underglaze on top of fired clear glaze?

[Susan Herre]

I have  two pieces and am applying underglaze on top of glaze.  Will it work?

First piece is Laguna Ward's Red Cone 06 earthenware with cone 06 clear glaze (already fired.)  Trying to fix something, so I added some underglaze and plan to add more cone 06 clear glaze.  Do you recommend two firings -- one for the new underglaze, one for the additional clear glaze?

Second piece: Laguna White B-Mix Cone 10 with cone 6 clear glaze (already fired.)  Again, trying to fix something, so I added underglaze and plan to add Cone 6 clear glaze to the new underglazed bits.  Do you recommend two firings -- one for the new underglaze (maybe at low-fire 06 level)  and then high-fire cone 6 for the clear glaze?  

Thank you for your thoughts. 
Susan

[Bill Kielb]

All ideas are workable. Since these are fixes my suggestion is to try. Underglaze over glaze is sometimes known as inglaze but is usually applied at the time of glazing. The repairs I have successfully used have been all lowfire and generally fire down. Refiring a cone six piece already fired to cone six will have an effect and be somewhat stressful. Overlaying lowfire glazes is common, generally safe, and several refirings can be done with less worry about over stressing the ware. You can find many examples of layering and refiring work with lowfire glazes such as stroke and coat. Likelwise China paints are surface treatment and fired to about 017, so multiple firings and less stress. These can also help with decoration and repairs.

To your idea of clear overcoat, I have successfully used a lowfire clear as a last step in the process to repair a midfire item. The lowfire clear appeared to give reasonable encapsulation and strength to the finished product. Your trial of methods will yield results, hopefully intended. Of corse I needed to be sure the clear expansion characteristics matched the body, else risk crazing etc....

Fire down is my general rule for maximum safety to the ware but lots of folks refire with success. Cone 10 clay fired to cone 6  may end up too porous for functional wares but that's a whole different discussion.  

[Susan Herre]

thank you for your thoughts.