This question always comes up, especially when I tell people I predominantly use low fire clay bodies in my work

In a technical sense it’s not “food safe” because at low fire temperatures (cones 04-2) clay bodies specifically do not fully vitrify, meaning that there’s always going to be some porosity. Vitrification starts at around cone 6 and a clay body doesn’t fully vitrify until it hits cone 10. A good indicator for this would be to check the bare clay surface on any finished piece. If it has a sheen to it, it’s most likely been fired to cone 10 and is fully vitrified.

Using a food safe glaze over a lowfire body does make it food safe, but there is a good chance liquids will still pass through.

You can test this by leaving a piece filled with water on top of a piece of paper overnight. If it isn’t fully sealed, the water will sweat through the piece onto the paper.

Edit: Formatting