Don’t worry to much if you don’t have whole milk or heavy cream. Nearly any milk will work and you can substitute half-and-half for the cream. Ideally you want ingredients with a high fat content because these will create a creamy texture when cooled. Remember that we’re just experimenting here, so try what you have on hand!

Ingredients

• 1/2 cup milk (Whole or 2% work best)
• 1/2 cup heavy cream (optional)
• 1/2 teaspoon vanilla
• 1 tablespoon sugar
• 4 cups crushed ice
• 4 tablespoons salt
• 2 quart size plastic bags
• 1 gallon size plastic freezer bag
• a hand towel or gloves to keep fingers from freezing as well

Basic Directions

Begin with mixing the milk, vanilla and sugar together in one of the quart size bags. If you want, you can mix this in a bowl first so that you get all the sugar dissolved. Seal the bag tightly, you want to try to get as much of the air out of the bag as you can. Too much air left inside may force the bag open during the mixing stage.

Place this bag inside the other quart size bag, again leaving as little air inside as possible and sealing well. By double-bagging, the risk of salt and ice leaking into the ice cream is minimized.

Put the two bags inside the gallon size bag and fill the gallon sized bag with ice, then sprinkle salt on top. Again, squeeze out as much air as possible and then seal the bag. Wrap the bag in the towel or put your gloves on, and shake and massage the bag, making sure the ice surrounds the creamy mixture. Five to eight minutes should be enough time to allow the mixture to freeze into ice cream.

When you are all done carefully open the bags and extract your ice cream. Enjoy!

If you’d like to experiment a bit more you can try substituting a mixture of heavy cream and your choice of milk. Mix up a few different batches and compare the texture of ice cream. Which to you think will have a smoother texture?

We suggest using freezer bags because they are thicker and less likely to develop small holes, allowing the bags to leak. You can get away with using regular plastic bags for the smaller quart sizes, because you are double-bagging. If you plan to do this indoors, we strongly recommend using gallon size freezer bags.

What does the salt do?

Salt forces the ice surrounding the bag of ingredients to melt. This “brine” solution or liquid that forms in the gallon bag absorbs the heat from the ice cream mix and gradually lowers the temperature of the mix until it begins to freeze.

If there were no salt added to the ice, it would melt at 32 degrees Fahrenheit and eventually the ice water and mix would come to equilibrium at 32 degrees. The ice cream mix, however, does not begin to freeze until its temperature falls below 27 degrees. Therefore, in order to freeze the mix, we need to add salt to the ice to lower the freezing temperature.

With 4 tablespoons of salt mixed with our ice, the brine temperature should remain constant at around 8 to 12 degrees Fahrenheit. This will give the rapid cooling and freezing that is essential to making smooth creamy ice cream.

What to do:

1. Mix 1 cup hot water and 1.5 tsp. of Borax until dissolved. Set aside.
2. Mix 2 cups of clear glue and 2 cups of warm water together in a plastic bowl.
3. Using a metal spoon, slowly pour Borax mixture into the glue mixture while stirring quickly. Stir until the mixture leaves the side of the bowl. Slime will be sticky. Knead the mixture until it is no longer sticky. The more you work with it the easier it will become.

What’s the science?

Slime is an excellent example of a polymer. Polymers are large molecules consisting of repeating identical structural units connected by covalent chemical bonds. Polymers can be naturally occurring or manmade. Manmade polymers are materials like nylon, polyester, and polystyrene. Examples of naturally occurring polymers are proteins in our body like tubulin and actin. These proteins make up microtubules and microfilaments that serve as structural components within our cells.

Storage and Safety Guidelines:
Store Slime in an airtight container for about 3 weeks of use. Slime is non-edible. When you are through with it, discard in a trash container. Do not wash down the drain.

More about Slime:

Slime is a polymer. Polymer is a term used to describe anything that consists of repeating identical structural units. It basically is like a long strand of spaghetti and the long chains flow past each other with ease. They can be naturally occurring or man-made (synthetic). Examples of polymers include plastics, starches, sodium polyacrylate, nylon and many more. Slime is also considered to be a non-Newtonian Fluid, basically a fluid that has special properties.

You should answer the following questions when exploring the properties of slime (a.k.a. playing with the cool stuff). Make sure your record your observations and post them in the comment box below. Try and do this before you read the rest of the article.

1. Describe how the slime reacts when you pull it apart with a quick forceful motion?
2. Describe how the slime reacts when you let it drip between your fingers?
3. Can you form a ball? What happens when you drop it on the table?
4. Do other fluids (like water, or ketchup) act the same way?

