Eli5: Why shouldn’t you put home made ceramics (a mug, for example) through the dishwasher? If they can withstand the heat of a kiln, surely a dishwasher is fine?

Question

I mean, I put them through the dishwasher sometimes anyway, but I’m told I shouldn’t? 🤷🏻‍♀️

In: 5331

Answer 1

Potter here…

This is a complicated subject. Well-made and tested homemade ceramics can go through the dishwasher just fine. However, a dishwasher is a very rough environment. Most potters, who recommend handwashing only, do so because the pot is less likely to get banged around. Stress cracks, formed by banging against another pot in the dishwasher, can cause the entire pot to crack when hot liquid is poured into it, not to mention chips and dings to the rim.

Other considerations: Dishwasher detergent is very basic. If the glaze is not tested for basic conditions (rare in foods) a dishwasher can cause the glaze to fade over time. Also, there are certain finishes, such as gold enamel, that will fade badly in the dishwasher. Finally, if the clay body is not fired to low absorption, a dishwasher can cause water absorption in the clay, which can cause mold and excessive heating in the microwave.

So, for dishwasher, microwave safe ceramics, the clay body and the glaze need to be tested together for fading under both acid and basic condition, no enamels applied, and the clay body should be fired high enough to ensure a low absorption. It is highly recommended that each clay body be tested by the potter prior to use. It’s not uncommon for manufacturers to label a clay cone 6-cone 10 when the clay is not really suitable for functional use when fired to cone 6.

I’m probably forgetting something, but these are the use cases that affect my work.

EDITED: Corrected a term. It’s “basic” not “caustic”. Thanks to ScienceIsSexy420 for pointing that out.