Clear glaze and transparent glaze are the same thing, and it is the glaze most studios use in the largest volume, because everything decorated needs it. It is also the least forgiving: an opaque glaze hides a poor surface and a thin patch, and a clear one shows every one of them.
What a clear glaze is for
Two jobs. It seals and makes functional a body that would otherwise be porous, and it protects and brightens decoration underneath, which is why underglaze work is nearly always covered with it. On a dark body it reads as a gloss over the clay's own colour, which is an effect worth using deliberately rather than treating as second best.
Why it shows every flaw
Because you can see through it. Pinholes, bubbles, uneven thickness, dust under the glaze and the marks of a brush all remain visible in a clear coat, where an opaque white would swallow them. That makes preparation and even application matter more here than anywhere else on the glaze shelf, and it is why beginners often think their clear glaze is faulty when their bisque was dusty.
Clear over colour
A clear glaze changes underglaze colours slightly, usually deepening them, and a thick coat can move a colour noticeably. Test the combination rather than the glaze alone: an underglaze that looks correct on a bisque tile and wrong after glazing has not failed, it has simply been seen properly for the first time. Some colours are formulated to be used under clear and say so.
Buying it in volume
Clear is the glaze to buy in the largest sensible quantity or to mix from raw materials, because it is used faster than anything else and it stores indefinitely. Suppliers list clear and transparent glazes in both earthenware and stoneware ranges; as always, the range must match the body rather than the preference.
Questions people ask about clear glaze
Is clear glaze the same as transparent glaze?
Yes. The names are used interchangeably by suppliers and manufacturers for the same product.
Why does my clear glaze look cloudy?
Usually applied too thickly, or slightly underfired. Both leave unmelted material scattering light through the coat.
Does clear glaze change underglaze colours?
Slightly, usually deepening them, and a thick coat changes them more. Test the combination rather than each separately.