Food Test - Vinegar or Acetic Acid

This test is to see if a glaze is durable in an acid food environment.
It can be done with vinegar or acetic acid - my preference is to use 4% acetic acid, as this is more repeatable than variations in the acidity of different vinegars, and also corresponds to what is used in the official standards.

Equipment Needed

  • Pot(s) or test tiles to be tested. You need 2 for each glaze, one to be tested and the other, with an identical clay body and glaze, to be used as the reference to compare against after the test.
  • Vinegar or a 4% (by volume) solution of acetic acid

If testing tiles, a plastic container to hold the acid and test tiles

PPE

None needed.

Procedure

  1. If testing the glaze inside a bowl, pour the vinegar or acid into the bowl and cover
  2. If testing tiles, pour the acid or vinegar into the plastic bowl, and add the tiles glaze side up. Ensure that the tiles are fully covered. Cover
  3. Leave for 24 hours at room temperature
  4. Remove the test piece(s), rinse off in cold, fresh water and pat dry
  5. Compare the glaze against the reference piece. Ignore any crazing as this is likely to be due to water absorption by the pot causing expansion, rather than a chemical attack on the glaze. Use a magnifier to see more details, e.g. a magnifier app on your phone, possibly with a magnifier lens, or under a microscope.
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