Iris Lustre or Mother of Pearl liquid overglaze is applied on top of your already glazed and fired ceramic piece which is then fired again at a relatively low temperature. Mother of Pearl is easily applied and its appearance will vary with the type of glaze used underneath. NOTE: Colorobbia uses an oversized bottle so it may not appear full. It is, however, filled and sealed with 25 grams of Mother of Pearl or Iris Lustre. In business for more than 75 years, National Artcraft is a name you can trust. Iris Lustre or Mother of Pearl liquid overglaze is applied on top of your already glazed and fired ceramic piece which is then fired again at a relatively low temperature. Mother of Pearl is easily applied and its appearance will vary with the type of glaze used underneath. A bottle contains 25 grams of Colorobbia Mother of Pearl overglaze luster. NOTE: Colorobbia uses an oversize 1 ounce bottle so the bottle may not appear full; but it is filled and sealed with 25 grams of Mother of Pearl.