I don't think it's as strong as caustic soda but chinese supermarkets sometimes have lye water, which might do. Also this article describes heating regular sodium bicarb to make stronger "baked soda", I've never done it though - http://www.nytimes.com/2010/09/15/dining/15curious.html
I don't think it's as strong as caustic soda but chinese supermarkets sometimes have lye water, which might do. Also this article describes heating regular sodium bicarb to make stronger "baked soda", I've never done it though - http://www.nytimes.com/2010/09/15/dining/15curious.html