Shot Bag Impact Testing for Interior Glass: Standards, Methods, and Performance Evaluation

Shot bag impact testing is the core dynamic safety evaluation for interior architectural glass, simulating the effect of a human body striking doors, partitions, railings, and shower enclosures. This article explains the test principle, sample requirements, classification criteria, and major international standards—including GB 15763, ANSI Z97.1, and EN 12600—used by accredited third-party laboratories to verify the impact safety of tempered and laminated safety glazing.

Technical Overview

Shot bag impact testing (also known as pendulum bag impact testing) is a dynamic mechanical test used to evaluate the impact resistance and post-breakage safety of flat safety glass installed in interior building applications. Because interior glass doors, sidelites, partitions, and balustrades are frequently subject to accidental human collision, safety glazing standards require proof that the glass either withstands a soft-body impact or breaks in a manner that does not cause serious cutting or piercing injuries.

The test principle simulates a soft human body impact. A bag made of leather or reinforced textile and filled with lead shot—with a total mass of approximately 45 kg (about 100 lb) in most standards—is suspended from steel cables to form a pendulum. The fully prepared glass specimen is clamped vertically in a rigid frame, and the shot bag is released from a specified drop height so that it strikes the center of the specimen. Depending on the drop height and the resulting breakage pattern, the glass is assigned a safety impact classification.

The principal reference standards include GB 15763.2 and GB 15763.3 (Chinese national standards for tempered and laminated safety glass), ANSI Z97.1 and 16 CFR 1201 (North American safety glazing specifications), and EN 12600 (European pendulum impact test method). All are widely recognized by accredited third-party laboratories and building authorities.

Testing Samples

Flat Tempered Glass

Tempered (fully toughened) glass is the most common sample type for interior safety glazing. Specimens are typically cut to 1930 mm × 864 mm, processed through the tempering furnace under normal production conditions, and submitted after the required cooling or aging period. The test verifies that, if breakage occurs, the glass disintegrates into small, relatively blunt particles rather than large sharp shards.

Laminated Safety Glass

Laminated glass specimens—consisting of two or more glass plies bonded by a polymeric interlayer such as PVB, EVA, or ionoplast—are tested to confirm that the interlayer retains fragments after breakage and resists penetration by the shot bag. Post-breakage integrity is especially critical for overhead glazing, railings, and barrier applications.

Insulating Glass Units and Composite Products

For insulating glass units and coated or decorated composites, the individual safety glass components are normally tested in accordance with the applicable safety standard. Where the finished product configuration materially affects impact behavior (e.g., filmed glass, printed patterns, or drilled and notched panels), testing is performed on the finished configuration rather than on plain stock.

Decorative and Post-Processed Interior Glass

Acid-etched, sandblasted, ceramic-frit printed, and safety-film applied glass used in doors, screens, and furniture may also be submitted. Surface treatments and edge work can influence impact performance, so specimens must represent the exact production process, including edge grinding and hardware cutouts.

Testing Items

Typical test and evaluation items for shot bag impact testing include:

• Impact resistance at specified drop heights (typically 300 mm to 1200 mm under GB standards; 457 mm and 1219 mm under ANSI Z97.1 and 16 CFR 1201)
• Safety impact classification of tempered glass (Class I, II, III by drop height under GB 15763.2; Class A and Class B under ANSI Z97.1)
• Breakage mode classification under EN 12600, distinguishing annealed-like, laminated-like, and toughened-like fracture behavior
• Verification that broken tempered glass fractures into small particles meeting particle-count and particle-size limits
• Penetration resistance of laminated glass—no pass-through of the shot bag and no opening permitting passage of a reference sphere
• Fragment retention and fallout limits after impact
• Specimen verification before testing: dimensions, thickness, edge quality, and visual defects

Testing Methods

Pendulum Shot Bag Method (GB 15763.2 / GB 15763.3)

Specimens of 1930 mm × 864 mm are conditioned to ambient laboratory temperature and rigidly clamped in a vertical test frame. A 45 kg leather shot bag filled with fine lead shot is suspended by wires from a fixed pivot and released from standardized drop heights of 300, 450, 600, 750, 900, or 1200 mm, striking the geometric center of the specimen. Tempered glass passes a given class if the specimens do not break, or if breakage produces particles that satisfy the fragmentation safety requirements of GB 15763.2. Laminated glass is evaluated under GB 15763.3 on the basis of whether the bag penetrates the specimen and whether glass fragments detach beyond permitted limits. Multiple specimens (typically four per condition) are tested to establish the classification.

