Refiring Bisque info needed?

[Judi Souder]

I have many pots that I created using cone 5/6 white stoneware years ago, but never glazed them.  Many of them have collected dust and "yuck",  and I am inclined to refire them to cone 04 hoping the dust will burn off.  I am about to fire a 04 bisque load and want to add them to my firing.  Any suggestions will be appreciated!  Thanks

[Hulk]

Good question!

Some of the dust burn off may leave substantial ...dust?

My suggestion would be to dunk the wares in clean water, scrub off with a large sponge and/or, perhaps a brush, then rinse.
From there, it shouldn't take particularly long for the wares to dry out, then glaze and fire per your usual process.

You might hold off on the whole load, however - perhaps pick a few to glaze fire - just to check how your glazes and the "older" wares behave together, afore committing the entire load.
 

I wash and rinse off my bisque as a matter of course.
Almost all my ware features some chattering. When the glaze doesn't "wet" all the way to the bottom of the chatter mark, the glaze will pull back, leaving a holiday, hence, I rinse, with attention to the chatter marking...

Edited June 19, 2023 by Hulk
and

[Judi Souder]

Thanks for your reply.  I always wipe down my piece before glazing, but these pieces are really dirty.  I'll try the wash method and let them  dry in the sun:)

[Rae Reich]

Use a brush when washing dusty crevices. Leftover dust will interfere with the glaze adhesion. 

[Hyn Patty]

I've refired old and dirty bisques many times before.  Clients send me pieces from all over the world that are decades old and been handled with oily hands, etc.  I refire these clean as a matter of standard procedure before I attempt any glazing so that I know the bisque is super clean before I proceed.  I agree, wash off what you can but if the clay may be porous at all, do NOT SOAK in water.  Water can dissolve salts and calcium out of your clay so merely wash up with a scrubby and a little soap, then rinse.  Set aside to dry.  I use a heater fan to help such pieces dry faster.

If you don't want to wait days to be sure the bisque is dry enough to fire, I go ahead and load it up into the kiln and fire on a low temp pre-soak for a couple of hours  before going ahead with the new bisque firing.   Cooks off any moisture left but do it slowly.  Obviously that is not an issue if the ware is fully vitrified  but I advise it for porous earthenware.

If after firing you are left with any dirty grey ghost marks you may sand the bisque to remove it if the glaze or underglaze you plan to apply isn't opaque enough to conceal it.  Alternatively you can also add a layer of opaque white underglaze and fire that before you proceed with color.