Hotfix Elements have a coating of hot-melt glue on the reverse side of Flat Back stones. This is activated by heat at temperatures between 120C-170C (248F-338F) and bonds with the carrier material. The glue hardens as it cools and the elements are securely and permanently fixed (generally after 24h). This unique Swarovski Hotfix glue is easy to clean and is machine-washable.