North American Shot Bag Method (ANSI Z97.1 / 16 CFR 1201)

The North American method uses a shot bag of approximately 100 lb (45.4 kg) dropped from heights of 18 in (Class B) or 48 in (Class A). Specimens measuring 34 in × 76 in are mounted vertically and impacted at the center. The glass passes if it does not break, or if it breaks in a manner that does not create hazardous openings or dangerous fragment fallout—verified by criteria such as the inability of a reference sphere to pass through any resulting opening and limits on detached fragment size and mass.

European Twin-Tire Pendulum Method (EN 12600)

Although EN 12600 specifies a twin pneumatic-tire impactor of 50 kg rather than a shot bag, it serves the same purpose as the bag test and results are often compared for international projects. The impactor is dropped from 190 mm, 450 mm, or 1200 mm, producing classification codes such as 1B1, 2B2, or 3B3, in which the digit indicates the drop-height level and the letter indicates the mode of breakage. This classification system allows specifiers to select glass with an appropriate combination of impact energy absorption and safe fracture behavior.

General Test Conditions and Evaluation

In all methods, the specimen must be clamped without excessive prestress, the pendulum must strike perpendicular to the glass surface at the specified point, and the drop height must be controlled within tight tolerance. After impact, trained laboratory personnel examine the specimen for breakage, penetration, particle size, fragment retention, and the shape of any opening. The reported result includes the drop height, number of specimens, breakage description, and the resulting safety class, documented in a test report issued under the laboratory's accreditation scope.

Applications

Shot bag impact test reports are required or referenced across a wide range of interior glazing applications, including:

• Interior glass doors, frameless swing doors, and sliding doors in commercial and residential buildings
• Sidelites, transoms, and full-height glass partitions in offices, hotels, hospitals, schools, and airports
• Shower enclosures, bath screens, and bathroom glazing
• Glass balustrades, stair panels, and protective barriers where human body contact is foreseeable
• Display cases, showcases, and museum glazing
• Glass table tops, cabinet doors, and furniture components
• Interior glazing in kindergartens, sports halls, and other high-traffic public spaces
• Compliance verification for construction product certification, tender submissions, and regulatory acceptance of safety glazing materials

FAQ

What sample size and quantity are required for shot bag impact testing?

Under GB and ANSI methods, standard specimens measure 1930 mm × 864 mm. A minimum of four specimens per drop height is normally required so that both non-breakage and breakage behavior can be assessed statistically. Specimens must be representative of actual production, including the final edge finish and any holes or cutouts.

What does a "pass" result mean?

The criteria depend on the product type. Tempered glass passes if it either does not break at the specified drop height, or breaks into small blunt particles meeting the particle-count and fragment-size limits of the standard. Laminated glass passes if the shot bag does not penetrate the specimen, no unsafe opening is created, and fragment fallout and detachment remain within permitted limits.

How do GB, ANSI, and EN requirements differ?

GB 15763 uses a 45 kg shot bag with multiple drop heights (300–1200 mm) and classifies tempered glass into Classes I–III. ANSI Z97.1 and 16 CFR 1201 use a 100 lb bag dropped from 18 in or 48 in (Class B or Class A). EN 12600 uses a 50 kg twin-tire impactor dropped from 190, 450, or 1200 mm and classifies both impact energy and breakage mode. Accredited third-party laboratories can advise which regime applies to a given market and project specification.

Do temperature and conditioning affect the results?

Yes. Specimens are conditioned to a stable ambient temperature before testing, and testing is performed promptly after removal from conditioning. Extreme thermal gradients, poor edge quality, or damage during handling can significantly reduce impact performance and must be avoided during sampling and transport.

Can coated, filmed, or printed glass be tested?

Yes. Surface treatments, ceramic frit patterns, and applied safety films alter impact and fragmentation behavior, so such products should be tested in their finished configuration. The test report will state the exact product construction tested, allowing specifiers and regulators to confirm equivalence with the supplied product.