Standard StrikingColor glasses are "104 compatible". "104 compatible" is a rather ambiguous term meaning that these glasses are generally compatible with other popular flameworking glasses considered "104 COE" such as Moretti/Effetre, Vetrofond, etc. However, due to the fact that glass compatiblity is dependent upon more than COE alone, as well as the fact that we have absolutely no say in the quality control of other manufacturers (and not even all of their own colors are compatible with each other), we at StrikingColor cannot guarantee our glasses to be universally compatible with those from any other manufacturer. If you will be mixing with glass from another manufacturer, compatibility testing with that glass before going into production is strongly encouraged.
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.
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.
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!
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!
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.
We generally recommend an annealing temperature between 910 and 920F for StrikingColor glasses. However, these are simply ballpark figures. Every annealing oven is different and an indicated temperature of 920F on one may in reality be quite 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.
Many people like to anneal their beads by loading each one into a hot annealer as soon as it is made and then starting the final soak and ramp down cycle at the end of the work session. Because this results in the first beads loaded getting the longest heat cycle it is imperative that the initial holding temperature used while working be low enough that the silver glass does not overstrike. A holding temperature of around 880F will normally be low enough to prevent kiln striking, while still being hot enough to keep the beads from cracking. Once the last bead is finished the kiln should be turned up to annealing temperature and the normal annealing cycle started. When using standard striking silver glass, the loading/holding temperature should always be lower than the final annealing temperature in order to prevent unwanted color changes in the kiln.
Having become very, VERY tired of seeing the oft-quoted but completely erroneous claimed annealing temperature of 960F for Moretti/Effetre glass, I decided to compile a list - with references - of a variety of different soft glasses, some relatively common and others, like Steuben crystal, rare. The numbers below were either published by the glass manufacturer or measured in the glass lab at Corning Incorporated. I didn't just pull them out of my... ummm... imagination.