Low-Iron Glass Explained: Why Optiwhite™ is the Clear Choice

When you look through a window, you assume you are seeing the world exactly as it is. When you install a glass splashback over a pure white wall, you expect it to look white.

However, standard glass is not actually “clear.” If you have ever noticed a distinct green tinge on the edge of a glass table or window pane, you have witnessed the inherent limitation of standard glazing.

For homeowners and architects seeking absolute clarity and true colour representation, the solution is Low-Iron Glass. In this guide, we explain why standard glass isn’t clear, and why premium products like Pilkington Optiwhite™ are the industry standard for high-end applications.

1. The Science: Why is Standard Glass Green?

All glass is made primarily from silica sand. However, the raw materials used in the standard “float glass” manufacturing process naturally contain impurities.

The culprit responsible for the green tint is Iron Oxide (Ferric Oxide). Even in trace amounts, iron oxide absorbs light at the red end of the spectrum and toward infrared, resulting in a greenish-blue hue that becomes more pronounced the thicker the glass gets.

2. The Solution: What is Low-Iron Glass?

Low-iron glass (often known as “extra-clear”) is manufactured using carefully selected raw materials with a very low iron content (approx. 0.02% vs 0.10%). This reduction removes the green cast, offering unparalleled light transmission and neutrality.

Visual Comparison: The “Edge Test”

The easiest way to spot the difference is to look at the exposed edge of the glass pane:

Left: Standard Float Glass (Green Edge). Right: Low-Iron Glass (Clear/Blue Edge).

3. Standard vs. Low-Iron Performance Data

The difference in clarity isn’t just subjective; it is measurable in Light Transmission (LT) values.

4. Pros & Cons (Trade-offs)

Is the upgrade worth the investment? Here is a balanced view.

5. Key Applications: When Clarity Matters Most

While low-iron glass is a premium product, it is essential in specific scenarios where the green tint of standard glass would ruin the aesthetic:

• Kitchen Splashbacks: If you paint the back of standard glass white or cream, the green tint will turn it mint green. Low-iron glass is mandatory for true whites and pastels.
• Retail Displays: Jewellers and museums use low-iron glass so products are displayed with perfect colour accuracy.
• Premium Architectural Glazing: For large picture windows framing a view, low-iron glass ensures the landscape is seen exactly as nature intended.
• Glass Balustrades: In frameless applications where the thick edges are visible, low-iron glass provides a much cleaner, modern aesthetic.

6. Compatibility with Other Tech

A common misconception is that you have to choose between clarity and performance. In reality, Low-Iron glass is just a “substrate” (a base material). It can be combined with almost any other technology:

• Low-E Coatings: You can apply a thermal coating to low-iron glass to create a high-performance, ultra-clear double-glazed unit.
• Laminated Safety: Low-iron glass can be laminated for security. This is especially popular for thick balustrades to avoid the dark green edge.
• Toughened Safety: It can be thermally toughened just like standard glass for use in doors and low-level windows.

7. Frequently Asked Questions