Glazed rim

The term "Borde" is a very old German word and is hardly used today. The "Borde" describes the upper end of a body to which something is attached. Shipping, for example, uses the term "on board" derived from this. In the language of porcelain makers, the upper edge of a hollow body, i.e. the upper edge of a bowl, cup or mug, is referred to as the "rim".

The term "rim glaze" or "rim-glazed" is a specific quality feature of porcelain. It means that the rim has been completely glazed - or, depending on the thickness of the wall of the crockery, reglazed. For most consumers, this quality feature is not initially a decisive purchasing criterion until tea cups or coffee mugs become stained at the rim and residues of oils, tea or caffeine can no longer be rinsed off.

In the hotel, catering and communal catering sectors, on-board glazing is therefore practically a must! Visible residues - especially around the upper edge of the mouth - must not be allowed to remain and rob the guest of the feeling of cleanliness and hygiene.

Many people will now ask themselves why not all crockery items have a rim glaze, or believe that rim glazes are always guaranteed on high-quality porcelain. However, a look in grandma's crockery cupboard teaches us better: Even the expensive teacups on the old crockery from Meissen, Hutschenreuther's Dresden Rose or Rosenthal's Maria Theresia have no rim glaze! Even many bone china teacups from high-quality tea brands do not have a rim glaze. Why is that?

The answer is simple and obvious. The handle of the cup is quite heavy compared to the body of the cup. If the cup is fired in the kiln standing on the base ring, the weight of the handle will deform the round shape of the cup. Depending on the wall thickness of the body and the shape of the cup, this may be more or less. In simple terms: the cup "bends" and becomes oval.

However, if the cup is fired on the rim, i.e. on the mouth rim, the cup body is protected from deformation by the larger contact surface of the cup body. This leaves the unglazed rim. Many manufacturers of household porcelain - especially with thin body thicknesses - only polish the rim.

For commercial use, please pay attention to the suffix "glazed on rim".

This also explains the sometimes considerable price difference between a teacup and a coffee mug. While drinking cups can often be produced using a single firing process without any problems, high-quality and "good" porcelain teacups have to be fired up to 4 times. The endeavour to achieve "thin walls" often imposes limits on porcelain due to its hard firing. Softer types of ceramic such as bone china, new bone china and other imitation porcelain can be fired at a lower temperature and therefore have less deformation, but a significantly lower density and less hardness.