Glass — Material Overview

What It Is

Glass is an amorphous solid made primarily from silica (SiO₂) — the same silicon dioxide found in quartz sand. The addition of soda ash (Na₂CO₃) lowers the melting point; lime (CaO) provides stability. The result — soda-lime glass — is the most common glass worldwide. Borosilicate glass (Pyrex) adds boron trioxide (B₂O₃), raising the thermal shock resistance dramatically and creating a material that withstands much more extreme temperature changes.

Unlike crystalline solids, glass has no defined melting point — it transitions gradually from rigid to viscous as temperature rises. This property is fundamental to glass art: the material can be formed, pulled, blown, cast, and fused across a wide temperature range.

Glass-Making Approaches

Hot Shop / Glassblowing

Working with molten glass (approximately 1040–1200°C) on a blowpipe or punty. Glass is gathered from a furnace, shaped through blowing, marvering (rolling on a flat steel surface), and tooling. The material must be reheated constantly — it stiffens quickly below 1000°C. Glassblowing requires an annealer (a slow-cooling oven) to relieve internal stress after shaping.

Training: Berlin Glass (Berlin); UrbanGlass (Brooklyn, New York)

Kiln Casting

Casting glass into a mould using kiln heat, from approximately 800°C (fusing flat layers) to 1120°C+ (full flowing cast). Moulds are typically made from a 50:50 plaster/silica mix. The lost-wax process uses wax to make the positive shape, which is burned out in the kiln before glass is cast in. After casting, glass must be annealed — slowly cooled through the stress-relief zone (approximately 482–515°C depending on glass type) to prevent cracking. Thick pieces require days or weeks of annealing.

Flamework / Lampwork

Shaping glass rods and tubes using a bench torch. Two main glass types: COE 33 (borosilicate, high-strain-point glass requiring very high flame temperature) and COE 104 (soft/soda-lime glass, lower temperature, easier for bead making). These two types are incompatible — mixing them causes stress fractures as they cool at different rates. See: Flamework & Borosilicate.

Training: Berlin Flame Studio (Berlin)

Glass as Surface — Alternative Photography

Glass as a photographic substrate is covered in detail in Cyanotype on Glass. Key note: agar is the correct coating agent for cyanotype on glass; gelatin fails due to the iron chemistry's humidity sensitivity.

Other glass surface applications explored at Material Memory Studio:

• Liquid emulsion (silver gelatin) poured onto glass — creates a semi-opaque photographic surface on any solid material
• Anthotype on glass — plant-pigment photographic process (see: Anthotype)
• Cliché verre — drawing on glass coated with opaque material, then using as a photographic negative

Glass in Context — Material Memory

Glass holds light and transmits it. Unlike paper or fabric, which absorb and reflect, glass passes light through — changing its quality rather than stopping it. This transmission property connects glass to the themes of transparency, memory, and the preservation of image that run through Material Memory Studio's practice.

In installation, glass fragments found on streets (Berlin, New York) have been embedded with organic materials — testing the meeting point between geological permanence and biological fragility.

Related Entries

Flamework & Borosilicate · Kiln Casting · Cyanotype on Glass

References

• Berlin Glass, Berlin — hot shop and kiln casting
• Berlin Flame Studio, Berlin — flamework/borosilicate
• UrbanGlass, Brooklyn, New York — hot shop, jewellery, advanced techniques