Standard glass is green and you only see it sometimes. Where low-iron earns its cost — railings, showers, back-painted panels — and where it is money for nothing.
Standard clear glass is green. You do not see it in a window because the lite is thin and you look through it, not at it; you see it at the edge of a half-inch railing panel, in the reflection of a frameless shower against white tile, and through a back-painted kitchen panel that was supposed to be white and came out mint. Low-iron glass removes it. It costs more, and it is worth it wherever the glass is thick, the surroundings are pale, or a colour behind the glass has to read true. Everywhere else, standard clear is fine and the money goes elsewhere.
| Feature | Standard clear (float) | Low-iron (Starphire, Ultraclear) |
|---|---|---|
| Iron oxide in the batch | ~0.10% | ~0.01% |
| Colour | Faint green; strong at the edge and in thick lites | Neutral; edge is pale blue-white |
| Visible light transmission (6 mm) | ~89% | ~91% |
| Where the green shows | Edges of railings, showers, tabletops; back-painted panels; mirrors; anything against white | Nowhere |
| Cost | Baseline | Roughly 30–60% more for the glass itself |
| Availability | Every thickness and process | Most thicknesses; tempered, laminated, insulated; some antique-mirror patterns |
| When it matters | Thin lites in a dark room: barely | Thick glass, white surroundings, colour-critical finishes |
Float glass is made from sand, and sand carries iron. The iron oxide absorbs the red end of the spectrum, so what passes through is shifted green. The effect is proportional to the path length: through a 4-millimetre lite it is almost invisible; through the edge of a 12-millimetre panel — several inches of glass — it is bottle green. Low-iron glass is made from selected low-iron sand with the remaining iron chemically reduced; Starphire is Vitro’s brand, and Guardian, Saint-Gobain and AGC each have an equivalent.
Glass railings. The edges are on view, top and sides, and against a white building or black posts the green is the first thing an eye finds; the Ocean Parkway guards are low-iron for that reason. Frameless showers with white or pale tile, especially 1/2-inch glass; see 3/8 vs 1/2 inch. Back-painted glass in any pale colour: white, cream, grey. Mirrors where the reflection has to be colour-true, and the silver-leaning antique mirror patterns. Display and museum glazing. Curtain wall spandrels where the vision and spandrel glass must match.
A standard window in a normal room, where the lite is 4 to 6 millimetres and nobody looks at the edge. Dark tile, dark paint, dark stone behind the glass, where the green cast is swallowed. Tinted or reflective glass, where the tint is the point. Anywhere the budget is better spent on the coating or the hardware. Low-iron does nothing for strength, safety or insulation; it is purely optical, and it should be bought for an optical reason. See tempered vs laminated for the structural questions.
Starphire is Vitro’s brand of low-iron glass; Guardian UltraClear, Saint-Gobain Diamant and AGC Krystal are equivalents. All have the iron oxide reduced so the green cast is gone.
Typically 30 to 60 percent more for the glass itself; on an installed job the difference is smaller because labour and hardware are the same.
Yes, in the usual thicknesses. It is standard in frameless railings and showers and available in insulated units.
Slightly: about 91 percent visible transmission against 89 for standard clear at 6 mm. The difference you notice is colour, not brightness.
Usually not. The lite is thin and you look through it. Specify it where the glass is thick, the surroundings are white, or a colour behind it must read true.
Low-Iron vs Starphire Glass for Shower Doors Starphire Low-Iron Glass Glass Balcony Railings Frameless Shower Doors Back-Painted Glass All Comparisons
About this page. Written by Alex GC Inc. d/b/a Alex Glass Construction and reviewed before publication by Aleksandr Chernovolenko, Managing Partner, with our design and estimating lead and a field foreman. Our foremen hold the NYC DOB Site Safety Training supervisor card and our crews the 40-hour worker card; we are certified to fabricate, install and service Alutech and Everest aluminum systems. Facts are drawn from our own projects, manufacturer test data and the applicable codes; where we are giving an opinion, we say so. Last reviewed September 2026. Credentials
Tell us what the glass is for and what is behind it. We will say whether low-iron is worth it and quote both.
