About the ingredients: Solid Bubble Bath

Sodium Lauryl Sulfoacetate (AKA SLSa)
Sodium lauryl sulfoacetate (SLSa) is a safe, skin friendly and surfactant derived from coconut and palm oils. It makes large bubbles and creates a rich lather when combined with water. It is NOT the same as Sodium Lauryl Sulfate (AKA SLS).
Cream of Tartar
Cream of tartar is a fine powder that is a byproduct of making wine. It is commonly found in the spice aisle and is food safe.
Vegetable Glycerin
 Vegetable Glycerin is a clear liquid typically made from soybean, coconut or palm oils. It is also a humectant, which meals it pulls water into the outer layer of your skin from deeper levels of your skin and the air.
Sodium Bicarbonate
Sodium Bicarbonate is commonly known as baking soda. 
Castor Oil
Castor oil is a vegetable oil that is made from the seeds of the castor plant.