ASTM C1048 Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass

Get Certified ASTM C1048 Testing for Heat-Strengthened and Fully Tempered Flat Glass

Manufacturers, fabricators, architects, glazing contractors, and quality-control professionals can use the ASTM C1048 testing method to ensure that heat-strengthened and fully tempered flat glass is able to meet specified requirements. The dimensional conformity, flatness, compression of the surface and edges (where applicable), glass quality, and coating performance may be tested and inspected. These assessments will yield documented information for production control, product qualification, purchasing specifications and project quality assurance. A competent testing specialist can also assist in deciding which requirements are applicable for the glass condition, the coating, the thickness, the configuration of the fabrication, and the intended use.

• Glass type: Heat-strengthened Kind HS and fully tempered Kind FT flat glass.
• Surface condition: Uncoated surfaces, ceramic-coated spandrel glass, and other coated glass.
• Glass form: Transparent or patterned flat glass meeting the applicable requirements.
• Manufacturing process: Heat treatment using a horizontal heat-treating system.
• Fabrication: Cutting, edgework, holes, notches, cutouts, grinding, sandblasting, etching, and related fabrication performed before heat treatment as specified.
• Dimensional requirements: Thickness, length, width, tolerances, and flatness requirements.
• Heat-treatment characteristics: Applicable surface or edge compression and break-pattern requirements.
• Coated glass: Requirements related to ceramic coating expansion fit, porosity, and durability where applicable.
• Limitations: Bent glass and glass manufactured using a vertical heat-treating system are outside the scope.

What are the uses of ASTM C1048 Testing?

ASTM C1048 testing is used to ensure the quality and specified characteristics of heat-strengthened and fully tempered flat glass. It is used to provide a common basis for assessing glass delivered for building and other uses. Testing can be part of manufacturing quality-control programs, supplier qualification, incoming inspection, and project-specific verification. The requirements may also be used for the specification of heat-treated glass in architectural glazing systems. Common uses include:

• Building glazing: Verification of heat-treated glass used in windows, doors, façades, partitions, and other architectural systems.
• Quality control: Monitoring dimensional, flatness, heat-treatment, and visual characteristics.
• Product qualification: Evaluating glass before acceptance for a specified application.
• Coated spandrel glass: Assessment of ceramic-coated glass where applicable.
• Fabrication verification: Checking glass after required pre-tempering fabrication and heat treatment.
• Purchasing and acceptance: Providing standardized requirements for manufacturers, fabricators, and purchasers.
• Project quality assurance: Supporting documentation that supplied glass conforms to specified ASTM requirements.

Which Materials Can Be Tested According to ASTM C1048?

ASTM C1048 applies primarily to monolithic flat glass products that undergo heat strengthening or full tempering. The glass may be transparent or patterned and may be supplied with or without coatings, provided the product falls within the scope of the specification. Applicable material categories include:

• Heat-strengthened flat glass (Kind HS): Flat glass processed to develop the specified heat-strengthened stress condition.
• Fully tempered flat glass (Kind FT): Flat glass processed to develop the specified fully tempered condition.
• Uncoated glass (Condition A): Glass supplied without a coating.
• Ceramic-coated spandrel glass (Condition B): Glass with a ceramic coating used for spandrel applications.
• Other coated glass (Condition C): Flat glass incorporating other specified coatings.
• Transparent or patterned glass: Glass products meeting the applicable quality and dimensional requirements.

Why is ASTM C1048 Testing Important?

The stress levels and fracture behavior of flat glass are affected by heat treatment, and it is crucial for construction applications to achieve consistency in processing and verification. ASTM C1048 gives a common specification for testing the properties of heat-strengthened and fully tempered glass. The specification also notes that a pattern of strains may be caused in heat-treated glass, which may be discernible under certain lighting conditions.  Flatness and deflection behavior can also affect the design and appearance of glazing systems, so the glass characteristics need to be considered together with the support system and expected loading. ASTM C1048 testing therefore helps identify dimensional, flatness, stress-condition, break-pattern, coating, and workmanship characteristics that may affect the suitability of the supplied glass.

ASTM C1048 Testing Process and Data Collection

Technicians identify the glass product, its thickness, kind, coating condition, finished dimensions, and fabrication configuration. The specimen or production panel is then examined using the applicable dimensional, flatness, visual, stress, break-pattern, or coating evaluation required by the specification. Fabrication features such as holes, notches, cutouts, bevels, and edgework are documented because these features are intended to be completed before heat treatment. The analyst or technician compares measured characteristics with the applicable ASTM C1048 requirements and any additional purchaser or project requirements. The final report should identify the glass, thickness, kind, condition, dimensions, coating where applicable, test or inspection performed, measured values, applicable acceptance requirements, and observed results.

Common Challenges and Troubleshooting

One common challenge is distinguishing dimensional or flatness variation caused by the heat-treatment process from defects in the original glass. Heat-treated glass is not necessarily as flat as annealed glass, and the degree of deviation can depend on thickness, size, and processing conditions. Careful setup of the instrument and positioning of the specimen is also an important factor in stress measurement. Technicians should apply the proper calibration and measurement techniques and make sure the technique to be used is appropriate for the glass condition. In evaluating the expansion fit and durability of coated glass, representative coating thickness and curing and production conditions are important.

• Technicians enter the specimen or production-glass identification, type of glass, condition, thickness, coating data, test conditions, and measured data. Dimensional measurement results are typically presented in mm, stress in MP, and coating or fracture results per the applicable referenced test method. ASTM C1048 requires that dimensional basis be in SI units.
• By measuring stress characteristics, dimensional conformity, flatness, and applicable break behavior of heat-treated glass, the analyst interprets the results against the product’s specified requirements. In cases of ceramic-coated glass, the measurements for the coating are compared to the expansion-fit, the porosity, and the durability requirements.
• The final report shall specify the type of material and product, type of glass, condition of glass, dimensions of specimens, type of tests conducted, results of tests, environmental conditions or test conditions, and conformance to the requirements. Reproducible and comparable quality control results are achieved with consistent specimen selection, calibrated measurement equipment, controlled testing, and accurate documentation.

Link to ASTM C1048