Safety first!

Tempered glass is produced by treating annealed glass to cause the surface to compress while simultaneously putting the center of the glass in tension. This can be done with heat or chemicals. The glass must break in a manner that reduces the likelihood of cutting and piercing injuries to humans when breakage occurs from impact. Tempered glass tends to require significant blunt force or a concentrated point type impact to break. Once the surface compression layer is penetrated, the glass will shatter.

For heat-tempered glass, breakage tends to result in a loud pop as the energy is released, with the glass vacating the opening and glass particles spraying a good distance from the origin creating falling or flying “cubes” or “patches” of glass. There are requirements for the maximum size of the glass “cubes” as determined by the number of pieces within a specified area.

Tempered glass offers approximately four times more glass strength than annealed glass. Because of this, it is often used as a mechanism for thinner glass or larger panels of glass under a specific load. Tempered glass made via heat-treatment method may exhibit optical properties such as roller waves and anisotropy. Heat-tempered glass is commonly found in storefronts, facades, and the side and back glass of some cars.

Chemically tempered safety glass uses the same principles, but the glass is strengthened through a chemical exchange at the surface. This type of glass tends to be thinner, such as the glass on your cell phone. But technology is advancing to allow thicker and larger glass to be made in this manner. Chemically tempered safety glass is subjected to the same glass breakage size requirements as heat-tempered safety glass. Usually, the technology used for chemically strengthened glass does not produce roller waves.

Tempered glass has the same properties as annealed glass for solar, thermal, color and acoustic.

Laminated glass is an assembly of glass and Saflex® or Vanceva® PVB interlayers. The glass can be annealed, heat-strengthened, fully tempered, chemically strengthened, patterned, coated, fritted, etc. Two or more pieces of glass are bonded with an interlayer to bring valuable properties to the laminated unit.

For safety glazing, the interlayer provides resistance to impact penetration. Once the glass breaks from the initial impact, the interlayer allows the energy of the impact to be absorbed as it stretches along the cracks and fissures, causing the telltale spider-web break pattern. The interlayer acts as a solid elastic web, expanding, thinning, and intentionally allowing for micro-delamination to help prevent penetration while, at the same time, tenaciously hanging onto the glass shards to help prevent pieces of glass from flying or falling off the laminated glass unit.   Some of the safety glazing standards even have limits on how much glass can be released from the laminated unit on impact and still qualify as safety glazing.

All safety glazing standards require that, after impact, no opening be created in the laminated unit through which a solid steel ball the size of a tennis ball could fit through without a lot of force. This means that the laminated unit cannot vacate the opening and is the reason laminated glass is the required product for overhead or sloped glazing in many parts of the world.

For most applications, laminated glass with conventional Saflex Clear PVB interlayer is deemed to have glass strength similar to the equivalent nominal thickness of total glass used to construct the laminate. In addition to the ability of the interlayer to hold onto the broken glass shards, laminated glass can also bring other valuable performance attributes such as security, sound abatement, solar control, color, reduction of fading, and storm protection. Using Saflex Structural (DG) interlayer may also offer enhanced structural capabilities.