The present invention relates to a substrate composition comprising from about 20 wt % to about 60 wt % of a water-soluble and/or water-dispersible polymer and from about 20 wt % to about 80 wt % of a water-soluble inorganic salt. The substrate composition of the present invention has a median particle size of from about 1 micrometer to about 100 micrometers and comprises less than about 10 wt % of water-insoluble material.