Frequently Asked Questions

Glass that is used for more than just a functional purpose—particularly if it is designed to be pretty or change the look of the space in which it is used—is decorative glass (also known as ornamental glass).

The use of decorative glass can range from frosted, colored or textured glass doors (especially shower doors) to stairways, hand rails, kitchen backsplashes, tables and walls. Furniture made of glass is classified as decorative glass, as are shelves and structural glass floors.

Various options exist for different colors, transparencies, surface structures, reflectivity and opacity levels are available. Ranging from clear and colored float glass, mirrors, painted glass, up to and including glass with a satin touch or optical features.

Monolithic glass consists of a single sheet of architectural glass and comes in various thickness and sizes. The term does not apply to laminated glass.

Float glass is the initial product resulting from “floating” a ribbon of molten glass over a pool of liquid tin. Glass is floated to create annealed monolithic glass that is nearly defect free, with a uniform thickness, and with a very smooth surface finish. Depending on the raw materials melted down in the process, float glass is clear (with a greenish hue you can see on the edges), low-iron (no color and nearly white), or tinted such as blue or dark green. The quality standards for float glass are defined by ASTM C 1036 – Standard Specification for Flat Glass.

Traditional float glass consists of silica sand, soda ash, limestone, dolomite, and recycled cullet glass. The silica sand used has about 0.10% ferric oxide (iron content) which gives float glass its greenish tint. When looking through normal float glass, such as in residential or commercial windows, it is very difficult to see the greenish tint. However if you look at the edge of traditional float glass, it is easier to see the green tint.

Low-iron glass is near-colorless and is also referred to as “optically-clear” glass. As the name suggests, low-iron glass has ten times less iron content than traditional float glass. Low-iron glass is excellent for back-painted, color-laminated glass applications, display cases, shelving, decorative applications when exposed edges are visible because it renders the truest colors.

Low-iron glass can be treated the same way as clear float glass, being tempered during manufacturing or laminated afterward.

Annealed glass is glass that is slowly cooled during the manufacturing process to prevent residual stresses from forming, allowing it to be easily handled and processed for cutting, grinding, drilling and other fabrication steps. When broken, annealed glass will break into large pieces, often with very sharp edges and can cause significant injury to people or damage to property nearby.

Annealed glass is not as strong as tempered or heat-strengthened glass of the same thickness. Annealed glass is not safety glass.

Heat-strengthened glass is intended for general glazing, where additional strength is desired. It is approximately two times stronger than regular annealed glass of the same thickness. It features a surface compression between 3,500 and 7,500 psi and an edge compression of 5,500 psi or greater. Heat-strengthened glass break pattern is like annealed glass. Heat-strengthened glass is not safety glass.

Tempered glass is cooled very quickly during the manufacturing process to increase the strength of the glass. By cooling hot glass rapidly in a process called quenching, tempered glass has very high internal stresses – making it stronger than annealed glass. The surface of tempered glass is approximately four times stronger than the surface of regular annealed glass of the same thickness.

In addition to being stronger than annealed glass, tempered glass shatters into small pieces when broken, instead of large shards like annealed glass. Tempered glass is the opposite of annealed glass. Tempered glass is safety glass if it meets:

• Requirements for ANSI Z97.1 and/or CPSC 16 CFR 1201 and is typically labeled with a “safety” logo identifying the fabricator, glass type, and the standard it meets.
• The Safety Glazing Certification Council (SGCC) is the largest independent third-party that inspects and test tempered glass to confirm the manufacturing process and result. The SGCC is a voluntary organization. Glass manufacturers/fabricators that pass SGCC requirements are able to etch the SGCC logo permanently onto the glass, as notification that the glass has been properly produced.

Tempered glass is required as safety glazing in “hazardous” applications, such as floor-to-ceiling partition walls, entrance doors, sidelites, etc.

Tempered glass cannot be further processed (i.e., cut, drilled, notched) but can be back painted and/or laminated with other glass. Tempered glass is also referred to as “toughened” or “fully tempered” glass.

