An electric kiln often requires a new circuit, installed by an electrician. A kiln attached to the wrong voltage circuit may fail to reach the right temperatures. [2] X Research source
Glass separator (recommended) or kiln wash (adequate) can be purchased in powder form and mixed with a liquid. Brush it on in at least four coats, then wait for it to dry. Make the surface as even as possible, since tiny irregularities will show up in the glass. Alternatively, cut out kiln paper (fiber paper) to the shape of the shelf. Place it in the kiln and fire it at 1400ºF (760ºC) to blacken the paper, which can then be used as a protective surface between the glass and the shelf.
Use clay intended to be fired around 1500ºF (815ºC), or it may melt during firing.
Painted labels will survive the firing process, which makes a great design as long as the bottle remains still during firing. To avoid the chance of fingerprint impressions, wear gloves and clean afterward with isopropyl alcohol.
High temperature wire is best. Most common wires will work, but aluminum will melt and copper and brass can leave flecks on the bottle. [9] X Research source
Take extra care to keep bottles with painted labels still.
If you are using ceramic molds, you may want to use a slower heating rate to reduce the risk of cracking the molds.
This is the step that changes most, based on your bottles, kiln, and desired appearance. Consider these numbers a starting point for your first project. Always wear eye protection while looking through a peephole. If your kiln doesn’t have a window or peephole, you won’t be able to check on the bottles. [12] X Research source
The simplest method, which is usually sufficient for bottles, is to let the kiln cool gradually, never by more than -150ºF (-80ºC) per hour. If you kiln cools faster than this, you’ll need to briefly fire it occasionally to counteract the cooling. For more effective annealing, leave the kiln at 900ºF (480ºC) for a full hour. Different types of glass have different optimal annealing temperatures, so to be extra-safe you could also leave it at 1000ºF (540ºC) and/or 800ºF (425ºC) for an hour each, starting with the highest temperature first.
