The invention describes a machine (10) for the in-line transformation of single-use products, comprising at least one unwinding group (12) for one or more reels (14) of web-shaped material (100), which constitutes the base support for said product, at least one printing group (18), arranged downstream of said unwinding group (12), capable of heat-printing decorative patterns, trademarks and/or inscriptions with a paraffin or natural wax-based ink (W) and/or mixtures thereof on the web-shaped material (100), and at least one folding and cutting group (20), arranged downstream of the printing group (18), wherein the printed web-shaped material (100) is folded and cut to form said products. The printing group (18) is provided with at least one melting or fluidifying group for feeding and heating the coloured waxes and paraffins (W), which need to be fluidified to be able to be applied onto the web-shaped material (100), and with one or more heating means (38; 58, 60, 62) capable of avoiding the cooling, and therefore the solidification, of the coloured waxes and paraffins (W) fed by the melting group before the waxes (W) themselves have been applied onto the web-shaped material (100).