Picture of Building a unicorn costume
If you think the costume is magical or creepy...please vote for me in the Halloween Costume Contest:

I start every costume creation by finding an example that is done often, but not to an extreme level. I saw that the only unicorn costumes online were baggy store bought suits or a horn duct taped to someone’s forehead. I knew I could do better and add an X-Factor like fog snorting out the nose.

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Step 1: Foam foundation

Picture of Foam foundation
Create your foundational foam structure. I recommend using a combination of the dense core home foundation insulation and expanding foam (low expansion and high expansion). Cut the foam by scoring and breaking. Glue it together with Gorilla glue and definitely use clamps. You can insert pieces of wire at this stage to reenforce joints. Don't rush the gluing process and let it cure for a solid day or two.

You can then use your expanding foam to get a bulk structure for rounded areas.

Step 2: Foam Carving

Picture of Foam Carving
You want to start from coarse carving to fine finish work. The best way by far to cut foam is by using a hot wire tool. You can buy one online, but they are quite expensive. I recommend buying a $5 hair dryer at a thrift store, get the heating coil wire out, and then clamp onto the wire with a battery charger (car trickle charger worked great). You have to work in a well ventilated area without a doubt.

Once you have it roughed out, move to an electric carving knife which you can find at a thrift store also for about $10.

Then comes the dremel for the concave portions.

Finally I get the details done with a mesh drywall sander and dry wall spackle.

I also attached a photo showing a foam lego head I made last year to show the rough carving.
U no how would u no it burn u did u get burn by it
Partybot (author)  partypanda23451 year ago
None of the liquid came out which is what would irritate your skin.

at least you knew what was talking about I came back and I read my comment and im like what was I thinking it sounded like I was a little kid

Great job, I wanted to make a horse.... I guess this will work fine.
Mielameri10 months ago
Wow...what a large...horn you have there
Vtyler961 year ago
Hi.. How were you able to see out?
Partybot (author)  Vtyler961 year ago
I can see out the mouth and then the entire bottom of the lower jaw is wide open so it was super easy to see where I was going. The main annoyance was the weight. If I were to do it again, I would build a light metal armature using plumbing strapping, a bike helmet, metal wire that can be hot glued into shape, paper mache, and then upholster. It would cut weight by about 75%.

I'll be posting the techniques in a couple days when I add this year's Dragon costume.
poofrabbit2 years ago
Congratulations on being a finalist in the Halloween contest!!! Can’t wait to see if you win! Good luck!
Partybot (author)  poofrabbit2 years ago
Thanks! Hoping for the laser cutter tocreate something even better next year!
OOH that would be awesome!
poofrabbit2 years ago
This is fantastic!!!! Very well done 5 stars and a vote for you!
Tatterhood2 years ago
Yes. Yesyesyesyesyes.
jongscx2 years ago
I love unicorns...

but I'm gonna have to file this one under creepy.
OMG SO DOPE! I wish I was friends with you
rhino2 years ago
Unicorns are for gangstas.

A great instructable! You are very creative.
zomfibame2 years ago
Pretty cool costume.
dnoscar2 years ago
God Job LOL :P