What are transparent soaps made of?

Transparent soaps are made of glycerin, and are partly soap and partly solvent. Sodium hydroxide causes crystals to form in soap, which is why the soap becomes opaque. In order to make it transparent, the soap has to be dissolved in enough solvent to make the crystals so small that light passes freely through, making the soap look transparent. There is no magic number when it comes to the quantity of solvent required. A good way to find the right quantity of solvents is to start by calculating a 60:40 soap-solvent ratio and then changing it to a 50:50 soap-solvent ratio.