Set in Ceramics

I made my first efforts in ceramics, not focusing so much on making precious pieces(yet) but rather getting a feel for the way one works with the clay.
When the clay is semi-dry it carves smoothly in what one might call "shavings," but is easier to clean up the small details once completely dry. I used oxides as an under-glaze for these pieces, but the oxide mostly disappeared when fired. I am trying to prevent this with some newer pieces by doing a firing to 900degrees C in between the under glaze and actual glaze.