[Cavity bubbles.jpg]

Understood but the text box in the picture seams to imply the surface could heal but the bubbles on the inside are?  Maybe ok, maybe not - or is this over thinking?

[Cavity bubbles.jpg]

My understanding is bubbles quite often are not buoyant enough to rise through the viscous glaze. To some extent a successful glaze is constrained by the need to not run under the influence of gravity. Is it unreasonable to say glazes with no interior bubbles are likely rare and then  by that reasoning at what point should become  concerned?