Glass glossary: Indian trade terms explained
The Indian glass trade mixes technical English, brand names and Hinglish — patti, pinhead, DGU, spider fitting. This glossary defines 37 terms you will hear at a glass shop or on a site, in one or two plain sentences each. For deeper detail, see our glass thickness guide, types of glass compared and standard sheet sizes.
All terms, A to Z
Annealed glass
Ordinary float glass cooled slowly at the factory, with no extra strengthening. It is the cheapest form of glass but breaks into large, sharp shards, so it is unsafe for doors, partitions and anywhere people can walk into it.
Argon fill
Argon gas sealed inside the cavity of a double-glazed unit in place of air. Being denser than air, it slows heat transfer and improves the unit’s insulation by roughly 5–10%.
Back-painted glass
Glass with opaque paint applied to its rear face so the front shows a uniform colour with a glossy finish. Widely used for kitchen backsplashes, wall cladding and writing boards; the term overlaps with factory-made lacquered glass.
Bevelling
Grinding the edge of glass or mirror at an angle, typically 10–40 mm wide, to create a sloped, decorative border. Common on mirrors and table tops; priced per running foot in the Indian trade.
BIS mark
The Bureau of Indian Standards certification mark stamped on safety glass, indicating conformity to standards such as IS 2553 for toughened and laminated glass. Builders and architects increasingly insist on BIS-marked glass for doors, facades and railings.
Copper-free mirror
A mirror made without the traditional copper layer behind the silver coating, using protective paints instead. It resists edge corrosion (black spots) far better in humid Indian bathrooms and is now the default from brands like Saint-Gobain and AIS.
Cutouts and holes
Openings drilled or cut in a glass panel for locks, handles, sockets, spider fittings or basin fixtures. They must be made before toughening — toughened glass cannot be drilled afterwards — and each hole or cutout is charged separately.
Demister
A thin electric heating pad fixed behind a bathroom mirror to keep it fog-free after hot showers. Sold as an add-on with premium mirror installations in India.
DGU (double-glazed unit)
Two glass panes factory-sealed with a spacer and an air or argon gap between them, also called an insulated glass unit (IGU). DGUs cut heat gain and outside noise, which is why they dominate facade glazing and premium windows in India.
Edge polishing (flat / pencil / OG)
Finishing the cut edge of glass so it is smooth and safe to touch. Flat polish gives a squared shiny edge, pencil (round) polish gives a curved edge, and OG is a decorative double-curve profile — each priced per running foot.
Figured glass
Glass with a decorative pattern rolled into one face during manufacture, making it translucent but not transparent. Indian shops stock patterns like karachi, bajri and flora for bathroom windows and partitions where privacy is needed.
Float glass
The standard flat glass of the modern industry, made by floating molten glass over a bath of molten tin to get perfectly flat, distortion-free surfaces. Nearly all clear glass sold in India — by Saint-Gobain, AIS, Gold Plus and others — is float glass.
Frosting / etching
Treating a glass surface with acid or abrasives so it turns milky-translucent for privacy. Acid-etched glass has a smooth, uniform finish; the terms are used loosely in the trade for any non-film matte finish.
Heat-soak test
An oven test in which toughened glass is held at about 290°C for a couple of hours to force panels containing nickel-sulphide impurities to shatter at the factory instead of on the building. Specified for facades and balustrades to reduce spontaneous breakage on site.
Heat-strengthened glass
Glass heat-treated to about twice the strength of annealed glass — less than toughened — with much lower risk of spontaneous breakage. It breaks in large pieces, so it is used in laminated facade panels rather than alone as safety glass.
IGU spacer
The aluminium or warm-edge bar that separates the two panes of a double-glazed unit and sets the gap width, usually 6–16 mm. It contains desiccant to keep the sealed cavity dry so the unit does not fog internally.
Jumbo sheet
The full-size sheet a float line produces, typically 3210 × 6000 mm. Jumbos move only between plants, processors and large distributors, who cut them into the stock sizes dealers sell.
Lacquered glass
Glass with a factory-baked opaque lacquer on the back face, giving a durable, uniform colour — the branded version of back-painted glass. Used for wardrobe shutters, wall panels and kitchen dados.
