Internet Version [Naruhodo no Mori] Vol.45

by Yumiko Mori

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Vol.45   May 15th, 1999

Slime bottle

Home science experiments for mothers of elementary school children

This home-made slime bottle is made from two plastic cups. One cup is sitting on the top of another cup, and slime is moving inside these cups.

Tae: "Can I put this upside down?"
Mom: "Yes, try it!"

Tae puts the bottle upside down.
The slime flows down through a center hole into the bottom cup.
At the same time, air bubbles goes up toward the upper cup.
Big bubbles pop up from the center hole.
It is so interesting to watch the bubbles changing their shapes and the slime moving down slowly.

Tae: "This is very interesting!"
Mom: "You can enjoy playing with this toy for a long time."
Tae: "Can I make my own?"
Mom: "Yes, you can. But you should make soft slime."
Tae: "Why? Slime doesn't come down if it is too hard?."
Mom: "Well, it comes down eventually. But very slowly. I get easily irritated if it's so slow."
Tae: "Maybe you should make a slime bottle with hard slime. Then you should train yourself to become more patient."

* Some commercial version of slime bottles are sold in stores.

Materials (for one slime bottle)

Materials for making slime

borax	a teaspoonful	(You may be able to obtain from your pharmacy)
Polyvinyl alcohol (PVA)-based laundry starch	1 bottle
A glass cup		(for making saturated borax solution)
Food coloring	small amount	(You can also use watercolor paints)
A chopstick
A plastic plate		(For example, you may be able to obtain from a plastic food container.)
2 clear plastic cups		(the same size)
Scotch tape
A pair of scissors
A cutter
A marker

How to make a slime bottle

1. Place a cup upside down on a plastic plate. On the plate, mark the outer edge around the cup. Cut off the marked part from the plate.
   Make a hole (1.5-2 cm in diameter) at the center of the cut-off plate.

   

   
   <Slime making steps>

2. Make saturated borax solution.
   (Let borax melt in a half cup of lukewarm water.)

   

3. Add some food coloring to a half cup of water. The water should be colored only slightly (The colored water still needs to be transparent).
   Add approximately 1/4 cup of PVA-based laundry starch. Mix well with a pair of chopstick.

   

4. Gradually add supernatant of the saturated borax solution to the mixture while mixing.
   When about a half of the supernatant is added, the mixture should become a slime. (comparable to softness of nose snot)
   Mix it well.

   

5. Slime should occupy 80% of the cup.
   Place the plastic plate which you made at step #1 and attach the plate to the cup by taping.
   Place the other plastic cup on the cup. Put tape around the gap to seal the bottle. Then it's ready to try!

   

* You can adjust the hardness of the slime by increasing / decreasing the amount of the laundry starch.
Less amount of the laundry starch results in softer slime.

* Try making a slime bottle with two slimes with different colors. Check what happens.
Change the number of holes or the size of the hole.

* Reduce the amount of the slime by a half, then insert a pingpong ball in the bottle.
Do you think the pingpong ball is going to float?

Wonder of fluid movement

Slime making remains the most popular experiment for children. But some other people asked me "How can we use these slimes?". I didn't have a good answer. Now I have an answer, "You should make a slime bottle." Seeing the way slime is coming down in the bottle, I thought about incidental overlapping, encounter, and rule of physics. Every time I flipped the slime bottle, I saw the slime coming down in a different way. Even if two children grow up with the same parents in the same environment, the two may have different lives.