Transparency and Reflection

• To The transparency of a curved glass should not be impaired considerably. However, so-called burn marks can appear depending on glass thickness and geometry.
• Due to optical laws the reflection of curved glass is always different from the reflection of planar glass.
• The reflection behavior is impaired by the following criteria:
• Strong self reflection of the basic glass (e.g. sun protection glass or other coatings).
• Close bending radii
• Large bending angles (e.g. more than 90°)
• Tangential extensions
• Glass thickness > 8 mm


• The acceptance of surface damages is subject to the fact whether they are still visible from a distance of 3 m, daylight and perspective.
• The same shall apply to damages with regard to colour, reflection and light transmission.
• Inspection of glass always in daylight from inside (concave side) to outside (convex side).
• Coating defects must not be visible from more than 3 m distance.
• For glass defects, see directive BV Fachglas e.V.
• Roundness parameters

The (inner) radius of curved glass must be between two concentric circles which are on the same level.

Döring Glas is an certified company according to
DIN EN ISO 9001 Quality
Management System.

We produce CE certified curved insulating glass
products according to European
Standard EN 1279.

The German Institute for Construction Technology, Berlin (DIBt) garanted general planning approval for curved glazing with the best, than ever certified values in Germany.

A Compliance Certificate for AbZ (General Construction Approval) is available upon request in form of order-related factory certificate according to EN 10204. Labelling of glass is done by silk-print or sandblasting stamp only upon on customer request.

Example Factory Certificate
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Tolerances and Visual Assessment:

For all curved glass products, manufactured in our company,†the general tolerance and conditions in accordance to "Guideline for thermal bend architectural glass products ", BF-datasheet 009/2011 from Bundesverband Flachglas e.V. and the "Guideline to Assess the Visible Quality of Glass in Buildings." are valid (unless otherwise agreed in writing).

Guidelines for thermally-curved glass in the building industry by Bundesverband Flachglas
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Examination results acc. EN 10204
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