The surfaces of polydimethylsiloxane (PDMS) RTV rubber display macroscopic and microscopic (as detected in the atomic force microscope) morphological changes, when heated to 250-280-degrees-C, in the presence of air. The separation between adjoining PDMS film surfaces disappears in the same temperature range and the film pieces are effectively soldered, as verified by scanning electron microscopy and by mechanical testing. Mechanical failure of films joined by soldering is cohesive or interfacial, depending on the extent of film ageing, during film preparation. These results are interpreted by considering that PDMS network chains undergo scission, at the above temperatures. As a result, reactive chain segments can migrate at the rubber surface and across the rubber-rubber interface; their recombination forms a new network, from two adjacent networks.