Butyrolactonethiol (SPIERA) is a perm and straight perm agent with mild acidity and superior performance developed by the proprietary technology of Showa Denko. SPIERA has been developed as an efficient perm agent that does not damage hair.
L-cysteine is natural amino acid found in human hair at a high content. One of its major applications is permanent wave solution. DL-cysteine, a synthetic product, can be used as permanent wave solution and is much superior to L-cysteine in minimizing the roughness.