Make 620
Science fun with soap, from Modern Mechanix 1938

Make a strong soap solution by mixing shaving soap and water. After taking a puff on a cigarette, blow the smoke through a bubble pipe to make a soap bubble. The inside of the bubble then will contain the white smoke, and when it breaks, it does so with a puff, furnishing a very striking experiment. A clay or corncob pipe will be more suitable than the briar variety, inasmuch as the soap mixture probably will make the pipe unsuited for further smoking.

Home Science Stunts with Soap – Link.