Increased amount of powder in zinc phosphate cement mixture will cause:

Factors affecting solubility: Powder-liquid ratio: Thicker mixes show less solubility. Water content of liquid: Any change in the water content is accompanied by increased solubility. Effect of moisture contamination: Premature contact of the incompletely set cement with water results in the dissolution and leaching of the surface. Varnish application over the exposed cement margin is beneficial. Ref: Manappalil P: 91,92