In ceramic glaze formulation, increasing feldspar results in which effect on fusion?

• A. Strong color
• B. Better fusion
• C. Higher viscosity
• D. Faster cooling

Answer: (B)

In glaze chemistry, fusion means the glaze melt becomes a smooth, flowing glass that bonds to the ceramic body during firing. Feldspar acts as a flux, providing alkali oxides (potassium and sodium) that lower the melting point and break down the silica network in the glaze. Adding more feldspar increases these fluxing oxides, which creates more liquid phase at the firing temperature, allowing the glaze to flow and fuse more completely. That’s why increasing feldspar leads to better fusion.

The other ideas aren’t the primary effect: color is mainly driven by colorants and glaze chemistry in general, not by feldspar alone; higher viscosity would be the opposite of what feldspar does, since it lowers viscosity; and cooling rate isn’t directly controlled by feldspar content in the context of fusion during firing.