I want to use underglaze on a porcelain piece that will be low-fired (only because I don't want the reds to change to blue, which is what happened last time I high-fired, even with a clear coat, my red underglaze test piece). I would prefer the piece be high-fired for strength, but I've been told the porosity of the piece after high-firing wouldn't allow underglaze to take to the piece properly. Should I apply underglaze to the low-fired bisque piece or before firing as greenware?