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Striking:

The striking of color into this, or any silver bearing glass designed to give multiple colors, is not a simple matter of, "heat it this much and get exactly the color you want". Because of the nature of striking silver glasses it can take some work and/or experimentation to achieve the various colors and they are not always perfectly repeatable. Without getting into the underlying physics of how the colors strike, the easiest way to obtain the different colors is to first understand the mechanism by which the colors form.

A very simplified explanation is that the different colors obtainable are related to the size and shape of silver particles that form in the glass during the cooling and reheating process (commonly called "striking"). Heating and cooling the glass will give different color effects based on the nature and duration of the heating/cooling cycles the glass has undergone. The growth in size and shape of the silver particles in the glass is related to that "thermal history".

Initially, we suggest simply experimenting with a flattened blob of glass at the end of a cane to see what colors and effects can be had using different heating and cooling cycles. Do not be afraid to reheat and cool the glass repeatedly to see how the colors react. If it appears that the glass has "overstruck" - typically characterized by an opaque tan color - try getting it very hot and soft in a sharp flame and then chilling it quickly. It should initially become transparent, often becoming a light or dark amber color. From here heat it slowly and gently to a dull reddish color and then cool to see what colors have appeared. This can be done repeatedly to progress through the color range.

It can also pay off to heat the glass in different flame types, i.e., reduction (lots of gas, little oxygen) or oxidizing (lots of oxygen, little gas). In some cases, along with the usual colors in the glass, an attractive metallic lustre or iridescence can be created on the glass surface. In fact, some StrikingColor silver glasses are specially formulated to maximize this iridescence. Iridescence is most easily obtained by heating in a reducing flame when the glass is below the point where it starts to soften. With these special StrikingColor glasses it usually takes just a few seconds to achieve anywhere from a light to heavy iridescent effect.

StrikingColor silver glasses will also react with some other colored glasses, which increases the decorative possibilities when using them as stringers to add an accent to one's beads. The reaction typically takes place at the interface between the two glasses, leaving a colored line dividing the two. This is most likely to happen with other glasses containing copper or cadmium/selenium.

The bottom line is - try different flame types and heating/cooling cycles to see what happens. The different color effects are not always repeatable, but they are usually attractive nonetheless. With practice and experience one can usually obtain the color range one is seeking. Experiment! And have fun!

Annealing:

Because silver glasses strike at fairly low temperatures, they can sometimes change color during annealing. Many, if not most, of the problems people have with overstriking in the kiln are due to their kiln itself and its failure to maintain a uniform temperature throughout. This problem is most likely to show up in a small kiln that has a lot of power and heats quickly. Every time the power kicks on to maintain temperature, the elements get quite hot and the temperature near them goes above the setpoint - whether the controller shows it or not. (Digital controllers can be programmed not to indicate these temperature swings.) This can pump enough extra heat into the glass to cause it to continue striking. Unfortunately, this description fits a large percentage of bead annealers on the market.

One way to counteract this is to try and keep the glass as far away from the elements are possible. Another is to turn down the heat a little bit and extend the annealing time. The best way is to find a better annealer that uses solid state controls rather than electro-mechanical or mercury relays. The absolute worst for this is an annealer that uses an infinite control for power. For those who may not be familiar with the term, an infinite control is the little dial with numbers on it that the user turns until the temperature looks right. Maintaining a steady temperature with one of these requires an act of God.

We generally recommend an annealing temperature between 930 and 960F for StrikingColor glasses. However, these are simply ballpark figures. Every annealing oven is different and an indicated temperature of 950F on one may in reality be different than the same indicated temperature on another. It is the user's responsibility to test their equipment prior to going into production with our glass.