Fusing with Spectrum Glass

Spectrum Glass can be a great choice for fusing. We have a wide variety of colors that, for the most part, don't change when fired. The uniform flatness of the sheets facilitates stacking without trapping air. And, Spectrum is quite reasonably priced.

We do not, at this time, sell a "factory-tested" line of products for fusing, so compatibility testing is your responsibility. However, we think you'll be pleasantly surprised at how many of our products are consistently compatible with each other. To simplify your testing, we have established our clear smooth cathdedral, stock #100SFS, as a consistent standard that you can dependably test against. #100SFS has also been specially formulated to resist devitrification, even after multiple firings, so it's a great clear "cap" for your projects.Our coefficient of expansion is 96.

We recommend the Reynolds Interface Compatibility Test, as outlined in The Fused Glass Handbook (revised edition), by Gil Reynolds. (Distributed by Fusion Headquarters, 15500 NE Kincaid Rd., Newberg, OR, 97132, Tel (503)538.5281 . The "Stressometer" test, as described in Glass Fusing, Book One also works very well.

Kiln Shelf Preparation

You should experience no significant difference with Spectrum glass by using the kilnwash and shelf preparation techniques you normally use. We get fine results using Hot Line Shelf Primer and following the instructions on the label. If you mix your own kilnwash, we recommend a mixture of 40% Kaolin and 60% Alumina Hydrate by weight. We do not recommend shelf primers that contain calcium carbonate. Fiber papers work fine with Spectrum, and should be pre-fired to 1100°F to remove any organic binders.

Overglaze Instructions

Spectrum glass requires an overglaze when heated above 1300°F (704°C). "Super Spray," also from Fusion Headquarters, produces excellent results. "Spray A" works well, too. Hints:

• CLEAN GLASS THOROUGHLY with warm water. Oil or grease spots can be removed with ethyl alcohol. Spray or brush an even coating of spray to the tops and edges of all glass pieces that will be exposed during firing. It may be necessary to spray top-layer pieces before assembly in order to coat glass edges. THICK spray trapped between glass layers will not fire clear.
  
• "Super Spray" needs a slightly heavier coating than does "Spray A."
  
• Spray black glass heavier than you do other glass colors.

Using Iridescent Glass

At bending and slumping temperatures, Spectrum Iridescents produce very interesting effects. However, the coating can withstand temperatures only up to about 1400°F (760°C), and then, the results vary. Maximize your Iridescent effects at high temperatures by fusing with the Iridescent surface against the kiln shelf, and minimizing time spent above 1400°F.

Our friends at Uroboros have Spectrum-compatible Iridescent glass available that will not burn off, even at full-fuse temperatures. Ask your glass supplier or contact Uroboros at (503) 284 4900.

The firing and annealing steps outlined here are those we've found most successful for projects two or three layers thick (about 1/4to 3/8 inch). We've included both fusing and slumping guidelines for small (4 inches), medium (12 inches) and larger (20 inches) projects. Of course, these are only guidelines, not strict rules. You'll need to adjust your times and temperatures based on the characteristics of your equipment, the actual size and thickness of your project, and the aesthetic effects you wish to achieve.

Free Advice: Be sure to clean all sides of your glass pieces thoroughly before stacking. If you're using a thick ceramic mold for slumping, increase annealing and cooling times. In general, acquire great patience; vast amounts of work have been lost due to removing glass from the kiln too early. Wait until you can safely place the project on your bare belly.

Definitions:

RAMP TIME: The time required for kiln temperature increase or decrease. Use the amount of time stated in each step for your kiln to transition from its current temperature to the next stated SET POINT, in consistent degrees per minute

SET POINT: The goal kiln temperature in any given step.

SOAK TIME: The length of time to maintain the current SET POINT before executing the next step.

FLASH VENT: A quick-cooling step to be executed when the fuse or slump reaches VISUAL MATURITY, according to the judgement of the artist. Instructions:

• FLASH VENT for Fusing: TURN OFF KILN POWER. Open kiln for 8 seconds, then close.
• FLASH VENT for Slumping: TURN OFF KILN POWER. Open kiln for 3 seconds, then close.
  

25 Aug'99
 
© 1999 Steve Ackman (any-browser adaptation)