History of Slime:

Slime as a toy dates back to the 1920′s, when chemist Hermann Staudinger was researching polymers. He was the first one to try and make long cross-linked chains of the molecules instead of circles. This allowed the polymer to be slippery and gooey. By the 1930′s other scientists used his polymer model and synthetic polymers began to be studied and created. But it wasn’t until the 1980′s that slime began to be sold in stores as a toy for children. Ever since then you can’t step into a toy store without seeing the gooey, oozy stuff on the shelves. The slime you find in the store and the slime you can make with this recipe are both non-Newtonian fluids. Did you try to make it and answer the questions about its properties? If so, read on to find out about non-Newtonian fluids.

What does non-Newtonian mean?

All fluids have a property known as viscosity that describes how the fluid flows – commonly thought of as how thick or thin a fluid is. For instance, honey is much more viscous than water. When a fluid’s viscosity is constant it is referred to as a Newtonian fluid. Slime is an example of a fluid whose viscosity is not constant, it changes depending on the stress or forces applied to it. If you pull it apart real hard and apply a large force, it becomes very viscous and will break in half. If you gently pour it, applying little force, it will flow like honey or molasses. This kind of fluid is called a dilatant material or a shear thickening fluid. It becomes more viscous when agitated or compressed.

Another non-Newtonian liquid is ketchup. Ketchup behaves in just the opposite way from Slime. It becomes less viscous when agitated. Liquids like this are called thixotropic. If you leave a bottle of Ketchup on a shelf, it becomes thicker or more viscous. Nearly everyone has experienced this while trying to pour the liquid from a new bottle – it refuses to move. If you shake the bottle or stir it up it becomes less viscous and pours easily. Another example of a non-Newtonian fluid is Oobleck, one of our other great activities.

Is the slime in the store made using this recipe?

Most commercially sold slime is made using polyvinyl alcohol (PVA), a non-toxic substance that gives slime its texture. PVA still needs to be mixed with borax to get the final slime product. The borax is a gelling agent that cross links the PVA molecules together to form the slime. Borax does the same thing with the glue in this recipe. You can find Borax in the laundry detergent aisle in your grocery store. It is an inexpensive laundry booster and has lots of great household uses.

Other sources about slime:

There are some fun books that discuss animals in nature that produce their own slime, science experiments and other fun facts. You can find these and many other books at your local library.

• The Book of Slime by Ellen Jackson
• Lotions, Potions and Slime: Mudpies and More! by Nancy Blakey
• Oobleck, Slime & Dancing Spaghetti: Twenty Terrific at Home Science Experiments Inspired by Favorite Children’s Books by Jennifer Williams

Make sure you try this at home and don’t forget to come back and write a comment about how it went.

• Box of Toothpicks
• Bag of Gumdrops

What to do:

1. Use gumdrops to connect 5 toothpicks in a ring. This is your base.
2. Use 2 toothpicks and 1 gumdrop to make a triangle on one side of the base.
3. Repeat all the way around the base until you have 5 triangles.
4. Use toothpicks to connect the gumdrops at the tops of the triangles. Now how many triangles do you have?
5. Push 1 toothpick into each of the top gumdrops.
6. Use one last gumdrop to connect these toothpicks at the top.

What’s the science?
Engineers often use triangles when they design buildings. Did you notice that your dome is made up of lots of triangles? That’s because triangles are stable shapes. That means they don’t bend, twist, or collapse easily when you push on them. A square is not as stable as a triangle. Test it. Make a square and a triangle out of toothpicks and gumdrops.  Press down on one corner of each shape. How do the two shapes compare? Does one bend, twist or collapse more easily than the other?

What will happen if . . .

• you make a base with six sides instead of five sides?
• you build squares rather than triangles on top of the base?

Choose one thing to change (that’s the variable), and predict what you think will happen, then test it.

Film canister rockets are always pretty amazing considering all that powers them is a little bit of Alka-seltzer and water. The launching time is always a bit unpredictable and that just adds to the fun.

What you need:

• Paper, Index cards or cardstock,
• Translucent film canister, Tape,
• Scissors, Effervescing antacid tablet,
• Water and Paper towels

What to do:

1. Wrap and tape a tube of paper around the film canister. The lid of the canister goes down.
2. Cut fins from the index cards and tape to the rocket.
3. Make a nose cone by cutting a circle out of paper. Cut out a pie shape from the circle and twist the paper into a cone. Tape the cone together. Then tape it on the open end of the paper tube.
4. Turn the rocket upside down and fill the canister 1/3 full with water.
5. Work quickly! Drop in a 1/2 tablet and snap the lid on tight.
6. Stand the rocket upright and stand back!

CAUTION: Be careful when launching your rocket. Stand back and don’t point it at anyone.

What’s the science?
As the antacid tablet “fizzes” carbon dioxide inside the canister, pressure from the gas builds and eventually pops the lid off. The amount of force, or push, created is related to the amount and speed of gas and water propelled from the canister.

What will happen if…

• you change the design of your rocket?
• you use more or less “fuel?”
• you use hot or cold water?

Choose one thing to change (that’s the variable), then predict what you think will  happen and test it.