FORMULATION OF EARTHENWARE GLAZES USING GRANITE DUST FROM SELECTED QUARRY SITES IN SOUTH-WESTERN NIGERIA

Abstract

Earthenware glazes are low temperature glazes which melt at temperature ranges between 9500C and 11000C.The composition of earthenware glazes varies depending on the type of materials selected and their characteristics. This research explored the use of granite dusts, collected from three selected operational quarry sites in South-western Nigeria, as a base material for the formulation of earthenware glaze recipes. Alongside, glass cullet was introduced as a fluxing agent. The initial processing of the granite dust and glass cullet was done through grinding and sieving using fine meshes of 40mm and 80mm respectively. The materials were further pulverised separately using a ball mill. Samples of granite dust were taken to a material laboratory at the Federal University of Technology Akure, where they were subjected to chemical analysis using Atomic Absorption Spectrometer. The composition of the glaze was initiated by weighing out component materials into batches using a triple beam balance. Line blends of the materials were used in mixing and finding the ratio (part by weight). This was achieved by mixing granite dust with cullet in a proportion ranging from 10-90%. The prepared recipes were applied on test tiles and fired to earthenware temperature to determine the eutectic point of the glaze melt from 1046oC to 1154oC. The firing temperature was monitored with the aid of Orton cones (5 & 6). From the result of the gloss firing tests, it was confirmed that the use of granite samples alone could not suffice for the development of glazes that can melt at earthenware temperatures. Hence, there was the need for an addition of glass cullet to lower the melting temperature. Ikere granite sample mixed with cullet of 30-60% blends yielded the most promising result for the development of earthenware glazes as it melted at 1060oC with a glossy appearance. The blend of granite dust and cullet could only produce good earthenware glazes when all granite samples were mixed with cullet ranging from 30-70%. This study established the viability of granite collected from the selected locations as an active base material for the formulation of ceramic glaze. It reveals the mineralogical composition of granite as desirable raw material for formulation of ceramic glaze that can be mass-produced with economic advantage over stoneware and porcelain glazes.