Ceramics (cups, bowls plates, jugs, figures, etc) are divided into three major categories: stoneware, earthenware and porcelain. This post is a very quick identification to which of the three is that figurine in the antique store, bowl in the estate stale, or coffee cup your kitchen cabinet. It is usually easy to make an identification, though there will always be some gray areas where it’s hard to tell if something falls into one or the other.
Porcelain, which has that signature refined, smooth, thin, ‘dainty tea cup’ look, is the only of the three categories that is translucent. This means if you hold up the item to the light you can see light come through. If you pass your fingers between the item and the light, you will see the shadow of your finger pass by.
Stoneware, which is opaque (doesn’t let through light), tends to be heavy and substantial. It can look more basic, handmade and primitive— ala that old time country folk art jug. Anywhere the object is unglazed the clay is darker, usually dark grey but also sometimes light brown, sometimes with specs in it, and has a rough texture, as it if was made out of a chunk of clay in middle school pottery shop. Stoneware cups, bowls, plates and similar usually have unglazed bottoms where you can see the rough, dark material. Due to being cooked at a higher temperature, stoneware can hold water even when unglazed—- thus the unglazed bottoms.
Earthenware, which is also opaque, is the most common form of ceramics. Most of your ‘department store’ dinner plates and coffee cups in your kitchen are earthenware. Unlike stoneware, earthenware is not waterproof when unglazed. This means earthenware is almost always glazed all over, including on the bottom. This is particularly true for a cup, bowl or jug that is intended to hold liquid. On an earthenware cup, plate or bowl the entire item will be glazed except for a thin white or off white rim at the bottom. That part is left unglazed so the item doesn’t go sliding across the dinner table. At this unglazed area, or any other glazed area such as a chip, the material is milky or chalky (unlike the coarse dark stoneware material).
Just remember that an earthenware cup, bowl or plate will be glazed on the bottom (except for the chalky rim), while heavy stoneware is unglazed on the bottom and has a darker, rough texture.