Body Tinted Glass — Heat Absorbing Float

What it is

Float glass with metal oxide colourants added to the melt, giving bronze, grey, green, blue or black through the full thickness of the pane.

Because the colour is in the body, it cannot scratch, peel or wear.

Specification at a glance

Property	Typical specification
Standard	IS 14900 for float glass
Colours	Bronze, grey, green, blue, black
Thickness	5mm — 12mm common
Mechanism	Absorbs solar energy; does not reflect it
Heat treatment	Heat-strengthened advisable on sunny elevations
Combination	Frequently used as substrate for a coating

How tint behaves, honestly

Absorbed energy has to go somewhere. Roughly, a tinted pane re-radiates part of the absorbed heat inward and part outward, so the net solar reduction is far smaller than the drop in visible light suggests. A building can end up darker inside without being much cooler — which then increases artificial lighting load and works against the ECBC lighting power density target.

That trade-off is the reason tint alone is rarely the right answer in Indian conditions, and why spectrally selective coatings on a lightly tinted or clear substrate have largely replaced heavy tints on commercial work.

Where it still makes sense

Glare control on elevations where a view must be retained · architectural colour where a specific elevation tone is wanted · as a substrate beneath a solar control coating · secondary and back-of-house glazing where coated glass is not justified.

Where projects go wrong

• Dark tint in annealed glass on a sunny elevation — thermal stress cracks.
• Partial shading from a reveal or louvre across a tinted pane, which concentrates the stress at the shadow line.
• Relying on tint for an SHGC target.
• Mixing float batches, since tint colour varies subtly between runs and shows across a continuous elevation.

Standards referenced

Float glass specification under IS 14900. Fenestration SHGC under ECBC 2017. Architectural safety glass to IS 2553 (Part 1).