Educator How-To: Recycled Plastic Shrinky Dinks

The beginning of the school year is an exciting time for teachers and students alike. We have a quick science activity here that will engage  new students and make your room too cool appropriately cool for school: Shrinky Dinks.

Educator How-To: Recycled Plastic Shrinky Dinks

There are myriad of ways you can use this activity, so the application is up to you, but I am envisioning name plates or name tags, zipper pulls for pencil bags, cubby or tote markers, key chain fobs … the possibilities are endless!

Materials:

No. 6 plastic
Sharpies, colored pencils, or an inkjet printer
Sandpaper
Scissors
Oven or toaster oven
Parchment paper
Non-insulated baking sheet or flat piece of cardboard
Hole punch

Procedure:

The first thing you need to do for this project is to gather is No. 6 plastic, also known as polystyrene. Polystyrene is hard and clear and often used in protective packaging like deli containers. While it can be tricky to recycle, recycled polystyrene can be used in manufacturing rulers, license plate frames, vents, switch boards, and thermal insulation items. Oddly enough, No. 6 plastic can also be whipped into a foam and made into Styrofoam.

For this example, I saved a bunch of lids from aluminum takeout containers, but you can use just about anything that is rated No. 6.  If you want to make an image that will shrink evenly, you will need a piece of plastic that has been stretched evenly. Corners, cups and edges can be unpredictable because they are stretched and molded in multiple directions.

“Plastics are made of long chain-like molecules called polymers. Because polymer chains are so long, they can be manipulated to create a wide-range of properties — in this case for No. 6 plastic, polystyrene. Polystyrene is a thermoplastic, meaning the long polymer chains are heated and stretched, then cooled to form the plastic sheet. The polystyrene remains in this “stretched out” state unless something causes it to change. The cool thing about thermoplastics is that upon reheating the plastic, it reverts to its original state, in other words, it shrinks. This is the same process used to “shrink wrap” items like food containers or other products that have protective plastic wraps.” Lori Steward, Middle School Science

I decided to try something different this time, so I cut the unpredictable edges off my plastic lid in order to get a flat piece of plastic I could trim and run through the printer.

Educator How-To: Recycled Plastic Shrinky Dinks

(If you decide to use sharpies in your project, you can give your students a piece of plastic and a set of sharpies and let them get to work. The sharpie will adhere to the plastic with no problems. If you want to use colored pencils or an ink jet printer, you will need to scuff up your plastic so that there is a bit of texture for the color to stick.)

Educator How-To: Recycled Plastic Shrinky Dinks

I knew I wanted to cut around the outline of my long-horned beetle, but for students you might want a standard shape like rectangles for name tags or zipper pulls. You might also consider using a die cut to make a particular shape — like circles or the school mascot.

If you want to attach a cord or a ring to your shrink dink, you MUST punch a hole in it BEFORE you bake. The standard sized hole punch shrinks considerably.  I always have the urge to use a smaller hole punch, but then I can’t fit anything through the remaining hole.

Educator How-To: Recycled Plastic Shrinky Dinks

Before baking.The larger hole is a standard sized hole punch. The smaller hole is a mini punch.

SO! After I ran the plastic through the printer, I trimmed around my shapes. The “painted lady” was easy as it was a rectangle, but the beetle was trickier.  Since No. 6 plastic is pretty thin and brittle, corners are delicate. You can see in the picture that I had a bit of a problem around the beetle’s tarsal claws. No worries though; the plastic gets tougher as it shrinks.

Educator How-To: Recycled Plastic Shrinky Dinks

Now get out your baking sheet. I like putting a piece of parchment paper down on the baking sheet to protect the surface that you might otherwise put cookies on, but it isn’t totally necessary. If you do decide to use parchment paper, it has a tendency to curl, so you may need to wad up the paper and flatten it back out before using it.

Place your decorated plastic on the cookie sheet and place the sheet in the oven to bake the plastic for 2- 3 minutes on 325 to 350 degrees. Each oven is different, so watch closely!

Danger Note: You are already working with heat, but you might also be working with a possible human carcinogen. No. 6 plastic has been found to leach styrene, so if you choose to do this craft make sure it is in a well-ventilated area!

You will see the plastic curl up and then flatten back out. Wait about 30 seconds longer than you think you need to. Then wait a few more. It is extremely tempting to take the shrink dinks out before they are totally ready, but waiting longer than necessary doesn’t really hurt anything. So resist!

Occasionally your shrinky will decide to stick in a single spot. Not to worry! When you pull the items out of the oven, immediately use something hard and flat, like the bottom of a pie pan, to press out any uneven spots. If you aren’t quite satisfied, you can actually stick your shrunken piece back in the oven and reheat it until it is soft.

Once you remove the piece from the oven, it cools very quickly, so you can handle it almost instantly. I usually pull the cookie sheet out, flip the piece on the kitchen counter and press it flat for a few seconds. By the time I have done all of this, 30 seconds or so, the piece is ready to hold.

How much shrink can a shrink dink shrink? About this much.

Educator How-To: Recycled Plastic Shrinky Dinks

The image on the left is the starting size and the image on the right is the finished size.

Final product!

Educator How-To: Recycled Plastic Shrinky Dinks

How To: Make Terra Cotta Armor!

Check out the previous post The Clothes Make the Warrior to learn how to decipher the armor on the Terra Cotta Warriors now on display at HMNS. Then, try your hand at making your own!

Materials:
Large paper grocery sack
Scissors
Cardboard
Hole-punch
Brads
Tape
Paint (optional)

Procedure:
armor1. Cut 150 squares out of cardboard.  The squares should be 1.75 x 1.75 inches a piece.  You may cut one and use it as a template to trace the rest. 
2. Cut the paper bag into a tunic shape that can be slipped over the head.  You may have to experiment and find out what works best depending on the size of the child.
3. Cut out two rectangular pieces (you can use the left over pieces from making the tunic) and tape them to the shoulders.  These will be the guards. 
4. If you wish to paint your armor, you should do this prior to assembly.  I do not recommend painting the bag, but you can paint the square pieces.
5. Use the hole-punch to punch a hole in the top-middle of each square.
6. Starting at the top of your tunic, attach the squares one at a time by placing a brad through the pre-punched hole and then poking it through the bag.  Make sure to put the squares close together.
7. Continue this process until you have the front and back completely covered.  You may have to trim some of the squares to make them fit properly.
8. Next move onto the guards.  These are the rectangular pieces attached to the shoulders of the tunic.  Attach the squares to the guards in the same manner.  You may need a sharp object to start the holes in this area.  This should be done by an adult.
9. Slip the armor on your favorite child and have them stand sentinel!

Kneeling Archer_resized

Background:
Armor was made of small plates of leather, covered in lacquer to stiffen them.  On the top and bottom of each plate are double close-set-holes.  These plates were attached by knots of leather or thong.  Depending on the size of plates, a suit of armor could have up to 250 plates.  The smaller the size of the plates, the higher the rank of soldier.  The armor of higher ranking soldiers had more decorative straps and ribbons in a geometric pattern.  The armor opened up on the right side allowing it to be slid over the head.

Heavy infantry and low ranking soldier’s armor covered the front of the torso from shoulder to waist, curving in the front.  In the back, armor went from the shoulders to the lower back.  Attached at the shoulders were shoulder and upper guards.  To allow for movement, plates at the waist and shoulder guards were loosely sewn.  This armor would be made from larger leather plates and would have no straps or ribbons for decoration.