My 8-YO loves Orbeez, those water-thirsty polymer balls that go from the size of cookie sprinkles to the size of marbles after a quick soak.
I wondered whether we could make something similar from gelatin or agar.
A quick search online showed me that some chefs use a technique called oil spherification to make tiny round morsels using everything from balsamic vinegar to fruit juice, mixed with gelatin and agar. It’s known to cooks as a “molecular gastronomy” technique, and takes advantage of the fact that water and oil don’t mix. Water-based droplets falling through chilled oil form into perfect spheres due to surface tension, and gelatin and agar added to the mix are colloids that solidify as they cool.
We made some fun (inedible) orbs of our own, using the technique: standard orbs (from gelatin or agar and water), floating orbs (with agar and vinegar) and color-changing acid/base indicator orbs (from red cabbage juice and gelatin or agar.) Adult supervision is required for this project, since it involves hot liquids. The orbs may also be a choking hazard, so keep them away from toddlers. I demonstrated how to make them on Kare11 Sunrise News.
To make magic orbs, you’ll need
-unflavored gelatin or agar*
-cold vegetable oil in a tall container. Chill oil in freezer or on ice for at least an hour, or until it is cloudy, but still liquid.
HINT: Orbs made with vinegar and agar shrink better than those made with gelatin (see floating orb recipe below!)
Standard colored orbs:
1. With adult supervision, dissolve 5 packets unflavored gelatin or 2 Tbs. agar in 1 cup hot water. Add 2 tsp. vinegar. Microwave and stir until completely dissolved.
2. Pour into smaller containers and add food coloring. When cooler, but not solid, add the melted, colored gelatin or agar to an empty glue container or squeeze bottle.
3. Drip gelatin or agar solution into the cold oil, a few drops at a time so it forms into marble-sized orbs and sinks. Drip two colors together to make multi-colored orbs! Allow to cool for 30 seconds or so and retrieve with a slotted spoon or strainer. Rinse with water and repeat, re-chilling the oil as needed until you have as many orbs as you want.
4. Rinse orbs with water. Dry them out by setting them on a plate overnight if you want to see them shrink and then re-hydrate them with water. Orbs can be kept in a plastic bag in the refrigerator. (Keep away from small children, since they may be a choking hazard.)
To make floating orbs, follow directions above, but make with 1 cup white vinegar and 2 Tbs. agar. They will sink and float when added to water with a few tsp. of baking soda mixed in as the vinegar and baking soda react to form carbon dioxide gas.
To make color-changing orbs, dissolve 2 Tbs. agar or 5 packs unflavored gelatin in 1 cup red cabbage juice (magic potion) and follow directions for making orbs. Then drop them in vinegar to watch them turn pink or in water containing baking soda to watch them turn blue!
Could you make homemade jelly beans using flavored gelatin using this same method? Try it!
*Agar, or agar agar flakes can be found in the Asian food section of many grocery stores!
What happens when food coloring molecules move, or DIFFUSE through gelatin, the substance that makes jello jiggle?
This creative science experiment that my kids and I invented lets you play with floatation physics by sprinkling glitter on melted gelatin, watch colorful dyes diffuse to create patterns and then use cookie cutters to punch out sticky window decorations. Water will evaporate from the gelatin, leaving you with paper-thin “stained glass” shapes.
You can watch us making them on Kare11 Sunrise News by clicking here.
-plain, unflavored gelatin from the grocery store or Target
–a drinking straw
*You can use the recipe below for two pans around 8×12 inches, or use large, rimmed cookie sheets for your gelatin. For a single pan, cut the recipe in half.
Step 1. Add 6 packs of plain, unflavored gelatin (1 oz or 28 gm) to 4 cups of boiling water. Stir well until all the gelatin has dissolved and remove bubbles with a spoon.
Step 2. Allow gelatin to cool to a kid-safe temperature. Pour the liquid gelatin into two large pans so it’s around 1-1.5 cm deep. It doesn’t have to be exact.
Step 5. In the pan with no glitter, use a straw to create holes in the gelatin, a few cm apart, scattered across the surface. It works best to poke a straw straight into the gelatin, but not all the way to the bottom. Spin the straw and remove it. Then, use a toothpick or skewer to pull out the gelatin plug you’ve created. This will leave a perfect hole for the food coloring. Very young children may need help.
Step 6. Add a drop of food coloring to each hole in the gelatin.
Step 7. Let the gelatin pans sit for 24 hours. Every so often, use a ruler to measure the circle of food coloring molecules as they diffuse (move) into the gelatin around them (read about diffusion at the bottom of this post.) How many cm per hour is the color diffusing? Do some colors diffuse faster than others? If you put one pan in the refrigerator and an identical one at room temperature, does the food coloring diffuse at the same rate?
Step 8. When the food coloring has made colorful circles in the gelatin, use cookie cutters to cut shapes from both pans of gelatin (glitter and food coloring), carefully remove them from the pan with a spatula or your fingers, and use them to decorate a window. (Ask a parent first, since some glitter may find its way to the floor!) Don’t get frustrated if they break, since you can stick them back together on the window.
Step 9. Observe your window jellies each day to see what happens when the water evaporates from the gelatin.
When they’re dry, peel them off the window. Are they thinner than when you started? Why? Can you re-hydrate them by soaking the dried shapes in water?
The Science Behind the Fun:
Imagine half a box filled with red balls and the other half filled with yellow ones. If you set the box on something that vibrates, the balls will move around randomly, until the red and yellow balls are evenly mixed up.
Scientists call this process, when molecules move from areas of high concentration, where there are lots of other similar molecules, to areas of low concentration, where there are fewer similar molecules DIFFUSION. When the molecules are evenly spread throughout the space, it is called EQUILIBRIUM.
Lots of things can affect how fast molecules diffuse, including temperature. When molecules are heated up, they vibrate faster and move around faster, which helps them reach equilibrium more quickly than they would if it were cold. Diffusion takes place in gases like air, liquids like water, and even solids (semiconductors for computers are made by diffusing elements into one another.)
Think about the way pollutants move from one place to another through air, water and even soil. Or consider how bacteria are able to take up the substances they need to thrive. Your body has to transfer oxygen, carbon dioxide and water by processes involving diffusion as well.
Why does glitter float on gelatin? An object’s density and it’s shape help determine its buoyancy, or whether it will float or sink. Density is an object’s mass (loosely defined as its weight) divided by its volume (how much space it takes up.) A famous scientist named Archimedes discovered that any floating object displaces its own weight of fluid. Boats have to be designed in shapes that will displace, or push, at least as much water as they weigh in order to float.
For example, a 100 pound block of metal won’t move much water out of the way, and sinks fast since it’s denser than water. However , a 100 pound block of metal reshaped into a boat pushes more water out of the way and will float if you design it well!
What is the shape of your glitter? Does it float or sink in the gelatin?
Here’s a video I made for KidScience app that demonstrates how to make window gellies
Credit: My 11 YO daughter came up with the brilliant idea to stick this experiment on windows. I was just going to dry out the gelatin shapes to make ornaments. Kids are often way more creative than adults!