Sheet material containing thermoplastic fibres which has been provided with a pattern formation by a mechanical process (see Group XVI) may be subsequently treated with hydrochloric or sulphuric acid. In one example a heat-set nylon fabric, after calendering, is shrunk with 10 per cent hydrochloric acid at 65 DEG C. for 30 seconds without tension and then washed and dried. In another example a nylon percale, after calendering, is subjected to a delustering treatment with 28.5 DEG B<\>e sulphuric acid at 10 DEG C. for 7 seconds, and then washed and dried. In a similar example a nylon toile is delustered by treatment in a 29 B<\>e sulphuric acid solution at 15 DEG C. for 7 seconds.ALSO:In a process involving mechanical treatment in apparatus having a heated forming member for the production of mechanical pattern formations on sheet materials which contain thermoplastic materials, such as knitted goods and woven or unwoven fabrics, resists are applied to the sheet material in pattern form which govern the heat transferred from the heated forming member to the sheet material during the mechanical treatment. In one example a heat-set nylon fabric is printed with a heatinsulating resist of gum Arabic solution, water and turpentine. The fabric is then calendered to a high glaze at 150 DEG C., shrunk by treatment with 10 per cent hydrochloric acid solution and then washed and dried. In another example a nylon percale is printed with a resist of hexamethylene tetramine, water, gum Arabic, starch and tragacanth. It is then calendered at 135 DEG C. and the resist is washed out. The cloth is then subjected to a delustering treatment with 28.5 DEG Be. sulphuric acid solution at 10 DEG C. In a further example a nylon toile delustered with 29 DEG Be. sulphuric acid at 15 DEG C. is printed with a paste of dextrin, powdered nylon substance and water. Cotton flock is then blown on and retained by the paste. The cloth is then cold calendered and then hot calendered at 140 DEG C. The resist is then washed out and the cloth is dried.ALSO:In a process involving mechanical treatment in apparatus having a heated forming member for the production of mechanical pattern formations on sheet materials, which contain thermoplastic materials, such as fabrics, knitted goods, films, plastic material, unwoven fabrics and laminated goods, heat-insulating resists are applied to the sheet material in pattern form which govern the heat transferred from the heated forming member to the sheet material during the mechanical treatment. The resist covered areas, which are shielded from the heating effects of the forming member are either unaffected by the mechanical treatment or affected to a lesser extent than the areas not covered by resist. The resists are composed mainly of a substance which has a coefficient of heat conductivity of 0.05 or less at a temperature of 30 DEG C when applied to the sheet material. The amount of heat transferred through the resist may be further reduced by using substances which first begin to melt or soften in the deforming operation and which therefore absorb latent heat for fusion. The resist may be adapted to adhere only temporarily to the sheet material so as to be easily removable or it may become permanently fixed to the sheet material. Examples of self adhering resists agents are gum arabic, British gum, tragacanth gum, starch, gelatine, albuminous substances and casein substances; solutions of cellulose derivatives and varnishes, and other self-adhesive resists and their products of de-composition. Examples of resist agents which will not adhere by themselves are talcum powder, sawdust, bonemeal, cellulose, kieselguhr, cork, cotton fibres, wool fibres, artificial silk fibres, asbestos fibres or the fibre flock thereof. These agents are applied with fixing agents effecting at least a temporary adhesion. The resist agent may be applied by printing in a conventional textile printing machine having rollers formed with patterns, stencils of all kinds or stamps. Alternatively an adhesive may be applied as p above and the resist agent applied to the adhesive, e.g. by spraying in the form of flock, or powder. In another method a film or sheet of the resist material is bonded to the sheet to be treated and dissolved or chemically removed in parts to leave the desired pattern. Alternatively the sheet may be printed with a printing paste adapted locally to prevent the bonding action between the resist film, which is subsequently applied, and the sheet. Parts of the resist film may then easily be removed, e.g. by washing and by use of solvents if necessary. The resists may be applied in the form of a solution, a colloid, a dispersion or an emulsion. The resist may also contain substances with better conducting properties, e.g. dye stuffs, pigments, metal powders which are permanently fixed on the thermoplastic material. The mechanical treatment to produce the effects required may consist in rolling between smooth calender rollers with or without friction, or rollers engraved with patterns or having hatchings or raised relief-like embossed designs. The treatment is carried at a temperature at which the thermoplastic in the sheet material is capable of being deformed. Alternatively the mechanical treatment may comprise pressing or stamping to produce a glaze or lustre finish. Two or more different mechanical treatments may be used in succession on the same sheet material. The resist may be adapted to prevent thermoplastic deformation or merely to reduce the deforming effects of the mechanical treatment when modified as described above. Two or more different resists may be applied to the sheet material to produce patterns having different degrees of deformation. After treatment according to this invention, the material may be subjected to further treatment, e.g. it may be bleached, dyed, printed, matted finished, cold-calendered or shrunk. The last mentioned treatment causes a creping of selected parts, e.g. the parts covered by the resist.