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BNP Media is a Registered

Provider with The American

Institute of Architects

Continuing Education Systems.

Credit(s) earned on

completion of this course will

be reported to AIA CES for AIA

members. Certificates of

Completion for both AIA

members and non-AIA

members are available upon

request.

This course is registered with

AIA CES for continuing

professional education. As

such, it does not include

content that may be deemed

or construed to be an approval

or endorsement by the AIA of

any material of construction or

any method or manner of

handling, using, distributing, or

dealing in any material or

product.

_____________________________________

Questions related to specific materials,

methods, and services will be addressed at

the conclusion of this presentation.

Learning Objectives• State the two main reasons for heat-

treating glass

• Describe the differences in characteristics

between fully tempered glass and heat-

strengthened glass

• List two typical applications for fully

tempered glass

• Explain the three phases of heat-treating

glass

Why Flat Glass is Heat-Treated

• To make the glass stronger to increase

resistance to mechanical and thermal

stresses

• To achieve desired break patterns for a

safety glazing product

Types of Heat-Treated Glass• Fully Tempered Glass: flat or bent glass

that has been heat-treated to have either a minimum surface compression of 10,000 psi (69 MPa) or an edge compression not less than 9,700 psi (67 MPa) or meet ANSI Z97.1

• Heat-Strengthened Glass: flat or bent glass that has been heat-treated to have a surface compression between 3,500 psi (24 MPa) and 7,500 psi (52 MPa)

Characteristics of Heat-Treated Glass

• Fully Tempered Glass

• Under uniform loading – approximately four

times as strong as a lite of annealed glass (of

same size and thickness)

• Improved resistance to thermal stress, thermal

shock and impact

• Breakage pattern – fractures into relatively small

pieces – reducing the likelihood of serious cutting

or injuries

• Meets safety glazing requirements when

produced to meet the requirements of CPSC 16

CFR 1201 and ANSI Z97.1

• Heat-Strengthened Glass

• Under uniform loading – approximately twice as

strong as a lite of annealed glass (of same size

and thickness)

• Improved resistance to thermal stress, thermal

shock and impact as compared to annealed glass

• Break pattern similar to annealed glass and

therefore more likely to remain in opening than

tempered glass

• Not a safety glazing material

• Less likely to have spontaneous breakage from

inclusions than tempered glass


Photos courtesy of SW Joehlin and Universal Windows


• Glass Properties

• Glass Fabrication

• Optical Properties

• Glass Surface


• Glass Properties Unchanged By Heat-Treating

o Color

o Clarity

o Chemical composition

o Deflection

o Modulus of elasticity

o Density

o Specific heat capacity

o Thermal conductivity

o Emissivity

o Light transmittance

o Reflectance


• Glass Fabrication

• Heat-strengthened and fully tempered glass

CANNOT be cut or drilled after heat-treating

• Edge shaping, sandblasting, etching and v-

grooving should not be done after heat-treating

because it decreases the strength of the glass


• Optical Properties

• Bow, roll wave and strain

pattern are inherent

characteristics

• Insulating glass units

containing high performance

coatings and/or multiple

layers of heat-treated glass

will magnify these

characteristics

• Aesthetic issues do not affect

the physical performance of

the product


• Glass Surface

• Microscopic surface particles, roll marking or

dimpling can occur

• Typically not visible to the human eye under normal

viewing conditions

• Does not affect the physical performance of the glass

• Microscopic surface particles, roll marking or dimpling

can occur

NOTE:

• Allowable under ASTM C1036 & ASTM C1048


• Breakage

• Occurs when surface compression layer is compromised

• Spontaneous breakage of tempered glass may occur days or

even months after the initial damage, therefore the cause is

not readily apparent

• Common Causes of Breakage

• Surface or edge damage

• Deep scratches or gouges

• Severe weld splatter

• Missile / windborne debris impact

• Glass to metal contact

• Wind/thermal loading

• Inclusions


• Inclusions

• Includes stones, seeds and bubbles

• Size and frequency is addressed in ASTM C1036

Standard Specification for Flat Glass• Most inclusions do not affect glass performance

or cause glass breakage


• Nickel Sulfide Inclusions

• Nickel sulfide is an undesirable organic compound

that can be present in float glass

• Certain nickel sulfide inclusions can expand with

time/temperature and may cause breakage

• Heat soaking techniques have been used to

reduce spontaneous breakage in the field from

nickel sulfide inclusions

• Due to the lower stress levels of heat-

strengthened glass spontaneous breakage from

nickel sulfide is extremely rare


• Safety Glazing Applications Defined By

Building Codes

• Tub and shower enclosures

• Patio doors and entry systems

• Glass baluster

• Restrictions as defined by local codes

• Other Architectural Applications

• High wind load conditions

• High impact resistance conditions

• Fire break-out lites

• Emergency entrance/exit

Architectural Applications of Fully Tempered Glass

Other Typical Applications for Fully Tempered Glass

• Microwave, oven & toaster doors

• Light fixtures

• Refrigerator shelves and doors

• Furniture

• Shelving and table tops

• Solar glass

• Transportation

• Automobile & bus (side lites, back lites and

sunroofs)

