The can contains water (~80%), butane gas (~17%), surfactant (~1%), and other ingredients including vegetable oil (~2%).[2] The liquefied butane expands when the product is ejected from the can. The butane evaporates instantly, forming bubbles of gas in the water/surfactant mixture. The surfactant(s) cause the bubbles to have stability and hence a gas-in-liquid colloid (foam) forms. The bubbles eventually collapse and the foam disappears, leaving only water and surfactant residue on the ground. The US patent application can be viewed here