Document ID: chunk:federal_register_of_legislation:F2023C00154:front:0:p35
Version: federal_register_of_legislation:F2023C00154
Segment Type: other
Provision Reference: 
Character Range: 90372–92886

cent n-heptane, 12.5 per cent toluene, 7.5 per cent ethyl tetrachloride, 12.5 per cent trichlorethylene and 6 per cent xylene (volume per cent).
2.2.2.2. Application of the test mixture
Soak a piece of cotton cloth (as per ISO 105) until saturation with the mixture defined in paragraph 2.2.2.1. above and, within 10 seconds, apply it for 10 minutes to the outer face of the sample at a pressure of 50 N/cm2, corresponding to a force of 100 N applied on a test surface of 14 x 14 mm.
During this 10-minute period, the cloth pad shall be soaked again with the mixture so that the composition of the liquid applied is continuously identical with that of the test mixture prescribed.
During the period of application, it is permissible to compensate the pressure applied to the sample in order to prevent it from causing cracks.
2.2.2.3. Cleaning
At the end of the application of the test mixture, the samples shall be dried in the open air and then washed with the solution described in paragraph 2.3. below (resistance to detergents) at 23 °C ± 5 °C.
Afterwards the samples shall be carefully rinsed with distilled water containing not more than 0.2 per cent impurities at 23 °C ± 5 °C and then wiped off with a soft cloth.
2.2.3. Results
2.2.3.1. After the test of resistance to atmospheric agents, the outer face of the samples shall be free from cracks, scratches, chipping and deformation, and the mean variation in transmission
∆ t = (T2 - T3) / T2,
measured on the three samples according to the procedure described in Appendix 2 to this annex shall not exceed 0.020 (∆ tm ≤ 0.020).
2.2.3.2. After the test of resistance to chemical agents, the samples shall not bear any traces of chemical staining likely to cause a variation of flux diffusion, whose mean variation
∆ d = (T5 - T4) / T2,
measured on the three samples according to the procedure described in Appendix 2 to this annex shall not exceed 0.020 (∆ dm ≤ 0.020).
2.3. Resistance to detergents and hydrocarbons
2.3.1. Resistance to detergents
The outer face of three samples (lenses or samples of material) shall be heated to 50 °C ± 5 °C and then immersed for five minutes in a mixture maintained at 23 °C ± 5 °C and composed of 99 parts distilled water containing not more than 0.02 per cent impurities and one part alkylaryl sulphonate.
At the end of the test, the samples shall be dried at 50 °C ± 5 °C. The surface of the samples shall be cleaned with a moist cloth.
2.3.2. Resistance to hydrocarbons
The outer face of these three samples shall