Specifying clear vs. low-iron glass for a Domlur frameless shower enclosure: the green-edge question under bright ensuite light

A 10mm frameless shower panel in a Domlur ensuite catches the 2 p.m. south-facing light and throws a visible green edge at the top joint line where the glass meets the brass spigot. The homeowner notices it before the architect does. Standard clear float glass—soda-lime, 3mm of silica and iron oxide—absorbs and re-emits in the green band. Low-iron glass (also called starphire or ultra-clear) costs 30–40% more per panel but reads optically neutral under the same light. The question is not whether the green edge exists. It does. The question is whether your spec, your site conditions, and your client's tolerance for it align.

Why clear glass reads green: the iron-oxide baseline

Float glass, the standard for frameless shower enclosures across Bangalore, contains iron oxide as part of its raw batch. At 1–2 mm thickness (a single lite), this iron content is invisible. At 8–12 mm (the structural thickness for a frameless panel), the cumulative path length through the glass body becomes visible as a pale green or blue-green cast, especially at the edge where light travels perpendicular to the surface rather than through the body.

This is not a defect. It is chemistry. The iron is there to stabilise the melt during manufacturing. Remove it, and you remove a cost efficiency that has made float glass the baseline for 40 years. But remove it, and you also remove the green.

In a Domlur ensuite with a south or west-facing window, the 2–4 p.m. direct sun hits the shower panel edge-on. The green becomes obvious. In a north-facing bathroom in Yelahanka or an interior ensuite in Whitefield, the green may not register at all because the light is diffuse and the edge is in shadow.

Site-condition checklist: when to specify low-iron

Orientation and window proximity

If the ensuite has a south or west-facing window within 2 metres of the shower panel, and that window is unobstructed, specify low-iron. If the window is north-facing or the room is interior, standard clear is defensible. If there is a deep overhang or a tree line that shadows the panel after 1 p.m., standard clear works.

Panel thickness and edge visibility

A 10mm panel shows more green than an 8mm one because the light path is longer. If your spec calls for 12mm (common for large unsupported spans in Indiranagar or Sarjapur Road), the green edge is unavoidable in bright light unless you specify low-iron. An 8mm panel in a small ensuite with a half-height enclosure may justify standard clear even in bright conditions.

Hardware finish and contrast

A brushed-brass spigot or hinge against a green edge reads warmer and can soften the contrast. A black powder-coat frame sharpens the green against the dark metal. If your spec includes black hardware on a frameless panel, the edge visibility increases. Low-iron becomes a stronger call.

Water quality and mineral buildup

Bangalore's Cauvery water carries a TDS of 200–300 ppm. Hard water deposits on the glass surface can obscure the green edge over 6–12 months. If the client is willing to accept mineral spotting as part of the material, standard clear may read acceptably after a year. If the spec includes regular descaling or a water-softening system, the glass stays transparent and the green stays visible—another reason to specify low-iron upfront.

Cost and specification language

Low-iron glass costs 30–40% more than standard float at the point of manufacture. For a 1.2 m × 2.0 m panel at 10 mm, the difference is roughly ₹8,000–₹12,000 depending on the fabricator and the hardware finish. This is material cost, not labour. The fitting time, the joint tolerance (±1 mm), and the site dimensions remain the same.

In your spec, write: "Shower enclosure glass: low-iron clear float, 10 mm, polished edges, all panels. No standard clear." Do not write "ultra-clear" or "premium clear"—these are marketing terms. Low-iron is the technical spec. If the budget does not stretch, specify standard clear and note in the RCP that the green edge is visible under south/west-facing light and is a characteristic of the material, not a defect.

Frameless shower panels in Bangalore are typically commissioned in low-iron clear when the ensuite is bright and the hardware finish is dark. Standard clear is specified when the room is interior-lit, the window is north-facing, or the budget is tight and the client accepts the green edge as a trade-off.

Commissioning and handover notes

If you specify low-iron, include it in the shop drawing callout and the site dimensions sheet. When the glass arrives on site, it will read noticeably more neutral than standard clear. The fabricator should confirm the low-iron specification on the delivery docket. If a panel arrives and reads green under the site light, it is standard clear, not low-iron—stop work and verify with the atelier before fitting.

At handover, brief the client on the material. If you specified low-iron, explain that the glass reads colourless because of the low iron content and the cost premium. If you specified standard clear, explain that the pale green edge is a characteristic of float glass at 10 mm thickness and is not a defect, and that it may become less visible over time as hard-water deposits accumulate (though regular cleaning will restore the transparency and the green).

Tinted glass and the green-edge trade-off

Some architects specify bronze or grey tint to mask the green edge. A bronze-tint frameless panel reads warmer and the green edge is absorbed into the overall tint. This works well in warm-lit ensuites in Koramangala or Sadashivanagar where the ensuite is already warm-toned. In a cool-lit space, bronze tint can feel heavy. Grey tint (not common in Bangalore frameless work) reads cooler but is a specification choice, not a solution to the green-edge question. If the brief is to read "crystal clear," tint is not an option. Low-iron is the only answer.

Questions we get asked

Does low-iron glass feel different to touch or clean differently than standard clear?

No. The iron content is in the bulk of the glass, not the surface. Cleaning, polishing, and joint tolerance are identical. Hard-water spotting and soap scum accumulate at the same rate. Low-iron simply reads optically neutral instead of green.

If I specify low-iron now, will it yellow or discolour over time?

No. Low-iron glass is stable. It will not yellow. The only change over time is mineral buildup from Bangalore's hard water, which affects both low-iron and standard clear equally. Regular cleaning restores the original clarity.

Can I upgrade to low-iron after the panel is fitted if the client complains about the green edge?

No. Once a frameless panel is fitted to the wall, the glass is fixed to the spigot and hinges with a joint tolerance of ±1 mm. Removing and replacing it risks damage to the fitting and the wall. Specify low-iron upfront if the site conditions warrant it.

Is low-iron glass stronger or more durable than standard clear?

No. Both are tempered to the same safety standard. The only difference is optical—the absence of iron oxide. Strength, impact resistance, and thermal shock tolerance are identical.

Does low-iron glass cost more to fit than standard clear?

No. Labour, site dimensions, and joint tolerance are the same. The cost difference is material only, absorbed at the point of manufacture and fabrication, not on site.

Specify the glass that matches your site light and your client's tolerance for a visible green edge. If the ensuite is bright and south-facing, and the hardware is dark, low-iron is the right call. Commission a fitting with the atelier and send the site dimensions and RCP details. We will confirm the glass specification on the shop drawing before fabrication begins.