Know anyone with a strange phobia of garbage bags? You will soon with your easily makeable, quickly inflatable, highly sensational Bag Monster. This project is inspired by a beautiful idea by artist Joshua Allen Harris where he made three dimensional creatures out of trash bags that inflate with the passing of the NYC subway.

My students (and I) love all things that inflate: bouncy castles, balloons, wacky waving inflatable flailing arm tube people, and more. So this project was a way to tie our passion for all things air-filled with geometry, sewing patterns, design, and making three dimensional objects.

What: Bag Monsters!
Why: Raaaawwwwr!
Concepts: design, geometry, pressure, spatial thinking
Time: ~ 50 minutes minimum (multi-day better)
Cost: ~ $0.20 per monster
Materials:
- Garbage bags (mix of colors is great)
- Masking Tape
- Plastic bottle (can substitute cardboard tubes)
- Blowdryer with cool setting (or other way to shoot air)
Tools:
- Scissors
- Pen and paper
- Measuring tape or Ruler (optional)

Let's monster.

Step 1: Design Your Beast

Your beast can be a beauty or downright barbarous, but either way, give it some thought first.

Bag Monsters (at their most basic) are made with an identical front and back. They are taped along the seams with a hole to let in air. They can also have other holes to release air if your bag monster pressure gets to high. Often it is easiest to cut a main body, and add on limbs.

For some thoughts on variations and challenges in design, check out the last step.

Step 2: Build a Body

Bag Monsters are made, not born.

Start with marking and cutting out the main body. The easiest way to do this is lay a plastic bag down flat, and cut out two identical patterns, one on top of the other.

To join them together, use masking tape along the seams. It's okay if you don't do it perfectly, and actually good if there are little holes for the air to escape. Leave room for any extra limbs, spikes, horns, etc. you want to add on later.

Step 3: Make Limbs and Add-Ons

Give your bag monster a hand. Or two. And some horns.

Make limbs and fun add-ons by cutting out more pieces of plastic. For doing detailed corners and curves, a good trick is to layer masking tape on top and below, and then cut out the shapes with a little tape margin left over.

When attaching limbs, spikes, horns, etc. to the main body, cut a hole in the main body before taping on so that air can easily pass through.

Step 4: Give It Personality

Sure they're called bag monsters, but some of them are actually great when you get to know them.

Is your bag monster, pensive, angry, sad, loyal, hungry, incapable of being put in an emotional box? Give it some details and decorations to either connote warm fluffy feelings or to inspire utter fear in the hearts of neighbors.

At the most basic, you can use masking tape to make faces with pens to draw on. Get creative, and use things you have around to make it unique.

Step 5: Prepare to Inflate

Your monster is almost ready to haunt! It just needs a little air.

Cut a water bottle or cardboard tube that can fit easily around whatever you're using to blow air. Tape it in to some part of your bag monster, so it can inflate easily when placed over your air-pusher.

I'm using a blowdryer in this example, but vacuum cleaners in reverse, shop-vacs, and dustbusters all work great, too.

TIP: If you're using a blowdryer, use one that has a cool setting. In a classroom, I tape down the "cool setting" button to make sure it only blows cold air. Otherwise, you'll end up with hot hands and melty monsters. :)

Step 6: Bring Your Monster to Life!

You don't even have to wait for a lightning storm. Just stick the blowdryer in and inflate! Your bag monster will spring to life, and begin it's happy haunting. Once you've made one, there's plenty to do, change, or inspiration to make more, so keep going!

Here are some variations and things to think about especially in an educational setting:

Measure: use this project to measure surface area, and approximate volume of creatures
Movement: can you make a bag monster that moves (like a flailing inflatable arm tube person)
Geometry: can you make specific three dimensional shapes?
Extremes: make the longest, the tallest, the most volume, the heaviest, the lightest

Have fun, get monstrous, and as always, keep exploring.