This is a cone 6 transparent base glaze. It contains frit, silica, kaolin, wollastonite. Almost all glazes have materials that are slightly soluble and over time these can form scale on the sides of the bucket or even precipitate particles into the slurry. The defects here are those scales. Before dipping a production piece in any glaze that has been in storage it is a good idea to assess it first to see if it needs to be sieved.
Sieves are important in ceramics for removing particulates and agglomerates from glaze, engobe and body slurries.
Crystals or crystalline particles will often form over time in ceramic glaze slurries that contain slightly soluble materials.