To Attempt to Glaze, or Not to Glaze
All potters have accidents every once in a while. It is why it is so important to build a healthy potter's attitude.
The first thing to discover is how vitrified your pots are. There are two quick-and-dirty tests you can easily do.
- The Ting Test: Flick the pots with a fingernail. Do they ting or do they sound kind of dull? If they ting, they are at least partially vitrified and the glaze may not apply well. A dull sound means the pot will probably take the glaze without too much trouble.
- The Wet Finger Test: Wet your finger and lay it on the pot. If the water is wicked up quickly, the clay body is probably still absorbent enough for glazing.
In the event the pots are too vitrified, some suggestions are below.
Possibility: Glaze Interior Only
Try glazing the interiors only of the pots and re-fire to the clay-glaze maturation temperature. By glazing only the interiors, if the glazes do detach, they will be caught by the pot itself.
You can decorate the exterior surfaces with stains, but I would not use any engobes, or underglazes, since the lack of proper adhesion will likely effect engobes and underglazes, too. You may wish to experiment with overglazes, knowing that they will come out differently than normal. This is because overglazes were developed for use on the smooth surface of a glazed pot; the unglazed surface is much rougher.
Possibility: Apply Glazes but Prepare for Problems
If you are a hardy individual, you may want to try applying glaze both inside and out, and fire to maturity. Brushing the glaze on may work better than dipping. In Either Case! If you choose to try this, make certain to protect your kiln and kiln shelves.
Glazes are known to crawl or even simply fall off the pot when there are adhesion problems. Place all ware with glaze on the exterior onto heavily kiln washed bisqued tiles or dishes with shallow rims. I prefer shallow dishes, as they catch glaze better in my opinion.
Possibility: Smoking
A possible way to finish overfired bisqueware is to try smoking the pots. To do this, place the pots one to three at a time under a metal trash can with smoldering combustibles such as straw or dried weeds. Only do this outdoors. Not for functional ware. Hopefully, even though your pots are not kiln-hot anymore, you will get some smokey pattern effects.
Possibility: Waxing
You can use floor wax (or similar product) to create a satiny finish on pottery. Apply the wax to the pot then buff until you get a gloss. Not for functional ware.
Before waxing the pot, you can add decoration. For example, you can wax the pot after smoking or you could use watercolors or thinned acrylics to paint on a design before applying the wax.
Possibility: Crayons
Another possibility is to apply wax crayons to the pots. Not for functional ware! First, either make sure your crayons are made with wax (not all are) or do a trial piece. Draw the designs on the overfired bisqueware. Warm with a blow drier until the wax begins to melt or become very soft, then push the colored wax around to emphasize or create designs. Buff each piece when it has cooled.