The purpose of this document is to provide information about a procedure based on the determination of a visual index correlated with the content of textile fibres, which are free and bounded to the rubber, of granulates. This approach is currently used by Spanish grinders in order to control the efficiency of their processes and is effective for granulates with particle sizes the bottom limit of which is more than 0,5 mm, and upper limit less than 10 mm. NOTE Part of this document is also the presentation of a study carried by Valoriza Servicios Medioambientales and Geneus Canarias S.L. A test procedure for the determination of a visual index of the content of the textile fibre of a granulate sample, which is free and bounded to the rubber, from the ELT’s processing is described in UNE 53936:2015 EX: Materials produced from end of life tyres. Rubber granulates.