Water Jelly Crystals

Amazing hydrogels - polymers that are saving the environment.

Water Jelly Crystals are an example of amazing hydrogels… superabsorbent polymers that are saving the environment. Superabsorbent polymers are rapidly becoming one of the most exciting environmental education topics in classrooms worldwide.

Today, superabsorbent polymers are widely used in such applications as forestry, gardening, and landscaping as a means of conserving water. Imagine using a substance that could store water in the soil and then release it as the plant’s roots need it. While we may consider water-absorbing polymers to be a modern convenience, imagine the impact that such technology is having on parts of the world that are plagued by drought. 

Experiment Materials

  • Water Jelly Crystals(available in a variety of colors and quantities)
  • Tap water
  • Quart size resealable zipper-lock bags
  • Food coloring
  • Distilled water
  • Other liquids: tomato juice, orange juice, milk, vegetable oil, soda, hot water, salt water, or melted snow
  • Pot for growing plants
  • Plant seeds (beans, radishes, lettuce, flowers, etc)


Water Jelly Crystals (cross-linked polyacrylamide copolymer gel) are generally considered not to be a health hazard. They’re non-toxic, safe for use around pets and young children, and are considered to be environmentally beneficial. Do not taste or eat any of the materials described in these activities. Since these crystals are designed to be used with plants, bury them in a planter box or garden when you’re finished using them. Throwing them away is such a waste. In reality, you have a reusable, lifetime supply. Consult our safety section for additional information.

  1. Place 1 teaspoon of Water Jelly Crystals in a quart size zipper-lock bag and add 8 ounces of tap water. Add 1 or 2 drops of food coloring to the water to make the experiment more colorful. Seal the bag and observe what happens to the crystals after 10 minutes, 30 minutes, and 1 hour. How has the polymer changed? Will the crystals get any bigger if you add more water?
  2. Those tiny, pebble-like chunks grabbed onto water molecules and exploded into lots and lots of fat, globby, water-filled crystals! Go ahead and touch those squishy, gooey, slimy, shimmery lumps! If you’ve let the crystals soak at least an hour, most of the water will have been absorbed. The longer you leave them, the more likely you are to have little or no water remaining.
  3. Repeat the previous experiment, but this time try distilled water in place of regular tap water. Distilled water is similar to rainwater, so the experiment will show how much rainwater the crystals will absorb in the ground.
  4. Pour off any excess water that’s in the plastic cup, but let the crystals in the bag soak up water. Stick your hand into the resealable bag full of Water Jelly Crystals. It’s a most interesting sensation. You may think it’s cold and slimy but leave your hand in the bag for a moment and do some “research.” Remove 3 or 4 crystals and put them on the table. Use a ruler to measure their size. What differences do you see? Compare one of the hydrated crystals (soaked in water) to a crystal that did not soak in water. How do the sizes of the water-filled crystals compare to each other? What about the dry crystals? 
  5. Will the polymer crystals absorb anything other than water? Try any of these liquids in place of water: tomato juice, orange juice, vegetable oil, milk, soda pop, rainwater or melted snow, hot water, or salt water. What did you discover?

Cold Crystals – Place a zipper-lock bag of the jelly-like polymer crystals in the freezer. Examine the bag of polymer after 12 hours. Compare the length of time that the crystals stay cold with a similar amount of ice in a zipper-lock bag. Research shows that the polymer crystals hold the cold 2.5 times longer than ordinary ice. Could you use polymer crystals in place of crushed ice the next time you need an ice bag?

Polymer Plants – Grow grass seed, radishes, beans, or other fast-starting plants in a mixture of polymer and soil. The soil/polymer mixture should be half soil and half polymer crystals that have already absorbed water. Try growing the same seeds that you planted in the soil/polymer mixture in just plain soil and compare the growth at two day intervals for one or two weeks. Growing a polymer plant makes a great science fair project! Will radish seeds grow in a cup of polymer crystals without soil? Try it — you might be surprised!

