Specifies a method for operating laboratory equment. It does not attempt to define either the minimum accetable standard or the precise techniques to be adopted for the test; these are to be the subject of agreement between the interested parties. The posible forms which the test requirement may take are the following: The test material shall be at least as ligthfast as a specified wool scale pattern exposed simultaneously or an agreed paint sample exposed simultaneously. It should show no greater change within a specified period than a previously exposed reference sample. Exposure to light from artificial sources under prescribed conditions.