In the last few years, when considering what to make for a halloween costume, I've begun with characters which have had a strong, positive effect on popular culture.

Strong, popular characters which aren't really human.

I have a really good idea for Halloween 2009, simple in concept with just a couple of engineering challenges.

The first thing I did was to have Stacy take a photograph of me standing up. Lately I've started my design with a photo composite of myself behind an image of the character I'm transforming into.

Concept photo composites from previous years:

• California
• Jenga
• American Idol Judges
• Dwight Shrute Bobblehead
• Sees Candy

The primary challenge this year was where to hide my face. Generally, the first thing people look at is your face, so if you want them to look at your costume, particularly if your costume already has a face, you've usually got to obscure your own face.

This year's costume would need to sit high on my shoulders.

Lately I've abandoned the backpack frame in favor of just bending some PVC pipe with a heat gun. PVC pipes are about a dollar each, and I can usually avoid buying connectors by bending up the shapes I need.

I suggest bending PVC outside, because there is some fume and fire danger. You could probably use a hair dryer if you don't have a heat gun. You could probably use a space heater. I used to use a charcoal barbeque, so don't think you need the ideal equipment to pull this off.

Bending PVC is really easy. Don't let the length and complexity of these instructions concern you, I'm just trying to deliver as much information as possible.

Basically you just heat up a section of pipe until it gets soft, then you bend it.

To bend PVC pipe:

• Don't start with an entire 10 foot pipe unless you have to. A long pipe is unwieldy, especially once it has a couple of bends in it and starts knocking things off of shelves as you rotate it. Try to predict how long the finished project needs to be and cut the pipe first.
  
  
• Use a sharpie or other marker to mark where you would like the bend to start and end. Tight bends (smaller than 3" radius) are really tough, but these gentle ones are pretty easy.
  
  
• Prepare a wet paper towel or rag.
  
  
• Use the gun's highest setting to heat the area you would like to bend. Keep the gun moving, heating up a short area of the pipe (8 inches) for a tight bend or wider area (16 inches) for a gentle bend.
  
  
• Rotate the pipe in your hands so that the pipe gets hot all the way around. The heat doesn't travel far down the pipe, so I usually do this part with bare hands.
  

• After a minute of heating, try shaking the pipe to see if it is starting to sag. I usually heat it up a little more after it starts to sag. That seems to help make a nice clean bend without kinks.
  
  
• When the pipe looks weak enough to be bent to your will, turn off and set down the gun and pick up the wet paper towel.
  
  
• Bend the pipe, being wary of crimping the hose. You can use the wet paper towel to protect your hand and cool the pipe after it is bent. Often I will try to counter kinking by squeezing the sides of a collapsing pipe, forcing it back to a round cross-section. It is Ok if it isn't perfect, you know, unless it has to be perfect.
  
  
• I stole one tip from GK Bayne, she recommends bending pipe around a paint can or bucket for a smooth curve.
  

• Wipe the pipe with the wet paper towel to cool it down until it hardens, about a minute. There is usually some steam involved. The wet paper towel will transfer heat to your skin much quicker than a dry one, so be wary. It might help to have a bucket of cold water nearby in case your rag gets too warm. You could probably quench the whole pipe into cold water, but I don't know what that would do to the structural integrity of the plastic. Probably nothing.

A few people have suggested that I try filling the pvc with sand before I bend it, but I'm pretty comfortable with my method, so I haven't tried that yet.

Usually I try to make compound bends in separate steps, heating, bending and cooling, then re-heating, re-bending and cooling.

Never even once has my pvc pipe become too hot and melted into a globby puddle.

I was engineering this as I went. I needed a long rectangle sitting on my shoulders like a table.

The pipe for the shoulder harness required the most complicated shape.

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