The iron content of ultra-clear glass is usually one order of magnitude lower than that of ordinary float glass, and the specific value is approximately 90% lower.
Ultra clear glass：Iron content (expressed as Fe₂O₃),Usually ≤ 150 ppm (0.015%) High-end products can be controlled below 100 ppm.
Iron content difference,standard. Reduce the percentage,standard. Glass color, Highly transparent, in the form of white glass or colorless. The main reason,Low-iron quartz sand and strict raw material control are used to reduce iron impurities from the source. Light transmittance,≥ 91.5% (6mm thick glass). Key impact,Iron is the main factor causing the coloring of glass. The lower the iron content, the less the glass absorbs visible light (especially the green light band), and thus it appears whiter and more transparent.
Ordinary float glass：Iron content (expressed as Fe₂O₃),It is approximately 1000 ppm (0.1%) or so (The range is usually between 0.08% and 0.12%). Iron content difference,It is approximately 850 ppm or more higher than ultra-clear glass. Reduce the percentage,The iron content is approximately 6 to 10 times that of ultra-clear glass. Glass color,The side or the cut is green. The main reason,The iron impurities in the raw materials (mainly from quartz sand and auxiliary materials) cannot be completely removed during the melting process. Light transmittance, Approximately 89% (6mm thick glass).
Supplementary explanations and impacts
The forms and colors of iron:
In glass, iron usually exists in the form of ferrous ions (Fe²⁺) and iron ions (Fe³⁺).
Ferrous ions (Fe²⁺) : They mainly absorb infrared rays and give glass a faint blue-green color.
Iron ions (Fe³⁺) : They mainly absorb ultraviolet rays and give glass a light yellowish-green color.
In ordinary float glass, both coexist, but the combined effect is the common green color we see. Ultra-clear glass greatly weakens this coloring effect through its extremely low iron content.
The direct result of performance differences:
Light transmittance: Due to its low iron content, ultra-clear glass has an extremely high visible light transmittance, which is 2-3 percentage points higher than that of ordinary float glass of the same thickness. This is crucial for fields with extremely high requirements for transparency, such as photovoltaic modules, high-end building curtain walls, museum display cases, furniture countertops, and aquariums.
Appearance: Ultra-clear glass has almost no green base color of ordinary glass. Visually, it is purer and more upscale, and can truly restore the original color of the object.
Cost variance
The production of ultra-clear glass requires carefully selected low-iron raw materials and stricter process control, which leads to its production cost being much higher than that of ordinary float glass. The price is usually 2 to 4 times or even higher than the latter.
Summary
The iron content of ultra-clear glass (≤0.015%) is approximately 0.085 percentage points lower than that of ordinary float glass (≈0.1%), which is reduced by about 90% proportionally. This seemingly minor numerical difference has brought about a huge leap in the transparency, color and quality of glass.
