Document ID: chunk:federal_register_of_legislation:F2023C00228:reg:7:p10
Version: federal_register_of_legislation:F2023C00228
Segment Type: reg
Provision Reference: reg 7 (pt 10/12)
Character Range: 618252–621001

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  Δ 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 , 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 then be lightly rubbed for one minute with a cotton cloth soaked in a mixture composed of 70 per cent n-heptane and 30 per cent toluene (volume per cent), and shall then be dried in the open air.

       2.3.3. Results

       After the above two tests have been performed successively, the mean value of the Δvariation in transmission , measured on the three samples according to the procedure described in Appendix 2 to this annex shall not exceed 0.010 (tm  0.010).

       2.4. Resistance to mechanical deterioration

       2.4.1. Mechanical deterioration method

       The outer face of the three new samples (lenses) shall be subjected to the uniform mechanical deterioration test by the method described in Appendix 3 to this annex.

       2.4.2. Results

       After this test, the variations:

       in transmission: ,

       and in diffusion: ,

       shall be measured according to the procedure described in Appendix 2 in the area specified in paragraph 2.2.4.1.1. of this Regulation.  The mean value of the three samples shall be such that:

       tm  0.100;

       tm  0.050

       2.5. Test of adherence of coatings, if any

       2.5.1. Preparation of the sample

       A surface of 20 mm x 20 mm in area of the coating of a lens shall be cut with a razor blade or a needle into a grid of squares approximately 2 mm x 2 mm.  The pressure on the blade or needle shall be sufficient to cut at least the coating.

       2.5.2. Description of