Brain Cap HeaderA.jpg
By Jeromina Juan
If you’ve been brainstorming Halloween DIY costume ideas, no need to bang your head on a brick wall. It’s time to put on your thinking cap. Literally! With just a ball cap, squiggles of caulking (the stuff made for sealing tubs, sinks, and windows), and dabs of paint, this bloody brain is yours to wear on fright night.
It’s best to study pictures of the human brain before tackling this project in order to best mimic the brain’s convolution patterns when caulking the cap.
Weighing a little less than a pound and a half, this costume is still lighter than most professional bicycle and motorcycle helmets. Use a cap without an adjuster to ensure a perfect fit.
For a PDF of this tutorial, visit the build page on Make: Projects.


Fitted cap, without adjuster
Craft knife or seam ripper
Acrylic paint
, red and black
, approximately same size as cap
Tall jar
Plastic bag
2 tubes of latex or acrylic caulking (not silicone)
*, ivory or bone color
Caulking gun

*NOTE: Silicone caulking is not paintable.


Brain Cap Step 1.JPG
Step 1: Remove the cap’s brim by carefully ripping the seams with a craft knife or seam ripper.
Brain Cap Step 2.jpg
Step 2: Place the cap on newspaper. Paint the cap with dark red paint (a mixture of red paint and a little bit of black paint). Let dry.
Brain Cap Step 3.jpg
Step 3: On newspaper, create a work stand for your cap by placing a bowl upside down over a tall jar. Place a plastic bag over the bowl, and the cap over the plastic bag.
Brain Cap Step 4A.jpg
Step 4: With a craft knife, cut the tip of the caulking tube to have an opening approximately 1/2″ in diameter. Load the tube into a caulking gun.
Brain Cap Step 5.jpg
Step 5: Caulk convolutions on one half of the cap to create one hemisphere of the brain. Repeat on the second half of the cap.
Brain Cap Step 6.jpg
Step 6: Let the caulking dry for approximately one to two hours until the surface loses tack. Wearing gloves, lightly press on the convolutions to slightly flatten the surface.
Brain Cap Step 7.jpg
Step 7: Let the caulking cure for 24 hours.
Brain Cap Step 8A.jpg
Step 8: Once the caulking has cured, mix water with red paint and a little bit of black paint, to a thin, runny consistency. Use a brush to dab paint mixture onto the caulking, focusing on crevices. Apply a second coat if needed. Let dry.
Brain Cap Footer.JPG
Your bloody brain is ready to wear! You may wrap gauze to cover the seam between the brain and the forehead. Of course, the more fake blood, the better! Happy Halloween!
About the Author:
Jeromina Juan is the brains behind the blog Paper, Plate, and Plane, where she shares unique DIY ideas for all holidays throughout the year. She is partial to Halloween, being born on this special holiday.

45 thoughts on “Project: Gory Brain Cap

  1. You can color silicone with acrylic paint–it only takes a tiny amount. You could use the white stuff for the shape and use a small knife or spatula to spread on clear silicone colored with red so that it would be a glossy pink surface. This is a great idea. I thought about making one with coils of paper mache but this looks better.

  2. I used this idea for my daughter’s martian brain this year.
    The caulking was too heavy so I opted for ‘insulating foam sealant’ instead (buy at any home improvement store). It only took about an hour to dry completely (tack free in 15 min), was MUCH lighter and was easy to paint with acrylics too.
    I used the baseball crown as a form under a knit beanie so it would be the same shape as my daughter’s head (my first try without the ball cap form was too small and the beanies were only $2 so a trial run was cheap). The beanie was a good option because the ‘brain’ covered her entire head and was a perfect fit.
    Thank you so much for the idea! My daughter loved it!!

    1. I would like to do the project today for my son with foam as you sujested but does it show the same? Is it so smooth with the foam or it is kind of rough?

  3. I made this for Halloween this year, and it turned out great! I would suggest using a lighter option for the kids, but your suggestion worked just fine for me. A lot of the littler kids thought it looked real! :)

  4. In case you live and breathe for singing competitions, wonderful news (absolutely everyone else, really feel cost-free to sigh along with us): The CW is plotting one more 1.
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  5. It would also help to draw ‘map’ of brain squiggles you want to do on form before starting the big squeeze, so you get it accurately! Looks like fun! thanks!

  6. I do agree with all of the concepts you’ve offered in your post. They’re really convincing and can definitely work. Nonetheless, the posts are too short for newbies. May you please prolong them a little from next time? Thank you for the post.

  7. What about using those expanded polystyrene peanuts they use for packaging? Its basically what they use in crash helmets, so bonus!

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