Often glazes do dry up in storage. It is not spoilt as glazes are minerals mix chemically combined under heat to fuses onto ceramic . Adding water might help to reconstitute glaze to paintable texture. Too much water the fired glaze will be patchy and desired color will not be true. Adhesion too is bad and may even craze crack. This is more apparent on high fired dense stoneware or porcelain.
Glaze diluent improved adhesion, better brush strokes coverage with consistent coating. Add water, break up glaze lumps soak overnight if necessary followed by addition of diluent progressively till texture is smooth and paintable. Hand mixing or mechanical mixing with Jiffy mixer helps. Predilution diluent with water before mixing if necessary. As usual glaze over in 2 to 3 coatings as per glaze recommendation. Complete in one sitting as soon as previous coat is about dry.
Allow reconstituted glazes to dry completely before firing. Taking the usual precaution of stilting or application of wax resist to prevent glaze over run and shelf damage.
