Hot-Water bottle The hot water bottle is being increasingly replaced by an electric blanket. Wendy legro thinks this is a pity, as a hot water bottle offers comfort and solace to anyone who is not feeling very well. legro changed the texture, closing mechanism, insulation and form so that the hot water bottle makes a better fit with the natural curves of the human body. her hot-Water bottle is made from felt, which spreads the warmth gradually. she impregnated the inside of the felt with polyutherane, making the bottle stronger, while rubber is used to ensure it is waterproof.