forced circulation would Incorporate a substantial degree of LIA-76999 insurance and hence a highly desirable step. Forced circulation for uniformity of temperature in annealing or heating muffles is standard practice in the metal producing industry. Outstanding examples are to he seen in the stress relief heat treatment common to the manufacture pf brass articles to insure against "season cracking" and in the annealing and heat treating of aluminum products where plus or ml nna 2F is consistently and economically achieved. As this campaign progresses, please Keep me closely up to date on developments. JLK/gt cci D.M. Borcina J.F, Coley J.'fi. Kimberley Executive Vice President L!P,-77000