Our rain boots are made from high quality all-natural rubber. The cotton-lining is slid onto the boot-tree and the natural rubber is fitted to the pattern in sections. The boot is then baked in the vulcanisation tank for an hour at 140C. For this reason, all our linings are 100 per cent cotton, any artificial materials would simply melt during the baking process. Once the boots have cooled down, every pair is tested by hand to ensure it is completely waterproof. Chelsea Boots - Green