Caustic soda lye
The nature of caustic soda is usually of a white powder consistency that is either in the form of flake, crystals or pearls, our caustic soda is normally pearls. The different types of forms do not change the outcome of what you are trying to do. Caustic soda can be used in a variety of applications such as soap making, frosting glass, unblocking drains, candle making and chemical experiments.
The reason caustic soda is great for unblocking drains and making soap is mainly because the caustic reacts with fat. This means that it changes the composition allowing it to dissolve the fats (in the sink or soap formula) to make soap consistency and this process is called saponification.
It is important to understand the reaction caustic soda has with water. Caustic soda is exothermic, which means that they generate heat and give off hydrogen. When you add hot water to caustic soda this process can be quite dangerous as it can cause an explosion of alkali where acid can be distributed all over the place. Instead use cold water, even though the process may take longer, it is far safer as the caustic soda is exothermic which means the hot water isn't necessary (but is still dangerous, so handle with care).