Architectural glass is manufactured within defined tolerances. Problems arise when drawings, standards and visual expectations use different assumptions. Agreeing measurable acceptance criteria before production is more effective than trying to resolve subjective expectations after delivery.
Start with the governing product standard
The base standard depends on whether the product is flat, tempered, laminated, insulating, coated, printed or curved. A multi-process unit can be affected by several standards, while the contract or project specification may include tighter requirements.
For flat glass produced to Chinese standards, GB 11614-2022 is a common starting reference. Export projects should use the destination code and agreed product standards.
Dimensional and fabrication tolerances
Confirm the tolerance for overall width and height, squareness, thickness, edge finish, corner treatment, hole diameter and position, notches and cut-outs. Larger panels, thick laminated make-ups and curved glass can require different practical limits.
- Dimension every feature from a stable datum.
- Avoid conflicting dimensions on revisions.
- Identify critical hardware interfaces.
- State whether dimensions refer to glass or opening size.
- Allow practical clearances for installation.
Flatness, bow and roller wave
Heat treatment can introduce overall bow, local bow and roller wave. These effects influence reflected images, edge alignment and façade appearance. The measurement method, orientation and acceptance limit should be agreed using the applicable standard.
Large reflective façade panels can make small variations more visible. A full-size visual mock-up is useful when reflection quality is a primary design requirement.
Optical appearance and anisotropy
Tempered glass can show optical distortion and anisotropy under polarized light. Coated and insulating units can also display colour shifts, interference effects or reflection differences due to angle, sky conditions and interior background.
These phenomena should be discussed separately from surface defects. Define the viewing direction, distance, daylight conditions and whether the glass is viewed in transmission or reflection.
Colour, coating and ceramic frit
For ceramic frit glass, agree colour reference, coverage, pattern, print orientation and viewing side. For coated products, identify manufacturer and coating code, surface position and allowed batch variation. Samples should be labelled, signed and retained when colour matching is critical.
Visual quality inspection
Specifications should state how scratches, bubbles, inclusions, edge chips, coating marks, sealant appearance and other features are evaluated. Inspection distance, lighting, background and observation time can change the result. Avoid undefined language such as ‘no defects’ unless a measurable project protocol accompanies it.
Record the agreement
Use approved drawings, sample records, inspection criteria, revision control and packing identification. If third-party inspection, witness points or project-specific reports are needed, include them before order confirmation.
Review our technical quality guidance and send your acceptance criteria for review.