“I want coloured glass. I’ll just specify it from the supplier.”
You can — but the colour you get from a standard float glass catalogue is a limited set: standard greens, greys, and a few blues, all produced as body colour by adding metal oxides to the melt. If the colour matters to the design, you need to go further than catalogue selection. Body-coloured glass from a specialty melt gives you much more range — but requires minimum order quantities that don’t suit prototyping. The practical alternative for smaller quantities is laminated glass: a coloured interlayer (PVB or resin) bonded between two clear panels. The colour reads through the full thickness, and you can achieve gradients, patterns, and opacity levels that a single body-colour pour can’t.
”I want frosted glass.”
There are three different things called frosted glass, and they produce different results. Acid-etched glass produces a uniform, fine-grained surface that softens but doesn’t fully diffuse light. Sandblasted glass produces a coarser texture that diffuses more. Ceramic frit (a printed enamel layer fired into the surface) can produce any pattern, opacity level, or gradient — and can be combined with body colour. If the light behaviour of the glass matters to the design, specify which one you mean and why.
| Acid-etched | Sandblasted | Ceramic frit | |
|---|---|---|---|
| Surface | Uniform, fine, silky | Coarser, matte | Printed enamel, fired in |
| Light diffusion | Softens, low diffusion | Medium–high diffusion | Tunable, by pattern density |
| Patterns / gradients | Limited | Stencil-level | Full control |
| Fingerprints | Resistant (etched types vary) | Shows handling | Resistant |
| Combines with colour | Body colour only | Body colour only | Frit can be the colour |
”Glass can’t hold fine detail.”
Float glass can’t — the process produces flat sheets. Cast glass (poured into a mould and kiln-annealed) can hold significant three-dimensional form and surface texture, including hand-made qualities that the float process systematically removes. Cold-working — grinding, polishing, and cutting after annealing — can produce angles, edges, and surface treatments unavailable in any hot process. The combination of cast glass with cold-worked edges is where the material gets interesting for object and lighting design.
Where glass reliably fights you
Differential thermal expansion: wherever glass meets metal or ceramic, the joint needs to accommodate movement — a rigid glued joint between glass and brass will eventually crack the glass, not the brass. Tempered glass cannot be cut after tempering: all cutting, drilling, and grinding must happen before the toughening cycle, which means the drawing must be final before tempering starts. Batch colour matching across multiple production runs requires careful supplier management; glass colour varies with furnace conditions, so a piece reordered a year later may not match the first run without a new colour sample.
Annealing time scales with mass: a thick casting can spend days cooling. Rush a casting’s anneal and it carries internal stress that shows up later as a crack with no apparent cause.
Where it can be pushed
Dichroic glass — glass with a metallic oxide coating that transmits one colour and reflects another — produces the kind of colour shift that reads completely differently in different light conditions. Kiln-forming allows glass to slump into three-dimensional curves using a mould. UV-bonding can join glass to glass with no visible adhesive, producing structural forms that read as single pieces.
Cost drivers
- Process choice — float + cold-work is cheap; casting is mould + kiln time; specialty melts have real MOQs
- Annealing time — thick castings occupy a kiln for days, and kiln time is money
- Cold-working labour — every polished edge and ground face is hours, priced by hand
- Colour route — interlayer lamination prototypes cheaply; body colour does not
- Breakage and rejects — glass has a loss rate at every step; experienced workshops quote it honestly
What to put on the drawing
- The colour route: body colour, laminated interlayer, frit or coating — they are different supply chains
- Which “frosted” you mean: acid-etched, sandblasted or frit, with a sample reference
- Tempered or annealed — and remember nothing is cut after tempering
- Edge work: seamed, ground, polished, with the finish grade
- Joint design where glass meets other materials: gasket, bushing or flexible bond, never rigid
- Light source position for lighting pieces — the glass spec only makes sense against the light it carries