These are the steps that I follow to fire glass. , meaning clear glass, such as wine glasses, Polish glass, which is heavy bottom of thick glass and the opal glass used for oil lamps.
The glass that I am talking about has no lead in it. Do not fire leaded glass this way because it will sag. I believe leaded glass can go no higher than 750 degrees faherenhiet if it is standing alone. I am sure that if you fire hotter it will have to be supported in some way with a mold.
I try to not fire glass more than 4 times - especially heavy bottom vases.
It has been my experience that the heavy glass bottom has cracked during the fifth firing.
Stem glasses: First determine which side is heavier..the stem or the goblet. Most times I fire the goblet down.
Keep glass at least 2 inches away from elements.
The glass should not touch each other.
Do not stack glass, unless you are firing a flat piece. Flat pieces can be stacked on shelves with enough space between the shelves for the heat to be evenly distributed.
If you have a short chamber in your kiln, I suggest that you do not fire a large piece. You should have air space at the top of the kiln. If the space is small....Remember, heat rises.
I always leave the kiln lid propped at least 1 inch from start to finish. This does not increase the firing time.
1100 to 1150 degrees Fahrenheit is the required heat for glass firing maturity or .022 cone.
I fire with the dial on medium for 1/2 hour. I then turn the dial up to a medium high, meaning I never turn the dial to high.
I never flash the kiln, mainly because I do not like to manipulate the kiln cover because I am afraid of getting burned.
My kiln has a kiln setter and when the latch falls, that is the end of the firing.
Using a pyrometer is an excellent way of firing glass. You are sure of the temperature.
The fired glass should not be removed from the kiln until it is completely room temperature.
Willoughby's Glass Enamel
#200 white glass enamel is to be used for glass and to be fired to .022 cone, no higher. This enamel can be mixed with your glass paint to color it. The enamel will be pastel in color because you are adding the colored paint to a white substance.
Use Willoughby's Enamel Media to mix the enamel powder a to a dry consistency and thin with pure gum turpentine. The same directions apply for soft or hard string.
Willioughby Enamels are for Porcelain not Glass.
Willoughby enamels are in dry powder form. Mix with Willoughby's Enamel Media to a thick dry paste, thin with pure gum turpentine. If you want to make round dots, it should slide from your pallet knife in a soft string, if you are going to make scrolls it should be a firmer string. Apply to glazed porcelain or to bisque china using turpentine as your medium. Dry at normal room temperature overnight and fire to .019 for soft body ware and to cone .018 for hard body ware. The hotter the firing the more the enamel will relax.
NOTE: To paint with enamel, mix the White Enamel with Mineral Oil (thick). This is very effective if you are painting on clear glass.
The majority of Lusters are all the same color before they are fired. I lean toward the old way of having a brush for each color. I store them in a test tube with a rubber stopper in which I drill a hole and then insert my brush. I place a small piece of cotton in the bottom and place a drop of clove oil on the cotton and it helps not having to clean the brush and the brush remains soft.
Luster should be applied lightly. If it is applied too heavy it will ash and you loose the shine of the porcelain. I also pad it with sport sponge wrap if I am attempting to cover a large area. I brush it on and then pad it. This procedure can be done in between firing.
Most lusters mature at cone .018 - but if you fire them hotter you will obtain different effects.
Dispersing luster: Dispersing Agent move luster extremely fast. I do use Dispersing Agent to disperse luster. I have tried many other agents and I find that the dispersing agent does the best job.
Clean Turpentine: This product moves luster slower. Resist all that you want to remain the same and allow to dry completely or use a hair dryer. Put a few drops of turpentine on the piece and then drop your luster. If you desire it to move quicker, use more turpentine.