Bubble guns typically use a liquid solution made from a combination of water, soap, and glycerin. This mixture creates a solution ideal for forming bubbles when expelled from the bubble gun. The soap helps to reduce the surface tension of water, allowing the solution to stretch into bubble shapes without breaking easily. Glycerin is added to the mixture to enhance the viscosity and elasticity of the bubbles, making them more durable and long-lasting. This solution is non-toxic and safe for children, making it perfect for bubble guns, which are often used as toys.