Photovoltaic glass sits on the front of every solar module, and its purpose is to transmit as much sunlight as possible to the cells beneath. Ordinary float glass transmits around 86% of light; PV glass needs 91.5% or more. The single biggest lever on that number is the iron content of the silica sand it's made from — which is why "low-iron" quartz is a distinct, premium product with a specification all its own.
Why solar glass is different
Most glass is judged on strength, clarity or colour. Solar glass is judged on transmittance — the percentage of incident light that passes through. Every fraction of a percent matters: across a utility-scale array of millions of panels, a small gain in transmittance translates into real additional generation over the system's life. That economic pressure is why PV glass makers chase the lowest achievable iron.
Iron: the enemy of transmittance
Iron oxide absorbs light in the visible and near-infrared range and gives glass a green cast — precisely what a solar panel cannot afford. Both ferric (Fe³⁺) and ferrous (Fe²⁺) iron reduce transmittance, with ferrous iron especially damaging in the infrared. Because the sand is 60–80% of the batch, its iron content is the dominant source of iron in the finished glass, so PV-grade sand is specified far more tightly than ordinary glass sand.
The PV-grade specification
Industry standards for photovoltaic silica are demanding:
- Fe₂O₃ — typically capped at 100 ppm, with many producers controlling below 50 ppm.
- SiO₂ — generally 99.5–99.7% or higher.
- TiO₂ — limited, since titanium yellows glass and blocks light.
- Al₂O₃, CaO and alkalis — kept low to protect melting behaviour and prevent devitrification.
The finished ultra-white glass itself often targets an iron level around 100–150 ppm, which is only achievable with sand at the low end of the range. For the full spec picture across all glass types, see our silica sand specifications for glass manufacturing.
Ultra-clear glass and transmittance
"Low-iron", "ultra-clear" and "extra-white" describe the same broad family: glass engineered for maximum clarity and light transmission. Where ordinary float glass transmits around 86%, ultra-clear PV glass exceeds 91.5% and high-end products push higher still. That difference is delivered almost entirely by controlling iron in the raw materials.
Getting the iron out
Low-iron sand is manufactured, not just dug up. Producers combine several beneficiation steps: washing and mechanical scrubbing to remove surface iron and clay, magnetic separation (often high-intensity) to pull out magnetite and ilmenite, and flotation and acid leaching to strip the last stubborn iron for the highest grades. The number and intensity of these steps is what separates true PV-grade sand from ordinary silica — and it's the main reason low-iron quartz commands a premium.
Beyond solar
The same ultra-low-iron quartz feeds other high-clarity markets: extra-white architectural glass and façades, furniture and display glass, greenhouse glazing, high-end tableware, and optical applications — anywhere brilliance and light transmission are the selling point.
Sourcing low-iron quartz
When you buy, three things separate a reliable supply from a risky one:
- Iron reported in ppm, not percent — a "%"-only figure is too coarse for PV work.
- A clear beneficiation description — confirm washing, magnetic separation and, for the lowest grades, flotation/leaching.
- Batch consistency — a single high-iron lot can compromise an entire production run, so consistency matters as much as the headline number.
Our high-purity Premium Quartz Sand is graded for demanding glass applications with a COA on every consignment. Tell us your target iron (in ppm) and volume and we'll come back with a quotation.
Frequently asked questions
Why does solar glass need low-iron sand?
What is the iron limit for PV-grade quartz?
What SiO₂ purity does solar glass sand need?
How is iron removed from quartz sand?
Is low-iron quartz used for anything besides solar?
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