Laminated glass
Two or more glass layers bonded with a plastic interlayer (usually PVB) so the panel holds together when it breaks. It is the safety choice for overhead glazing, floors, railings and burglar-resistant shopfronts.
Low-E glass
Glass with a microscopically thin low-emissivity metallic coating that reflects heat while letting light through. In Indian conditions it mainly cuts solar heat gain, lowering air-conditioning load in glazed buildings.
Low-iron glass
Extra-clear glass made with reduced iron content, removing the greenish tint visible on the edge of ordinary clear glass. Sold under names like Saint-Gobain Diamant; preferred for display cases, back-painted panels and premium partitions.
Nesting / optimization
Arranging multiple cut sizes on a stock sheet — by software or an experienced cutter — to minimise wastage. Good nesting is why ordering several pieces together is often cheaper per square foot than ordering one.
Patch fitting
A small stainless-steel or aluminium clamp that fixes a frameless toughened-glass door to the floor, top pivot or an adjacent panel through cutouts in the glass. A standard frameless office door uses a set of four patches plus a floor spring.
Patti
The Hindi trade word for the beading strip — wood, aluminium or PVC — that holds a glass pane inside a frame. When a glazier says the patti must be opened, they mean removing the beading to take the glass out.
Pinhead glass
A figured glass with a fine dotted (pinhead) texture on one face, giving privacy with good light transmission. A long-standing favourite for bathroom windows and office cabin partitions in India.
PVB interlayer
Polyvinyl butyral, the standard plastic film laminated between glass layers, commonly 0.38 or 0.76 mm thick. It holds broken glass together and blocks over 95% of UV light.
Safety film
A transparent polyester film stuck onto existing glass so shards stay held together if the pane breaks. A retrofit alternative where replacing annealed glass with toughened or laminated glass is not practical.
Sandblasting
Blasting a glass surface with abrasive grit to make it frosted, either fully or through stencils for logos and patterns. Cheaper than acid etching but slightly rougher, so it marks with fingerprints unless sealed.
SGP interlayer
SentryGlas Plus, a stiff ionoplast interlayer several times stronger and stiffer than PVB. Specified for glass floors, canopies and frameless railings where the laminate must carry load even after breakage.
Spider fitting
A four-arm (or two-arm) stainless-steel bracket that bolts glass facade panels to a supporting structure through drilled holes. Spider glazing gives the frameless look on shopfronts and office facades, normally in 12 mm toughened glass.
Spigot
A short floor- or side-mounted clamp, usually stainless steel, that grips the bottom edge of a glass railing panel without a continuous frame. A typical balcony railing uses two spigots per panel of 12 mm toughened glass.
Standoff
A bolt-like fixing that holds a glass panel a fixed distance off a wall or staircase stringer through a drilled hole. Standoff-fixed glass railings give a floating look and need laminated or toughened glass with precise hole positions.
Structural glazing
A facade system where glass is bonded to the building frame with structural silicone so no metal caps show on the outside. Ordinary weather silicone only seals joints against water — it must never be used to carry the glass’s load.
Tinted glass
Glass coloured in the melt — grey, bronze, green or blue in India — to cut glare and solar heat. Unlike films or coatings, the colour runs through the body of the glass and cannot peel.
Tolerance
The permitted deviation between the ordered size and the delivered glass, typically ±1–2 mm on cut sizes in the Indian trade. Frameless work and DGUs need tighter tolerances, so confirm them in writing for critical fits.
Toughened glass
Glass heated to about 620°C and quenched rapidly, making it four to five times stronger than annealed glass; it breaks into small, blunt granules. Also called tempered glass, it cannot be cut or drilled after toughening.
U-channel
An aluminium or stainless-steel channel, commonly 12–25 mm deep, into which the edge of a frameless glass panel sits. Used at the floor and ceiling of glass partitions as a cheaper alternative to spigots or patch fittings.
Know the terms — now get the glass
Tell us the size and type — we'll connect you with verified glass suppliers near you for a free, no-obligation quote.
Request a free quotation →Also see: types of glass compared, standard sheet sizes, all glass tools.