ABSTRACT In the paper, the lime-barium and lime-zinc glazes used in Southern and Eastern Africa Mineral Center (SEAMIC) ceramic unit in Tanzania were investigated for the production of high temperature raw glazes in Cameroon. The base Seger formula used was 0.3KNaO, 0.3CaO, 0.4ZnO or BaO; xAl2O3 and ySiO2. Different Al2O3/SiO2 formula ratios for glossy and matt glazes were tested with raw materials from Cameroon and Tanzania. In the Cameroonian glazes, a local pegmatite (quartz, microcline, albite) with low coloured oxides replaced an albitic feldspar in the Tanzanian glazes. The other materials were kaolin, limestone, silica and barium carbonate or zinc oxide. The glazes were tested at Seger Cone 7 (1240℃) on stoneware slabs (made up of the same feldspathic glaze material: 18%, silica sand or quartz 27%, ball clay 40% and kaolin 15%) from both Tanzania and Cameroon materials. From results obtained, zinc oxide acted as a more vigorous flux than barium carbonate at cone 7, which is obvious in the glazes with pegmatite (with high quartz content). At a Seger formula of Al2O3/SiO21:10, transparent glazes were obtained. In these glazes the alumina content was lower and when increased to higher Seger ratios 1:4.7 - 8.7, the gloss was lowered to matt-luster due to fine crystal formation.
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nullU. Melo, N. Billong and E. Kimaro, "Lime-Barium and Lime-Zinc Raw Glazes with Raw Materials from Tanzania and Cameroon," Materials Sciences and Applications, Vol. 2 No. 10, 2011, pp. 1392-1398. doi: 10.4236/msa.2011.210188.
 L. Fr?berg, T. Kronberg and L. Hupa, “Effect of Soaking Time on Phase Composition and Topography and Surface Microstructure in Vitrocrystalline Whiteware Glazes,” Journal of the European Ceramic Society, Vol. 29, No. 11, 2009, pp. 2153-2161.
 W. James and A. W. Norris, “Some Physical Properties of Glazes,” Transactions and Journal of the British Ceramic Society, Vol. 55, 1956, pp. 601-630.
 H. Norster and J. Danish, “Glazes-for the Self-Reliant Potter,” GATE, Vieweg Publication, 1987.
 R. Behrens, “Glaze Projects―A Formulary of Leadless Glazes,” Ceramics Monthly Magazine Handbook, Professional Publications, Belmont, 1992.
 Th. Rehren, “A Review of Factors Affecting the Composition of Early Egyptian Glasses and Faience: Alkali and Alkali Earth Oxides,” Journal of Archéological Science, Vol. 35, No. 5, 2008, pp. 1345-1354.
 H. Desirena, A. Sch?lzgen, S. Sabet, G. Ramos-Ortiz, E. de la Rosa and N. Peyghambarian, “Effect of Alkali Metal Oxides R2O (R = Li, Na, K, Rb, and Cs) and Network intermediate MO (M = Zn, Mg, Ba and Pb) in Tellurite Glasses,” Optical Materials, Vol. 31, No. 6, 2008, pp. 784-789. doi:10.1016/j.optmat.2008.08.005
 J. Malins and K. H. Tonge, “Reduction Lustre Glazes and Pigments,” British Ceramic Transactions, Vol. 92, No. 2, 1993, pp. 83-88.
 J. R. Taylor and A. C. Bull, “Ceramic Glaze Technology,” Pergamon Press, New York, 1986.
 E. Tejiogap, “Etude de l’Action du Fluorure de Potassium sur Quelques Argiles Camerounaise du Groupe de la Kaolinite,” PhD Thesis, Université de Yaoundé I, Yaoundé, 1996.
 E. M. Levin, H. F. McMurdie and F. P. Hall, “Phase Diagram for Ceramists,” American Ceramic Society, Columbus, 1956.
 A. A. Omar, A. W. A. El-Sheunawi and G. A. Khater, “The Role of Cr2O3, Li and Their Mixtures on Crystalline Phase Formation and Microstructure in Ba, Ca, Mg Aluminosilicate Glass,” British Ceramic Transactions And Journal, Vol. 90, No. 6, 1991, pp. 179-183.
 C. Vittel, “Pates et Gla?ures Céramiques,” Edition Delta SA, CH-1800 Verey, 1986.
 J. E. Marquis and R. A. Eppler, “Leadless Glazes for Dinnerware,” American Ceramic Society Bulletin, Vol. 53, No. 5, 1974, pp. 443-449.
 J. Deboos, “Living Dangerously: Barium Glaze Research Project,” British Ceramic Transactions, Vol. 98, No. 1, 1999, pp. 35-38. doi:10.1179/096797899680228