Castile soap is a vegetable-based soap that is made without synthetics and without animal fat. It can be found on most DIY online retailers and is generally considered the best way to find a "pure soap" base that is still vegan-friendly. If you would rather not use castile for your hand wash, some other popular options include glycerine, or a biodegradable base like shea butter. Alternatively, you can try melting existing soap bars you may have constructed in the past. If you're interested in making your own soap bars at home, you can follow our beginner's guide as a good starting point.