Scope:

The standard method ASTM C1651 helps determine the peak-to-valley depth and the wavelength of a roll wave in flat glass and then selecting the optical distortion resulting from that rolling wave. Peak-to-valley measurements provide a way of monitoring the roll wave distortion which occurs in flat, heat-treated architectural glass substrates processed in a heat processing continuous or heat-treated furnace in which rollers are used to convey the glass. Calculated peak-to-valley depth gives the information required by some specifiers of heat-treated flat glass products.

Test Procedure:

The test method ASTM C1651 comprises relocating an instrument across the glass surface parallel to the direction that the glass substrate traveled during heat processing. The device will predominantly measure the glass surface’s out-of-plane deformation, which is characteristic of the glass and known as “roll wave.” The peak-to-valley depths of the roll waves, W, and the peak-to-peak distances, L, are measured.

The instruments are used in two methods named as:

Specimen Size

Flat bottom plate Length ≥ 12 inches (305 mm).

Flat bottom plate width  ≥ 2 inches (50.8 mm).

Data:

Distance of peaks = P₁,P₂,….P_n

Distance to valley = V₁, V₂,….V_m