• Heavy equipment cab glazing

• Marine vessel glazing

• Sports Facilities

• Basketball backboards

• Hand and racquet ball courts

• Hockey rink side boards

Other Typical Applications for Fully Tempered Glass

Architectural Applications of Heat-Strengthened Glass

• Where additional strength is desired,

but not requiring the strength of fully

tempered glass

• Applications where glass fall-out

resistance is desired (stay in frame)

Architectural Applications ofHeat-Strengthened Glass

• Recommended for high solar

absorption and thermal stress

conditions

• Tinted glass substrates with coatings

• Applications where partial shading is a concern

(temperature difference)

• Poorly ventilated interior conditions

• Spandrel glazing applications

• Glass with decorative opaque or silk screened patterns

• Does not meet safety glazing

requirements (ANSI Z97.1 and CPSC 16

CFR 1201 )

How Flat Glass is Heat-Treated• The processing of heat-treating

includes three phases:

• Pre-Processing

• Heat-Treating

• Testing and Inspection

• Typical Pre-Processing Steps

• Annealed float glass cut-to-size

Photos by Viracon

How Flat Glass is Heat-Treated


• Holes

• Notches

• V-grooving fabrication

Photos by Edgeworks



• Edging

Definitions of the surfaces for edge finishes used above are as follows:1. “GROUND” Surface exhibits fine linear and random abrasion marks, rough in appearance.2. “SMOOTHED” Surface with a frosted appearance which diffuses any reflected light.3. “POLISHED” Surface is reflective in appearance similar to the major surface of glass.

Arrissed Edge

Bevel

Feathered Edge

Flat Edge

Mitre Bevel

Round Edge

Seamed Edge

Swiped Edge



• Sandblasting

• Etching

Etched Sandblasted

Photo by Viracon



• Product/identification marking

• Etched

• Laser

• Sandblasted

• Silk-screened (ceramic frit)

Photo by Viracon



• Glass completely washed and dried

Photos by Oldcastle BuildingEnvelope®


• Heat Treating Process

• Glass transported and loaded onto the furnace

heating section and evenly heated to

approximately 1150°F (621°C) using radiation,

convection and/or conduction

Video by Glaston


• Heat Treating Process

• Glass transported from furnace heating section

through the quench section using concentrated

air to establish surface and edge compression

Graphic by Viracon



• Fabricators inspect finished product for optical quality

Photos from Strainoptics, LiteSentry, R&D Reflections

Flat Bottom Roll Wave Gauge

3-point Bottom Roll Wave Gauge

Zebra Board Inspector G

Osprey® 5



• Center punch fragmentation quality assurance

testing (destructive)

Photos by Viracon/Video by Intertek



• Impact test (destructive)

• Required by CPSC 16 CFR 1201 and ANSI Z 97.1

Graphic from Engineering Standards Manual/ Video from Intertek



• Surface and edge stress measurement (non-destructive)

Photos by Strainoptics

Surface Stress Measurement DevicesEdge Stress Measurement Devices


Learning Objectives• State the two main reasons for heat-

treating glass

• Describe the differences in characteristics

between fully tempered glass and heat-

strengthened glass

• List two typical applications for fully

tempered glass

• Explain the three phases of heat-treating

glass

Industry ResourcesNational Glass Association glass.org

► Glass Informational Bulletins► Glazing Manual► Engineering Standards Manual► Guide to Architectural Glass

ASTM International www.astm.org► ASTM C1036 Standard Specification for Flat Glass ► ASTM C1048 Standard Specification for Heat-Strengthened

and Fully Tempered Flat Glass► ASTM C1279 Standard Test Method for Non-Destructive

Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully Tempered Flat Glass

► ASTM C1651 Standard Test Method for Measurement of Roll Wave Optical Distortion in Heat-Treated Flat Glass

► ASTM C1652 Standard Test Method for Measuring Optical Distortion in Flat Glass Products Using Digital Photography of Grids

► ASTM E1300 Standard Practice for Determining Load Resistance of Glass in Buildings

Industry Resources

American Architectural Manufacturers Associationwww.aamanet.org

ASTM Internationalwww.astm.com

Insulating Glass Manufacturers Alliancewww.igmaonline.org

Glass Magazinewww.glass.org

Safety Glazing Certification Councilwww.sgcc.org

USGlass Magazinewww.usglassmag.com

Industry Resources

http://www.astm.com/

http://www.astm.com/

http://www.igmaonline.org/

http://www.glass.org/

http://www.sgcc.org/

http://www.usglassmag.com/

ConclusionThis concludes The American Institute of Architects

Continuing Education Systems Course

Understanding Applications for Heat-Treated Glass

1945 Old Gallows Rd Ste 750Vienna, VA 22182

703.442.4890

www.glass.org

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