Ceramic Glaze Furnaces Go Electric as Molybdenum Electrodes Enter Building-Material Kilns

Glaze is the finish of a ceramic product, and melting quality determines the gloss, color and defect rate of the tile surface. In the past, glaze melting generally used small flame tank furnaces or down-draft kilns, with high energy consumption, large temperature swings and poor workshop conditions. In recent years competition in the building ceramics industry has become intensely commoditized, and companies hope to break out through differentiated product appearance, putting glaze melting equipment upgrades on the agenda; digital glaze printing also imposes higher requirements on the uniformity of the base glaze, and environmental retrofits of small flame kilns have further accelerated the switch to electric melting. Electric glaze furnaces have entered the picture for precise temperature control and clean melting, bringing molybdenum electrodes into the building-material kiln market as a beneficiary of glaze equipment upgrades.

Special requirements for electric glaze melting

Glaze melts contain large amounts of alkali metals, boron and other fluxing components, are highly corrosive at high temperature, and corrode molybdenum electrodes faster than most glass melts; colored glazes are also sensitive to metal ions, and electrode corrosion products must not noticeably shift the hue. Fluxing components in the glaze melt also accelerate electrode surface degradation, so glaze furnaces generally use dense, high-purity electrodes and keep current density in a conservative range, accepting a slightly lower melting rate in exchange for electrode life and glaze color stability; glaze varieties are numerous and furnace conditions switch frequently, so electrodes must also withstand repeated temperature swings. Color differences in special-effect glazes are extremely sensitive to temperature, and melt cleanliness also affects finished gloss.

Four benefits of electric melting furnaces

• Furnace temperature can be held to a narrow band, greatly improving melting consistency for special-effect glazes;
• No combustion flue gas, improving both workshop conditions and glaze cleanliness;
• Small furnaces and fast changeovers suit flexible small-batch, multi-color production;
• Melting can use off-peak electricity, at a lower cost per kWh than gas;
• Flexible shutdown: the furnace can be stopped for color changes, with low idle loss.

New opportunities in the supply chain

For electrode selection and specifications in electric melting and fiberizing of ceramic fiber and rock wool, see the article on electrodes for ceramic fiber electric melting.

Electrification of glaze kilns opens a new lower-tier market for the electrode industry: electrode consumption per furnace is modest, but there are many companies and demand is fragmented, which tests suppliers' local service and small-batch delivery capability. Some electrode makers have already launched dedicated product lines for glaze kilns, offering replacement-cycle recommendations by glaze system along with simple monitoring tools; some have also trained dedicated glaze-kiln service engineers, and the density of the after-sales network will determine order share in this market. WeiBeam.com's industry observation is that electrification of building-material kilns is an incremental space beyond glass furnaces; how well electrodes adapt to highly corrosive melts will determine how far this market can go, and fast response on small batches plus timely technical support will be the key to repeat purchases.