Document ID: chunk:federal_register_of_legislation:F2023C00228:front:0:p124
Version: federal_register_of_legislation:F2023C00228
Segment Type: other
Provision Reference: 
Character Range: 334164–336951

the measurement described in paragraph 2.2.3.1. below have been carried out, the outer face of the said three samples shall be treated as described in paragraph 2.2.2.2. with the mixture defined in paragraph 2.2.2.1. below.

       2.2.2.1. Test mixture

       The test mixture shall be composed of 61.5% n-heptane, 12.5% toluene, 7.5% ethyl tetrachloride, 12.5% trichloroethylene and 6% xylene (volume %).

       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 an effort of 100 N applied on a test surface of 14 x 14 mm.

       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. (Resistance to detergents) 23 degrees C +/- 5 degrees C.

       Afterwards the samples shall be carefully rinsed with distilled water containing not more than 0.2% impurities at 23 degrees C +/- 5 degrees 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

       measured on the three samples according to the procedure described in appendix 2 to this annex shall not exceed 0.020 (delta 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

       measured on the three samples according to the procedure described in appendix 2 to this annex shall not exceed 0.020 (delta dm < 0.020).

       2.3. Resistance to detergents and hydrocarbons

       2.3.1. Resistance t detergents

       The outer face of three samples (lenses or samples of material) shall be heated to 50 degrees C +/- 5 degrees C and then immersed for five minutes in a mixture maintained at 23 degrees C +/- 5 degrees C and composed of 99 parts distilled water containing not more than 0.02% impurities and one part alkylaryl sulphonate.

       At the end of the test, the samples shall be dried at 50 degrees C +/- 5 degrees 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 then be lightly rubbed for one minute with