Resources
Glass Glossary.
A plain-language guide to the glass terms we use every day — what the products are, how they are made, and what the numbers mean.
A
- Absorptance
- The share of sunlight and heat a pane soaks up rather than transmitting or reflecting; absorbed energy is later re-radiated both inwards and outwards.
- Acoustic laminate
- Laminated glass with a sound-dampening interlayer that noticeably reduces noise passing through a pane.
- Annealed glass
- Ordinary float glass allowed to cool slowly, leaving low internal stress. It cuts easily, but breaks into large, sharp shards.
- Annealing lehr
- The controlled-cooling oven on a float glass line that relieves internal stress so fresh glass can be cut and processed safely.
- Argon gas
- A clear, inert gas used to fill the cavity in double glazing, because it insulates better than air.
- Arrised edge
- A glass edge whose sharp corners have been ground off for safe handling.
- Aspect ratio
- The relationship between a panel's long and short side, which affects how it carries wind load and how far it can deflect.
- Autoclave
- A high-pressure, high-heat vessel that bonds glass and interlayer together into laminated glass.
B
- Balustrade
- A framed or frameless glass barrier protecting a change in floor level, typically one metre or more.
- Bevelling
- Grinding and polishing a sloped edge onto glass — most often on mirrors — for a decorative finish.
- Bent glass
- Flat glass reheated and curved to shape over a mould.
- Glazing bead
- The strip of timber, uPVC or metal that holds the glass in place within a frame's rebate.
- Bite
- The depth to which the glass overlaps, or is gripped by, the frame or structural silicone in glazing.
- Body-tinted glass
- Glass coloured throughout by metal oxides added to the molten batch, reducing solar transmission and glare.
- Break pattern
- The way a pane cracks when broken: toughened glass dices into small blunt fragments, annealed glass into large sharp shards.
C
- Cavity
- The sealed air or gas space between the panes of an insulating glass unit.
- Condensation
- Moisture forming on a cold surface when humid air meets it. On the outer face of efficient double glazing, it is actually a sign of good insulation.
- Coating
- A microscopically thin metallic or ceramic layer applied to glass to change its solar or thermal performance.
- Conduction
- Heat transferred directly through the materials of the glass and its frame.
- Curtain walling
- A non-loadbearing outer skin of glass and framing hung on a building's structure, often spanning several floors.
D
- Desiccant
- The moisture-absorbing material inside a spacer bar that keeps a unit's cavity dry and fog-free.
- Diffuse reflection
- Light scattered in many directions off a textured or frosted surface, giving privacy without blocking light.
- Double glazing
- Two panes assembled into one sealed unit with a spacer and cavity, for thermal and acoustic insulation.
E
- Edge work
- The ground, polished or bevelled finishing applied to cut glass edges.
- Edge deletion
- Removing a strip of coating along a pane's edge so the sealant can bond directly to the glass.
- Emissivity
- How readily a surface radiates absorbed heat. Low-emissivity (Low-E) coatings keep radiant heat on the side of the glass it belongs to.
- Etched glass
- Glass whose surface has been permanently frosted by acid or sandblasting.
F
- Float glass
- The standard flat glass, made by floating molten glass on a bath of molten tin to give a uniform, fire-polished surface.
- Frosted glass
- Glass with an acid-etched or sandblasted surface that transmits light but blurs vision.
- Frit
- Ceramic enamel fused onto glass, used for patterns, solar shading and to conceal fixings.
G
- Gasket
- A rubber or silicone strip that cushions and seals the glass against its frame.
- Glazing
- The glass itself, and the work of fitting it into frames.
- Glazing rebate
- The recess in a frame that receives the glass, its bedding and the beads that hold it.
H
- Hard coat
- A pyrolytic Low-E coating fused into the glass while it is still hot; durable enough to survive bending and handling.
- Heat soak test
- Holding toughened glass hot so that suspect inclusions break it on the bench rather than in the building — a screening step against spontaneous breakage.
