two panels one of which is opaque and the other of which is clear the opaque panel being of a foam material and or having a surface which would comprise an inner surface of an envelope with heat reflective characteristics with such an envelope heat dissipated from a head of hair being treated will pass inwardly through the material of the envelope but not outwardly from the envelope and will thus assist in the process of treatment of selected strands of the hair contained within the envelope which process is enhanced by the presence of an environment at elevated temperature the folds 29 30 and 34 of the sheets 25 31 and 37 may be formed by means of a fold line provided by perforating or creasing the material of the sheets referring now to fig1 there is shown at a a sheet 1 21 25 31 or 37 when used in a process of coloring selected strands of hair the sheet has been located under selected strands of hair a leading edge of the sheet having been located adjacent the scalp and has then been folded transversely to form an envelope containing the selected strands of hair the whole of the strands is contained within the envelope in consequence the whole of the strands is subjected to the effects of the coloring substance with which the strands have been coated including the portions of the adhesive in contact with the strands since the adhesive is removed from contact with the strands in the presence of the coloring substance an alternative method of application is shown at b in fig1 which is achieved with either of sheets 1 or 21 by rolling the sheet after attachment to selected.