Warm Glass Renaissance

by AMACO brent

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Modern Technology Brings Back an Ancient Glass Art Form with Amaco Glass Select Fire Kilns. Contemporary glass art is reviving an ancient glass medium.Warm glass, which is commonly known as glass fusing or slumping, is an ancient artistic technique. Historians have found traces of both methods dating back to the second millennium BC in Mesopotamia. Glass mosaics, valued in Greek and Romans civilizations, were considered equal to silver and gold as precious materials. By the third century AD warm glass fell out of favor, eclipsed by a new blown glass technique. It was not until the emergence of the European Arts and Crafts movement, in the late nineteenth century, that warm glass was revalued as a decorative art form. Today, contemporary artisans have rediscovered these ancient techniques. Popularity of warm glass is being fueled by current trends in design and by the ease of modern kilns such as the AMACO/EXCEL Glass Select Models. The following simple instructions for AMACO/EXCEL Warm Glass Kilns, along with an introductory project, will lead you through basic terms and materials associated with contemporary warm glass techniques.

Basics of Contemporary Glass

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Basic Instructions for Contemporary Glass: The composition of contemporary designs can be easily made by the random arrangement of chosen elements. The following project involves experimentation with 1.6mm and 3mm glass sheets with full fusing and slumping techniques. Firing programs for full fusing, tack fusing and slumping are made up of heating/cooling segments, where glass is heated, then cooled to produce a variety of effects for different thicknesses of glass. The firing program for all methods takes approximately 18 hours; each program consists of 8 segments, cool/heat/cool. Tack fusing produces a relief-like surface accomplished by firing at a higher temperature. For tack fusing programs, refer to the AMACO/Excel GSF-670 and GSF-045 manuals. For full fusing and slumping methods, follow these steps. Slumping will require a second 18-hour firing.

Full Fuse Glass Method: Cut Glass

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Using fiberboard or a carpet square for your work surface, choose an assortment of colored fusible sheet glass, threads and confetti to create a simple composition.

  1. Choose a primary base piece or bottom piece of glass. All other glass will lie on top of this piece. (Begin with a small piece to experiment with until you get comfortable with the process.)

  2. Score and cut/break the base piece to the size and shape you want. This is easer than it sounds. Take your pistol grip cutter and press firmly down on a predetermined line on the smooth side of the glass, and push away from yourself.

Snap Glass

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Then using glass pliers, line up the arrow on the pliers with the score, and apply pressure to the grip. The glass should snap along the scored line.

Arrange Pieces of Glass

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Score and cut smaller pieces of colored glass and arrange a composition on top of the base piece. Enhance the design with threads, confetti and frits. Use a small amount of white glue that has already been thinned down (50% water/50% glue) to secure small pieces to the base. Then use grozing pliers to trim off any glass spurs that detract from a smooth edge.

Optional Step: Top Layer of Glass

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Score and cut a top piece 1/8” larger then the base piece and place it on top of your completed glass design. This piece is usually a clear piece so that your design shows through after being fused or slumped.


Apply three even coats of AMACO Kiln Wash to kiln shelf. Allow each coat to dry.Place your “glass” piece on the kiln shelf inside the kiln. Close the lid and program the “Glass Select Fire” control for “Fuse” mode. Refer to the AMACO/Excel GSF-045 and GSF- 670 operating manuals, page 9, for Slow, Medium, or Fast settings. Or use the chart on page 2.

Slumping or "Slump" Method

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Follow the Fused Glass instructions to completion.

Then select a mold shape that you will set the “fused glass” on. This will be the shape or form your final warm glass piece will take.

Apply three even coats of AMACO Kiln Wash to the mold. Allow each coat to dry.

Place the mold inside the Glass Kiln and set the fused glass piece on top of the mold so that all sides are even with circumference of the shape.

Close the lid and program the “Glass Select Fire” control for “slump” mode. Refer to the AMACO/Excel GSF-045 and GSF-670 operating manuals, page 9, for Slow, Medium, or Fast settings. Or use the chart on page 2.


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Your finished piece may have rough edges and/or kiln wash stuck to the underside. Rinse the kiln wash off with water. For any edges that might appear too rough, use varying grades of sand paper to smooth down edges.


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