BOROMAX® USER MANUAL

During the last six years the lampworking world has seen many changes worldwide. Glass Alchemy, Ltd. (GA) has ardently participated. During this period GA has conducted thousands of experiments, worked with dozens of artists and traveled to countless studios and production shops. GA has had the envious backstage passes to observe the lampworking movement explode. As you, the user of Boromax™, continue to explore the limits of your art we at Glass Alchemy, Ltd. must push the boundaries of what our products can endure. Not only have we produced new colors since the last edition of our User Manual, we have tweaked, altered, rethought and reengineered many of the colors to be brighter and to withstand more time in the torch and kiln—in short to survive the new rigors that the contemporary artist demands.

This, the 3rd addition of our Boromax™ User Manual, is full of cutting edge (even revolutionary) information that we hope you will find helpful (and even stimulating).

Glass Alchemy’s mission statement “Enhancing the world through vision, creativity, and innovation” has kept us on the forefront of new color development and methodology in the field of colored borosilicate art glass. GA is proud of its role as a leader in the science behind the evolution of the art of lampworking.

WORKING WITH GLASS ALCHEMY BOROMAX® COLORS

Prior to the revolutionary work at Glass Alchemy, there was little reliable information available to lampworkers on the science of using pigmented glass. Many flameworkers could not get their silver colors to strike, colors would turn “muddy,” rubies would become livery and greens would turn red or crack. A method for adjusting the flame to neutral (neither reducing nor oxidizing) and verifying that it was indeed neutral did not exist. We at Glass Alchemy have spent a great deal of time and effort to develop methods and information for borosilicate glass artists based on scientific fact.

As you read about the various colors, please keep in mind that the spirit, effort and research at Glass Alchemy has created most of the colors used in borosilicate today. The bright Crayon colors were first developed by Henry Grimmett at GA and remain the highest quality and widest selection available. The Sparkle colors were first developed by GA and tested two full years prior to introduction. We feel our Sparkle colors contain the most consistent aventurine flakes available in an extremely stable base. The GA chrome opal and transparent glasses represent the finest, least problematic and most researched chrome glass on the market. As you read about the polychromatic glasses you will discover there are many options available when working silver colors to achieve your desired end results. If you have not yet tried all of the Boromax™ colors, we urge you to experiment inside and outside of your favorite palette. As you experiment your technical questions are welcome—simply e-mail tech@glassalchemyarts.com for diagnosis of a problem or to understand how to repeat the great results you just got.

Not only has GA created revolutionary new colors, the team continuously improves production techniques resulting in consistent, straight, round cane in 4mm, 7mm and 12mm diameters along with frits of uniform size and shape that are free from tramp metals (contamination).

PHASE SEPARATION, CRYSTAL GROWTH AND NUCLEATION

The process of manufacturing borosilicate glass involves the melting of sand grains (silica crystals) with various fluxes added to achieve the proper coefficient of expansion (COE) along with colorants. This is followed by cooling the mass at a given rate to achieve a certain transformation temperature (tg) at which point the batch is “vitrified” or free of crystal structures—it is now glass. (This is the state you, the artist, receive the glass.)

By controlling the application of heat while lampworking you have the ability to remanufacture this mix of materials. The materials stay well mixed at high temperatures because of the energy involved. However, as you allow the temperature to drop below the softening point to the annealing point the glass appears to harden. The large molecules can no longer move freely and create a rigid framework, yet, the smaller molecules can still move around and separate out into pools of similar materials. For this reason the rate at which you cool each individual piece of glass determines many of its properties. If held at temperatures near 1150° to 1250°F for extended periods the process of separating into pools of similar materials can become detrimental to your work piece. This process of segregation is known as “phase separation”. In some extreme circumstances this molecular pooling has the potential to create several new types of glass in your work piece often leading to “divitrification,” a situation where crystal structures start to form. When performed with knowledge and a trained hand, one can use this process to their benefit. Controlled phase separation can be used to strike certain colors by creating nuclei and allowing the growth of crystals to generate various colors. This is a critical concept to understand, it has different implications with the different pigments discussed in this manual.

Growth of crystals is a time/temperature relationship. The growth rate is slower at temperatures below the annealing point and reaches a peak at temperatures around 1250°F. Above 1250°F the growth rate drops off again, much like a bell-shaped curve. At the annealing range of 1035°F to 1065°F (depending on the brand of clear or color you are using), the artist has tremendous control of the color outcome. If the glass is taken to a white heat (very liquid state), the crystals will melt and the glass will unstrike. GA recommends flame striking for silver colors and kiln striking for ruby colors.

