Lead Glass Manufacturing: Meeting Industry Standards

Historically, radiation glass manufacturing lagged behind other developments in radiation shielding. This was likely due to glass’ complex chemistry and difficulty of characterization.

However, with the rise of applications such as fiber optics, lasers, and photosensitivity, much research work is being done on the interaction of electromagnetic radiation and glass. Advanced glass products now protect people against the harmful effects of ionizing radiation wherever X-ray and gamma-ray technologies are in use.

Barrier Technologies® is proud to partner with Corning® Med-X® product range. Many imaginative glass materials and specialty applications originate from the brilliant scientists that work for this lead glass manufacturer.

Lead Glass Manufacturing Process

Did you know that glass is a phase of matter all of its own? It’s formed by heating a combination of solid oxides until they fuse. This vitreous mixture is cooled quickly to prevent it from crystallizing into a lattice structure. The result is that the molecules are locked into a disordered amorphous solid, somewhere between a solid and liquid.

Lead glass is manufactured much like ordinary glass. The only difference is that it’s impossible to temper (toughen) as it’s too soft, and has a much lower melting point. The process has six stages:

1. Melting and refining: The main ingredient is silica sand or silicon dioxide. This is mixed with lead oxide, barium, potash (potassium carbonate), and other compounds needed for stabilization and clarity. This mixture is melted in a furnace.
2. Floating: The molten mixture is poured onto a float bath of molten tin. The liquefied glass flows across the surface of the metal and forms a wide ribbon of consistent thickness. As it flows, it cools down and starts to harden.
3. Coating: Various coatings are applied to the surface of the glass to add reflective properties.
4. Annealing: The glass is conveyed through a special layered oven called a lehr, where each zone is cooler than the previous one. This releases any internal stresses and prevents spontaneous breakage.
5. Inspecting: Advanced inspection technology is used to identify imperfections such as air bubbles, stress cracks, or unmelted sand particles.
6. Cutting: The glass is cut into usable square sheets using diamond-edged cutters.

Lead Glass Properties

The addition of lead oxide to glass results in a product that has different properties to ordinary glass:

• Refractive Index: Lead glass has a refractive index of 1.7–1.8, while ordinary glass has a refractive index of 1.5. This greater light-bending ability is very useful for lens-making.
• Density: Ordinary glass has a density of 1.4 oz/cu in (2.4 g/cm3). High-lead glass is more than double this at 1.8–2.8 oz/cu in (3.1–4.8 g/cm3). Lead’s high atomic weight of 207.2 accounts for this large difference, making lead glass much heavier than ordinary glass.
• Viscosity: Lead glass is softer and more fluid. It can be manufactured and worked at lower temperatures than ordinary glass. Processing lead glass is easier, resulting in fewer trapped air bubbles and greater clarity.
• Attenuation: Lead in glass absorbs X-rays and gamma radiation, making it an excellent shielding material.

Lead Glass Composition

Optical, high lead glass has a very different composition from typical glass. It has a much lower silica content and contains no soda. It uses a simpler recipe with fewer ingredients. The typical glass used to make bottles and windows can contain six or more different oxides. Lead glass only contains three major ingredients.

The major constituents of radiation-protective lead glass by weight are 52% lead oxide (PbO) and 17% barium (Ba). The remainder is silicon dioxide (SiO2) and a negligible amount of potash or potassium oxide (K2O).

Corning Med-X glass contains the highest lead content in the industry and has a refractive index of 1.76. The percentage of visible light transmitted @ 550 nm through a 5 mm path is ≥85.0. This provides unrivaled optical clarity paired with 100% attenuation of harmful scatter radiation. Med-X glass won’t darken or yellow over time, ensuring that eyewear lenses are durable.

Standards and Requirements of Radiation Eye Protection

The National Institute for Occupational Safety and Health (NIOSH) sets the standards and requirements for radiation eye protection in 29 Code of Federal Regulations (CFR) 1910.132 and 133. To paraphrase the relevant information, protective equipment for eyes must be provided, used, and maintained in a sanitary and reliable condition wherever it is necessary because of radiological hazards encountered in a manner capable of causing injury or impairment.

Studies on radiation-induced cataractogenesis undertaken by the International Commission on Radiological Protection (ICRP) have resulted in a drastically reduced eye lens exposure limit. The proposal is that it should be lowered from 150 mSv to 20 mSv per year averaged over 5 years, or a maximum of 50 mSv in any given year.

Barrier Technologies uses Corning Med-X lead glass because:

• It is manufactured under strict controls according to Quality Standard ISO 9001, Environmental Standard ISO 14001, and Health & Safety Standard ISO 14045.
• It has the highest lead concentration, exceeding industry standards.
• It contains a large proportion of barium, which adds extra protection and improves the refractive index and luster.
• Its lenses offer at least 0.75mm lead equivalence, providing optimum shielding against radiation emitted by equipment operating in the 80–300 kV range.

Barrier Technologies: A Leading Lead Glass Industry Supplier

Barrier Technologies is a leading provider of leaded glass eyewear for radiation protection. We supply a wide range of stylish and practical designer lightweight frames fitted with the highest quality, most effective lead glass available. Our partnership with Corning Med-X glass manufacturing positions us as a single-source supplier for all your radiation shielding requirements.

We are dedicated to the research and development of advanced technologies that enhance the safety and comfort of all radiologic professionals. We can replicate your exact glasses prescription in leaded eyewear, using our sophisticated Digital Lens Surfacing System. You may also select our ClearView Anti-reflective and Anti-fog coatings for superior acuity.

Do you wear radiation PPE such as a lead apron and thyroid collar for your work? If so, don’t risk your precious eyesight! Choose our industry-leading eyewear to protect your sensitive eyes from the hazards of scatter radiation. Don’t delay—contact us today.