Science, Tech, Math › Science Easy Alum Crystal Growing Project Share Flipboard Email Print Ude/Wikimedia Commons/CC BY-SA 3.0 Science Chemistry Activities for Kids Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated March 10, 2019 Are you looking for an easy, safe, reliable crystal-growing project? These alum crystals may be the easiest crystals you can grow. Why This Project Rocks Non-toxic crystal (alum is a spice)Uses hot tap water, not boiling waterEasy to do—mix and waitExtremely reliable results—crystals will growOnly requires a few hours for good crystal growthResults in crystals large enough to pick up and examine Grow Easy Alum Crystal To grow these crystals you will need: 1/2 cup hot tap water2 1/2 tablespoons alum Simply stir the alum into the water and wait for crystals to grow. Alum crystals usually are visible within a half an hour and reach a good size within a few hours. It's that easy! When the crystals are to your liking, use a fingernail to scrape them off the side of your container. You can examine them and keep them.