Here is the original test cup (r), and one pulled from the last firing (l). The first cup was refired to cone 5, the second to cone 6. I was worried with the extra heat that the overglaze brushwork would bleed or run, but it didn’t.
One thing I like about this overglaze deco is that it allows me a ‘second chance’ for decoration when refiring this kind of work. The other is that it allows for finer detail showing up in the final product. Underglaze iron tends to get absorbed into the glaze and/or clay body, so the finest lines become obscured or transparent.