Additional Info

How much polymer should I use with my lawn and garden? Use the following suggestions as a starting point…

  • One pound of Water Jelly Crystals will absorb up to 35 gallons of rainwater or snowmelt, and 20-25 gallons of tap water, depending on the salt content of the water.
  • Water Jelly Crystals can be applied wet or dry. Dry granules are usually easier to use, but soak them thoroughly to fully fill them with water (hydrate). When hydrated, the granules look like chunks of clear gelatin about 1/2 inch in diameter.
  • Dry Application: For large quantities of potting soil or backfill around trees and shrubs. – 1.5-2 pounds/ cubic yard of potting soil or backfill – 1 ounce/ cubic foot of soil
  • For small quantities of potting soil – 1/2 teaspoon per quart of soil. Note: Since dry granules swell to many times their original size when water is added, 15-20% swelling room must be left in each planting hole or flower pot to compensate.
  • Wet Application: Best for small applications such as repotting house plants and planting shrubs, small trees, and bedding plants. 1/2 teaspoon of dry granules absorbs approximately 1 cup of water. – 1 ounce of dry granules absorbs approximately 1 1/2 cups of water. – 1 pound of dry granules absorbs approximately 30 gallons of water. Mix the granules in water and allow the mixture to stand for 60-90 minutes (Hot water works faster). Once you have the polymer all soaked up, the application rate is roughly one part hydrated polymer to four parts soil.
  • House/Office Plants – 6″ pot (2/3 gallon) 1 teaspoon dry or 2 cups hydrated – 8″ pot (1 1/2 gallons) 2 Tablespoons dry or 6 cups hydrated – 5 gallon pot 7 teaspoons dry or 1 gallon hydrated Note: Mix Water Jelly Crystals in the lower half of the pot, because the water tends to flow quickly through porous potting soil, before the granules near the top have time to rehydrate fully.
  • Repotting: Using the above rates mix granules or hydrated gel (the hydrated gel works the best) thoroughly in the lower half of the pot. If using dry granules, fill the soil only to within 1 inch of the pot rim to prevent swelling out of the pot.
  • Existing Plants: Depending on the container size, use a pencil or wooden spoon handle to poke 4-6 holes around the plant, going to the bottom, Divide the correct amount of dry granules evenly among the holes, pushing them to the bottom. Water the plant slowly to hydrate the granules. Wait at least 2-3 weeks before changing watering intervals, to give feeder roots a chance to grow down into the granules.
  • Vegetable and Flower Gardens: Use 4-5 pounds/ 100 square feet for low-water adapted flowers, and up to 10 pounds/100 square feet for water loving vegetable and flowers. Hint: The addition of weed-barrier fabric will further reduce the need for water or weeding. Application suggestions… By hand, or using a spreader, distribute the granules evenly over the leveled bed, and then turn the soil back under. Bedding plants may be given a quick start by mixing a handful of hydrated gel in the back fill of each plant, taking care not to leave clumps of gel. Water the bed thoroughly after planting.
  • Trees and Shrubs: Dig a hole 5 times the diameter, but no deeper than the root ball or container. The table shows the amount of dry granules needed to mix in the backfill of round holes 2.5 to 5 times the diameter of the container. Container Size 2.5 times 5 times – 1 gallon 1/3 cup 1/2 cup – 5 gallon 5/8 cup 3 1/2 cups – 15 gallon 1 2/3 cup 7 3/4 cups. If you don’t want to dig such a big hole just calculate the amount of backfill and figure one once per cubic foot. The bigger the hole the more polymer you can use and the more water storage you’ll gain.
  • New or Seeded Turf: Watering intervals can be extended approximately one day for each 7 1/2 pounds of Water Jelly Crystals per 1000 square feet given evaporation rates of .25 inch per day. For example, 15 pounds of granules normally stores 1/2 inch of extra water (two additional days between waterings) and 30 pounds stores 1 inch of water (four additional days between watering). Warning: To avoid making a soft lawn, never use more than 5 pounds of Water Jelly Crystals per tilled inch per 1000 square feet. Thus, 20 pounds must be tilled in 4 inches; 30 pounds 6 inches. Increase the application rate roughly 10% over sloped areas. Save one pound to spread over the top of each 1000 square feet before laying sod (but not if you are seeding, as it just breaks down in the wet phase if not covered by soil.) Water thoroughly and slowly. Application: By hand, or using a spreader, distribute the granules evenly before roto-tilling to the appropriate depth.