or more components in successive measurements within the garment produces the bar code and comparison with the known and genuine data for an authentic garment provides the means of authentication it should be appreciated that the bar code incorporated in the garment may indicate various types of information including for instance the date and time of manufacture of the fabric the product owner and the manufacturer any garment can be readily checked to see if it carries the information which is appropriate for the genuine articles the codes may be changed frequently and as a result it is impossible for a would be copier to know which bar codes to apply to a batch of garments even if he were able to incorporate appropriate components into the yarns which he uses in another embodiment of the present invention textile material for instance woven or knitted fabric is treated in bulk after the formation of the textile or as part of secondary or subsequent treatment of the fabric known as u201c finishing u201d in such post formation treatments the textile has applied to it sufficient of one or more components so as to cause the alteration of the response of the textile to incident electromagnetic radiation the or each component may be applied in such a way as to result in the inclusion of the component in the textile so as to give a response to incident electromagnetic radiation which is characteristic of the presence of the component at specific points within the textile accordingly the presence of the component in the appropriate sequence is the indicator of the authenticity of the.