Ruby colors, which are created with a reduced copper as the colorant, also strike because of crystal growth, but the course of action is slightly different than the silver colors. In the colorless form, the copper is distributed as colloidal atoms, called pyrosols. As the glass is heat-treated the copper starts to form crystals, and as the heat soaks deeper into the glass, chromophores (visible color cells) form and the glass becomes a deeper red. If the chromophores grow too rapidly or with varying heats, a non-uniform dispersion of particles can be generated. If the chromophores form in various shapes and sizes, it will result in uneven absorption of light wavelengths. This condition is referred to as “liveryness”. This is why kiln striking, to ensure even heating at the proper temperatures, rather than torch striking is recommended.

TORCH SETUP

When working with many colored glasses the flame chemistry is very important. It is possible for the fuels to react with the glass and change the color or other characteristics. Some reactions can even cause the glass to crack. For this reason GA suggests that you work your colors in a neutral flame unless you are trying to produce a definite effect that requires an off balance flame.

Obtaining a neutral flame can be complicated by a poor torch setup. If you play with the mathematical formulas that give us insight into the behaviors of the gasses as they pass through the torch, you will discover some very helpful information. Consulting the Bernoulli Equation (energy per unit volume before the torch = energy per unit volume after the torch) we discover that as the gasses pass through the torch the velocity increases and the pressure drops (for a fun graphic example, see www.home.earthlink.net/~mmc1919/venturi.html). In other words, increasing the pressure increases the speed at which the gasses pass through the working zone a.k.a. the heat transfer zone. The thing to keep in mind about the softening of the glass is that it is the transfer of heat from the burning gasses to the glass that is important. This happens at the point of contact of the glass and flame—the balance of the flame is heating the room. The most efficient transfer happens when the available energy in the heat transfer zone is high. If the gas is whizzing by the glass without contact you are running up your fuel gas bill. The goal is to increase the heat transfer while decreasing the amount of gas you are burning. Low pressure (slower velocity) and more volume (available energy) at the point of impact results in more transfer of heat.

In general, large diameter hoses and lower pressures work better than small diameter hoses and high pressures. Larger supply hoses insure that you have enough gas available to meet the demand of the torch especially when you open the valves more turns. The lower pressure allows you to open the valves wider because you are not generating high velocities and the evil twin, turbulence. Lower pressure also allows you a wider range of flame mixes when adjusting the valves. You use less fuel overall and more energy (measured in BTUs) reside in the heat transfer zone.

Small diameter hoses can result in pulsations of the flame. Increasing the pressure of the fuel gas to prevent these cavitations often results in a longer reducing zone in the flame forcing you to work further out in the flame. Increasing the oxygen flow to compensate for the increased fuel gas will result in high velocities. High velocity flows are not as efficient in heat transfer and can result in the dulling of the glass from carbon impingement. Smaller torches can be set up with short runs of standard twin welding hoses, which are readily available in most hardware stores. Larger torches, on the other hand, should be equipped with larger diameter hoses, so that the gasses they demand are available and obtaining a neutral flame is possible. Larger diameter hoses are most easily found at hose specialty shops.

SETTING THE NEUTRAL FLAME

Glass Alchemy recommends that you always work with a neutral flame—it helps maintain consistency and vibrancy in your work. A neutral flame also helps to prevent the cracking in chrome colors associated with reduction and eliminates the problem of ionic colors changing from one “species” to another, i.e. changing from green to red, or from blue to gray.

To test for a neutral flame, Glass Alchemy suggests that you heat a rod of 987 Amazon Night to a warm orange glow and allow it to cool. The resulting color of the rod will indicate whether or not your flame is neutral. You have a neutral flame if the 987 did not change color. If the stick is a light sky blue or has a metallic sheen, the flame is reducing (has unburned propane) and needs to be adjusted. The most common fix (say 70% of the time) is to decrease the propane content.

• If the surface of the glass looks like an oil slick, decrease the propane at the torch
• If the surface of the glass is heavily metallic, decrease the regulator in 1⁄4 pound increments
• If the surface of the glass is sky blue, it is especially reducing. Decrease the propane at the regulator in half; i.e. decrease from 2 pounds to 1 pound of pressure.
  

In the remaining cases the proper course of action is to increase the oxygen flow to burn the “extra” propane in the flame.

Note: By definition reducing agents lose electrons. Carbon is an oxidizing agent because it gains an electron. Some lampworking books, especially European, refer to the nature of the flame and call a flame rich in carbon “oxidizing,” which is scientifically correct. The American lampworking model, for whatever reason (probably because a handful of artists created the convention based on the fact the oxygen was turned down), refer to what the flame does to the rod (not to the chemistry of the flame) and call the same flame as above a “reducing” flame. When reviewing the literature, it is important to understand that these two conventions exist. Again, from a scientific point of view a carbon rich flame is oxidizing (because it wants oxygen) and it reduces the glass by taking oxygen from the glass. We elected to continue with the American lampworking convention of calling the flame “reducing” because of its widespread use in the field and will continue this convention until such time as a group such as GAS or ISGB elects to standardize the definition within the industry.

THE NUMBERING SYSTEM