Safety glass is tempered glass (also referred to as “toughened” or “fully tempered” glass) and/or laminated glass that meets the requirements for ANSI Z97.1 and the federal safety standard CPSC 16 CFR Part 1201 (Consumer Product Safety Commission Safety Standard for Architectural Glazing Materials).

Glass is a breakable material. If it breaks into sharp pieces, or shards, it can injure people and pets. Safety glass improves occupant safety and well-being by significantly reducing this risk. In the case of tempered glass, if broken, it exhibits a characteristic “dice” break pattern of many small pieces that minimize the risk of injury. In the case of laminated glass, if broken, it remains in place, held together by the plastic or resin interlayer at its core.

The Consumer Products Safety Commission establishes the federal standards and requirements for safety architectural glass. Federal safety glazing law requires the use of safety glass in defined hazardous locations, designated by the Model Building Codes. Generally, these include:

• Bath and shower enclosures
• All doors, including storm doors, sliding doors, and combination doors
• Sidelites, including and any glazing next to a door or an opening for human passage, if the nearest exposed edge is within 24” (0.6 m) of the vertical edge of the door or the bottom exposed edge is less than 60” (1.5 m) above the walking surface
• Areas where the glass is adjacent to walking surfaces and the bottom edge of the glass is within 18” of the floor
• Areas where the top edge of the glass is more than 36” above the floor
• Glazed panels greater than 9 ft.2 (0.8 m2)

Local building code authorities may have additional safety glazing requirements, which can vary by state, county, city, town, or borough. Because each state has either adopted the model federal safety building code, modified it in some sections, or written completely new sections, it is imperative to be guided by the particular state or local building code where the glass is to be installed. For detailed information, please contact your local code officials.

Toughened glass is another name for tempered glass. See Tempered Glass for more info.

Laminated glass contains at least two pieces of glass and one plastic interlayer (PVB, EVA, or an ionoplast polymer), though it can be made with more layers if needed.

Laminated glass can be made up with annealed glass, heat-strengthened glass, tempered glass or a combination of these. When laminated glass breaks, the pieces remain attached to the film, preventing the glass from flying or falling and causing injuries or damage. Additional benefits of laminated glass include improved UV and sound control. Various decorative features can be incorporated into laminated glass, including virtually unlimited custom color, textured pattern glass, and interlayer options, are also available.

Laminated glass is safety glass when it meets the requirements for ANSI Z97.1 and/or CPSC 16 CFR 1201 and is typically labeled with a “safety” logo identifying the fabricator, glass type, and the standard it meets.

Laminated tempered glass combines two pieces of tempered glass with a plastic interlayer to create a sandwiched construction. When broken, the tempered glass will shatter into very small pieces and are held together by the plastic interlayer. The lamination reduces the possibility of loose, tiny glass shards from flying around. Laminated tempered glass is used in glass railings, skylights, overhead canopies, and glass stairs.

The term “heat treated glass” refers to tempered (safety) glass and/or heat-strengthened (non-safety) glass.

As the name suggests, back-painted glass is glass that has been painted on the back side. Back-painted glass can be tempered or laminated. Commercial back painted glass utilizes special water-based paints in a controlled clean room environment with special paint guns. In addition, commercial back painted glass has a durable, protective paint layer over the colored layer to not only protect the colored layer, but also to provide a durable surface that adhesive can durably stick to when mounted to horizontal or vertical surfaces. Back painted glass applications include wall cladding, elevator interiors, backsplashes, and counter tops.

The interlayer is the plastic used in between pieces of glass to make laminated glass. Common interlayer material is polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), and an ionoplast polymer such as Sentryglas SentryGlas®. Each material is suited for different applications.

Obscure glass is not completely transparent but has some level of distortion which can be created using texture, patterns, or decorative interlayers. Obscure glass is typically where privacy is needed, and some light is desired.

In the architectural and decorative glass industry, pattern glass has one side that features a design created by rolling the hot glass ribbon between two metal rollers. The type of design and its structure determine the level of translucence of the patterned glass. Depending on its use, it can be laminated, back painted and custom designed for a variety of uses.

Some patterned glass can also be tempered if the glass is thick enough for durability to ensure safety and security purposes.