Fundente

Fundente, in metallurgical and ceramic contexts, refers to a substance added to a material to promote fusion by lowering the melting temperature, facilitating wetting, and helping to remove oxide layers. In soldering, brazing, and welding, a fundente is used to cleanse the metal surfaces, prevent oxidation of the molten metal, and improve the flow and adhesion of the filler metal. In glassmaking and ceramic glazes, fluxes serve a similar purpose by reducing the viscosity and melting point of the mixture, aiding bonding and forming a stable glaze or glaze–metal interface.

In metalworking, fundentes can be inorganic or organic. Inorganic fluxes often contain borates, chlorides, fluorides, or carbonates, which react with oxides to form removable slags or protective films. Organic fluxes, such as rosin or carboxylic-acid-based formulations, aid oxide removal and are commonly used in electronics soldering. The choice of flux depends on the base metal, the process (soldering, brazing, welding), and the operating temperature, as well as compatibility with the filler metal and subsequent cleaning requirements.

In glass and ceramics, fluxes lower the melting point of silica-rich mixtures and influence the final properties of the glass or glaze. Common fluxes include sodium oxide from soda ash, calcium oxide from lime, and boron-based compounds such as borax. Proper use of a fundente improves fusion, homogeneity, and gloss, but residues may be corrosive or reform oxide layers if not properly cleaned after processing.