A Cardboard Knight’s Helmet

I’m a recent convert to using cardboard for costumes.  This has been brought about by a child’s knight costume I saw online and from which this costume was entirely inspired.  Last year was a heavily duct tape costume, and I’ve even resorted to fabric in the past.

You can look at those armor pictures and get a good idea of how to put together your own kit.  Since the helmet was a real bear for me, I thought I’d walk through how I approached it.  Here’s the final costume, so you can see what the helmet looked like.

The first thing I didn’t factor in was the different varieties of cardboard involved.  In my case, I had a large TV box and some small Amazon boxes lying around and that was what I was going to use.  Some thoughts:

  • thinner is better.  The TV box was 2 layers of cardboard and too difficult to bend into the crown of the helmet.  It would have worked fine for the sides but would still have been challenging.
  • as you can see from this photo, you can even strip one layer of paper off the cardboard to get thinner, and a really interesting effect.  I used this to cover the seams in the knight’s helmet but felt it was probably too thin for the rest of the helmet.
Samurai armor made from a single ply of cardboard, with one layer of paper stripped off, to show the corrugated core
  • think about which direction needs to curve the most, and make sure you are cutting the cardboard so that the core within the two paper sides is perpendicular to where you want to bend it.  You’ll see what I mean – it’ll only bend one way really easily.

In the end, I needed:

  • about 2-3 hours
  • a couple of cardboard boxes that were more than a foot long and at least a couple of inches tall
  • scissors
  • a folding knife or some other sharp cutting tool with a handle: this is what I cut with the most because it’s faster and I could pull the knife along a ruler
  • a ruler and pencil
  • a hot glue gun
  • a patient child
  • a VERY patient adult

Getting Started

The first thing I did was to stare at the picture of the interior of the helmet!  It looked like the best way to start would be to create a frame that would ensure the helmet was big enough for the head.  Also, I thought it would make sense to have a piece going over the head to make sure it wouldn’t slip down.  Otherwise I wasn’t sure how I was going to make sure the eye slots were in the right place.

Create a 0.5″ strip to go around the knight’s head. Then cut a 0.5″ strip to go OVER the head. It will look like the top of a shopping basket when you’re finished.

The frame is pretty simple.  I made it a bit loose just in case Halloween was cold and the knight needed some extra padding.

The top piece is useful later as a place to which you can attach the outer parts of the helmet.

Note:  our knight wears glasses.  The glasses will stick out beyond the space of the frame.  When you are creating the outer edge layers – the sides – of the helmet, they should leave a gap between the front of the helmet and the inside of the frame.  Here’s what ours looked like in the end, inside the front:

A photo showing a gap left for a glasses-wearing knight

Build the Helm’s Sides

Once I had the frame, I started to add the sides.  These were just long strips that went all the way around the frame, leaving space for glasses.

The side layers are glued to the frame and each other.

The first layer (layer 1) was 4 inches at the front and tapered to 2 inches at the back.  The second layer (layer 2) went on top of that, and was a uniform 2 inches all the way along.

By putting a narrower layer on top of a larger layer, you get something that looks a bit like visor

I cut the eye slots in the first layer before I glued it, but I didn’t cut the second layer until it was glued onto the first layer.  You’ll see in the photo of the final helmet that there is a small piece of cardboard that looks like a beard.  That’s glued to the inside of layer 1.

The Crown

This was a bear.  In part, because I knew the cardboard was going to be hard to bend into the form.  I have done a similar helmet in the past, using foam sheets and so had an idea of the challenges.  I decided to start by gluing a wider strip across the frame top.

The three pieces of the crown. There are no measurements because I didn’t use any.

The center piece was wider – say, an inch – so that I would have the ability to glue tabs to each piece to hold them together.

The sides of the crown are moon-shaped pieces of cardboard. The straight edge should be the same length as the piece you placed on top of the crown.

There is probably a mathematical formula for how big the side pieces of the crown should be.  I did a rough measurement from the top center of the top piece down to the edge of the side, to estimate how wide this should be.


Small tabs hold the helmet crown to the sides, and to other pieces of the crown

Probably the toughest part of this is finding ways to connect each element.  In the end, I used a lot of tabs – small rectangular pieces of cardboard, often 2 inches long and about half an inch wide – to glue to the side of the helmet first, and then to glue to the crown.

In the end – and you can see it from the final photo at the bottom of the post – one side is slightly higher than the other.  I glued the straight edges to the center piece first, and then attached the curved pieces to the sides.  Where they didn’t align very well, I trimmed them as I went.

The sides of the helmet’s top (crown) attached to the center piece, but not yet attached to the sides

Note:  this will leave gaps and could be quite messy.  As you can see from the inspirational helmet, which looks very polished, my approach will not result in something so polished looking.  I had some triangular gaps remaining that needed to be filled.  It looks very ugly when it’s just cardboard, but I used some tricks to cover them up so that, in the end, they were invisible from the outside.

To patch, cut an approximate piece of cardboard, put a bit of hot glue on the edges or back, and put it into place like a jigsaw piece.

Mask the Imperfect

I knew I was going to paint the helmet, which would cover up a lot of the imperfections.  However, as I’ve learned on previous costumes, you can make them completely disappear before the paint.  In my case:

  • I added a crown attachment to the helmet (like a tiara), which would hide the seams of the helmet top attaching to the helmet sides
  • I stripped down two 1 inch-wide pieces of cardboard, and ran them across the top seams of the helmet, making a textured effect
  • I added a large ovoid shape at the back to hide the seams and add some decoration
You can add decorations or ornaments to cover up the seams of the helmet and, once it’s painted, most of the defects should be hidden

The end result was pretty satisfying and I was glad to have something other than the typical bucket helmet.  The young knight was quite pleased with the helmet.  He pulled a neck gaiter up over his neck and ears for warmth and coverage against foes and it still fit comfortably.

Heavy are the eyelids of the person making the crown … but totally worth it.
David Whelan

I improve information access and lead information teams. My books on finding information and managing it and practicing law using cloud computing reflect my interest in information management, technology, law practice, and legal research. I've been a library director in Canada and the US, as well as directing the American Bar Association's Legal Technology Resource Center. I speak and write frequently on information, technology, law library, and law practice issues.