I have a piece of slip-casted (not by me) greenware that is now fired into bisque. It had a small patch of slip and it appears that during the firing process this little patch fell out, or evaporated, or some such. Anyway, it has a small irregular gouge about 1/16" deep by about 1/16" to 1/18" long. I’d like to somehow patch this before I glaze/fire it. Suggestions?
Is Bisque-Fix my best option? And if so, do I need to refire it before I glaze it?
Yes, Bisque-fix is your best option. While some recommend refiring to bisque, I normally just glaze right over the patch. Given that you probably don’t have any slip to mix with it to adjust the color (Bisque-fix is stark white), that should work. I suspect that if you mixed some slip with it to make it less white, that should probably be re-bisqued.
I’ve had quite a bit of trouble with breaking dragon wings, so I have repaired several items using Bisque-fix, and proceeding straight to glaze. It doesn’t take it long to harden, so I don’t feel the need to let it set for more than a few minutes.
You don’t necessarily need to re-bisque. A reason that you might choose to is if you are using a lot and want to reshape after a second bisque to further refine and blend the patch in. But if you rib it well, dry, and sand it to a good result while the fix is still green, then you can glaze as is and fire to the final cone.
Different glazes respond in a variety of ways to BF, so just be aware you might have a color or even texture difference. Also, BF is very white, if you have a darker clay body, you can tint the BF with some slip made of your clay or if you feel confident, a touch of stain.
Edit: What she said! Beth beat me to the punch. 
You can also repair with paper-clay slip, or paper-clay. You would make your paper-clay slip etc using your clay body, so color issues of the repair would not be a problem.
Archie Bray also makes an excellent repair product called ‘Bray Patch’.
You can contact them online and order.
But – we’ve got a jar of Bisque Fix sitting on the shelf with the underglazes…
Have you seen it lately? I plan to come to DMS tomorrow to make my patch. Thanks.
I went back to check, and we’ve even got a new-ish jar!
Thanks!! 