- Heat-strengthened glass
- Glass cooled under controlled stress to roughly twice the strength of annealed glass; it still breaks like annealed glass but resists thermal stress far better.
I
- Insulating glass unit (IGU)
- Two or more panes separated by a spacer and sealed into a single unit, often gas-filled, for insulation and sound control.
- Interlayer
- The plastic sheet — usually PVB — bonded between panes to make laminated glass. It holds the shards together if the glass breaks.
K
- Kiln-formed glass
- Glass slumped or fused in a kiln into textured or shaped decorative panels.
L
- Laminated glass
- Two or more panes bonded with an interlayer. On impact it cracks but stays in the frame — which is why it counts as safety glass.
- Light transmission
- The percentage of visible light that passes through the glass.
- Low-E glass
- Glass with a low-emissivity coating that reflects radiant heat while letting light through, improving comfort in both summer and winter.
M
- Mirror glass
- Glass with a reflective metallic coating applied to its back face.
- Monolithic glass
- A single pane of glass, as opposed to a laminated or insulating unit.
O
- Obscure glass
- Patterned or textured glass that lets light through while blurring vision — common in bathrooms and entrance doors.
P
- Pane
- A single sheet of glass cut to size.
- Partitioning
- Internal glass screens that divide space while preserving light — framed or frameless, and double glazed where privacy is needed.
- PVB
- Polyvinyl butyral, the standard interlayer in laminated glass.
- Pyrolytic coating
- A coating fused into the glass surface during manufacture, making it extremely durable.
Q
- Quenching
- The rapid, controlled air-cooling that puts toughened glass into compression — the source of both its strength and its safe break pattern.
R
- Rebate
- The recessed ledge in a frame that the glass sits in.
- Reflective glass
- Glass with a metallic coating that bounces a significant share of solar radiation away, reducing heat and glare.
S
- Safety glass
- Glass that is unlikely to cause serious cuts when broken (toughened) or stays in place (laminated). Required in doors, low-level glazing and balustrades.
- Sandblasting
- Blasting the glass surface with abrasive to frost it permanently; masks can create patterns or logos.
- Sealed unit
- Another name for an insulating glass unit.
- Shading coefficient
- The proportion of solar heat a glass admits compared with clear glass of the same thickness.
- Silk-screened glass
- Glass printed with ceramic ink and heat-fused into the surface, used for patterns and shading.
- Silicone sealant
- Structural or weather-sealing silicone used to bond glass to frames, including in frameless structural glazing.
- Solar heat gain coefficient
- The fraction of the sun's energy that passes through the glass, both directly and as re-radiated heat.
- Spacer bar
- The profile that keeps the panes of an insulating unit apart and holds the desiccant.
- Structural glazing
- Glass bonded to the building structure with structural silicone or clamped fittings, so the facade reads as frameless glass.
T
- Thermal break
- An insulating barrier within a frame profile that slows heat conducting through it.
- Tinted glass
- See body-tinted glass — glass coloured in the molten batch to reduce solar transmission and glare.
- Toughened (tempered) glass
- Glass heated and then rapidly quenched so its surfaces are in compression — about four to five times stronger than annealed glass, and it breaks into small blunt fragments.
- Transmittance
- The share of light or energy that passes through the glass.
U
- U-value
- A measure of how well glazing conducts heat. The lower the number, the better the insulation.
- UV transmission
- How much ultraviolet light passes through. Laminated glass blocks most of it, protecting interiors from fading.
V
- V-groove
- A decorative V-shaped cut ground into a glass or panel surface.
- Veneer
- A thin slice of fine timber or laminate applied to panel and door surfaces, giving the look of solid timber.
- Visible light transmission (VLT)
- The percentage of visible light a glass lets through.
W
- Warm-edge spacer
- A spacer made of low-conductivity material rather than metal, reducing heat loss around the edge of an insulating unit.
- Wired glass
- Glass with a steel mesh embedded in it, holding fragments in place in fire-rated glazing.