Low-Iron Glass vs Clear Float Glass: What's the Difference?
Low-iron glass is clear float glass made with most of the iron taken out. Standard clear glass contains iron oxide, and that is what gives it the familiar green edge tint. Low-iron keeps the iron content under roughly 0.01%, so the glass reads as neutral, close to water-white.
You will also see it sold as extra-clear or ultra-clear, and under brand names like Starphire and Optiwhite. They are all describing the same thing: a clearer base glass.
Where the green actually shows up
Standard clear float does not look green face-on. The tint shows up in three places:
- Edges. Look at the edge of a clear glass shelf and you will see it. It is most obvious on a polished edge, which is exactly the finish you want on a table top or a shelf where the edge is part of the design.
- Thickness. The tint grows with the amount of glass the light travels through. At 1/8" you barely notice it. At 3/8" and up it is hard to miss.
- Lighting. LED and fluorescent light make the green read stronger than daylight does, which is why it stands out so much in a retail display case.
Stack all three, a thick panel with a polished edge under LED light, and standard clear looks distinctly green. That is the case low-iron was made for.
When low-iron is worth the premium
- Display cases and retail fixtures. The green cast tints the merchandise. Low-iron lets the product color read true.
- Table tops and shelving. A polished edge puts the tint on display. See our glass table tops and shelving pages.
- Thick panels, 3/8" and above. The thicker the glass, the more the tint compounds.
- Glass markerboards. A whiteboard should read white. Standard clear reads pale green against white. See office furniture glass.
- Greenhouses. Low-iron transmits more visible light, which matters when light is the whole point.
- Frameless and butt-glazed work. With no frame to hide the edge, the edge is the finish.
When standard clear is the right call
Standard clear is not a downgrade. It is the right answer more often than not:
- Framed windows and doors, where the edge is covered by the frame or a stop.
- Any lite thin enough that the tint never registers.
- Work that sits against a dark background, which hides the green entirely.
- Insulated units, where the tint reads much less through the assembly than through a single thick lite.
- Budget-driven jobs where the difference will never be seen.
If you are not sure, tell us the application. We will tell you whether the upgrade is visible in your case.
What it costs
Low-iron is a premium glass. The adder is per square foot on the glass itself, and it becomes a smaller share of the finished part once cutting, edgework, and tempering are in the price. On a display case or a table top where the edge is in view, most customers decide it is worth it. On a framed window, most do not.
Tempering and edgework
Low-iron tempers like any other float glass and takes a polished edge the same way. One thing worth knowing: because there is no green tint to mask imperfections, tempering and edge quality show up more clearly on low-iron than on standard clear. That is usually a benefit. It also means the finish has to be right, which is work we do in house.
Availability and lead time
Clear, green, light gray, dark gray, bronze, and 3 mm obscure are usually on the rack. Low-iron is an ordered item, so it adds to the lead time. If your job needs it, tell us early and we will schedule the glass with the rest of the order. You can see what we keep in stock.
Frequently asked questions
Is low-iron glass the same as clear glass?
No. Both are clear float glass, but low-iron has most of the iron oxide removed, which is what eliminates the green edge tint. Standard clear glass still contains that iron.
Is low-iron glass stronger than regular glass?
No. Strength comes from tempering, not from the iron content. Low-iron and standard clear temper to the same strength. If you need strength, the answer is tempering.
Can low-iron glass be tempered?
Yes. Low-iron tempers like any other float glass, and it can be drilled, notched, and edged before it goes in the furnace just like standard clear.
Does low-iron glass cost more?
Yes. Low-iron carries a per-square-foot premium over standard clear float. The premium is on the glass itself, so it becomes a smaller share of the finished part once cutting, edgework, and tempering are added.
Is low-iron the same as Starphire or Optiwhite?
Those are brand names for low-iron glass. Starphire and Optiwhite are trade names from different manufacturers, but they describe the same low-iron, extra-clear material.