Curved Glass

Curved Toughened / Heat Strengthened - Critemp®

Tróia Design Hotel

Bombay Sapphire Distillery

Puente Champalimaud

Centro Cultural Óscar Niemeyer

Edificio Zurich

Rolex Learning Centre


Curved toughening and heat strengthening are fast bending processes that help hardening the glass and speeding up production.

Having all the edgework done before hand (edge polishing, holes, notches, etc.), the flat glass ply gets into the oven to be heated up to about 600ºC, temperature at which the oven rollers bend up curving the glass in one single radius and with no need for a steel mould. Immediately afterwards, the already curved geometry is quenched (fast cooling).
As a result, the molecular structure of the material is altered and high compressive stresses appear on the glass surfaces, improving its resistance to mechanical, compressive and impact stresses.

Curved toughening and heat strengthening open the door to the use of the most powerful low-E and high selectivity coatings, normally very transparent with good G-Value and U-Value (1.0 W/m2-K in IGU; 0.6 W/m2-K in triple glazing). It is mandatory for coatings to be on the concave surface of the bend glass, unless we are working with hard ones. This technology is commonly used in large projects where glass is cylindrical, when there is a lot of repetition. Regretfully, current tempering ovens in architecture can just make single radius. Hence, no J-shapes, U-shapes, double curvature, …are available.


General Details

• Fast bending process (approx. 15min). Speed depends on thickness.

• Heat strengthened panel is produced in the same oven as toughened ones. The only difference is the slower quenching.

• All the coatings that can be toughened flat, can be specified. Final feasibility depends on radius, thickness and even aspect ratio. Coatings always on concave surface, unless hard coatings are being used. For further information in this regard, please contact us.

• When there is lamination, thicknesses rather be the same (6+6mm, 8+8mm, …). 

• Coloured interlayers are not advisable as a mottled effect can show up. 

• High security interlayers can be used.

• Anisotropy and roller wave distortions have to be taken into account as are inherent to the process.

• Curvature tolerance is control with a pass/no-pass gauge which is bigger in half the thickness of the thickest glass ply in the composition.

• High post-bending stresses (Toughened >90MPa;  Heat Strengthened 40-60MPa).

• Breakage occurs in small parts called dice with non-cutting edges.

• PVB and SentryGlas can be used, normally 1.52mm or thicker.


DIMENSION OVEN 1:  2440 X 4500 mm   /    96” X 177”
DIMENSION OVEN 2:  4200 X 3200 mm   /  165” X 126”
DIMENSION OVEN 3:  1500 X 3200 mm   /    59” X 126”

(For larger dimensions, please contact us )