The cone 03 porcelain cup on the left has 10% Cerdec encapsulated stain 239416 in the G2931K clear base. The surface is orange-peeled because the glass is full of micro-bubbles that developed during the firing. Notice that the insides of the cups are crystal-clear, no bubbles. So here they are a direct product of the presence of the stain. The glaze on the right has even more stain, 15%. But it also has a 3% addition of zircon. Suppliers of encapsulated stains recommend a zircon addition, but are often unclear about why. Here is the reason, it is a "fining agent".
This is a type of stain manufacture that enables the use of metal oxides (like cadmium) under temperature conditions in which they would normally fail.
Suspended micro-bubbles in ceramic glazes affect their transparency and depth. Sometimes they add to to aesthetics. Often not. What causes them and what to do to remove them.
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.