Introduction: Concrete Jack-O'-Lantern
Neighborhood vandals always kicking your jack-o'-lanterns? This year, why not surprise them with something more concrete?
This is a really quick project and much less messy than carving a real pumpkin, except you don't get to bake and eat the seeds or throw the slimy stuff on your friends and family.
All you need is a plastic pumpkin from the dollar store, a box knife, and about half a bucket of ShapeCrete.
Materials and Supplies:
- Pumpkin Shaped Candy Pail (Walgreens / CVS / Dollar Store, etc.)
- 10 lbs. ShapeCrete
- Rubber Gloves, Dust Mask, Mixing Supplies
- Plastic Sheet
- Permanent Marker
- LED Light, Candle
Tools:
- Scissors
- Utility Knife
- Spoon
- Misc. Carving Tools
Step 1: Draw and Cut Your Design
Draw out the design on the pumpkin with a marker. If you don't like what you've drawn, start over by erasing it with rubbing alcohol.
Carefully use a utility knife to cut out the shapes.
Step 2: Pack It With ShapeCrete
Mix ShapeCrete to a clay-like consistency.
Pack the mix in the form, starting from the bottom and working upwards. This piece is about 5/8"-3/4" thick.
Larger holes can be left open, but in this case the mouth had to be packed and then carved away. If we didn't do this, the walls would probably slump down. They need a little bit of support at first, but as the mix stiffens up, it'll stay in place.
Pack up to the top opening. It helps to roll the mix over the edge a bit to get it to hang in place when the shape curves in on itself like this.
Step 3: Carve Out the Mouth
The utility knife is really useful here. You slice the mix, gradually digging it out, and then smoothing the cut with the side of the blade. This will give it a nice flat surface.
The smaller tools are useful for the more detailed spots. The handle of the spoon was good to smooth out the tight places.
The weight of the piece was pulling the mouth down, so I put a plastic wedge in there to help hold it up. In hindsight, this wasn't a great idea because it was a pain to remove and had to be drilled out. If this happens to your piece, use a piece of cardboard or something less rigid instead.
You have at least 30 minutes of work time and more depending on the environment. In a cool, shady spot, you'll have more time than out in the hot sun.
Step 4: Shape the Top
On a clear piece of plastic, draw out the approximate diameter that the top should be.
Shape the top by hand and use different tools to add detail.
The nice thing about the clear plastic is that you can put it on top of the pumpkin and see how it lines up.
When you're finished carving, cover the pieces with plastic and let them cure for 24-48 hours depending on the level of detail in your piece. This one came out of the form the next day.
Step 5: Remove the Form
The plastic mold has to be cut away. Do this carefully so you don't slice into the piece or yourself.
Use diamond hand pads or sandpaper and files to finish the edges. I used a flat screwdriver and banged on parts of it with a hammer to clear out the mouth a bit more.
Step 6: The Finished Piece
Put a tea light or LED light in the pumpkin and that's it.
The piece can be stained or painted if you want a more convincing pumpkin and you really do hope to break some toes this year.
Have a happy halloween!

Runner Up in the
Halloween Decor Contest 2015

Runner Up in the
Pumpkin Challenge
16 Comments
1 year ago
Is there an alternative to Shapecrete?
Home depot says it's discontinued and Amazon is no longer is carrying it either.
1 year ago on Step 6
What a fabulous idea! Just turn him around for Thanksgiving, fill him with leaf branches and you're set to go. Love it.
5 years ago
Awesome. It doesn't rot ether, so that problem is solved.
7 years ago
Such a creative idea. Love it!
7 years ago
Sounds hard to me... ;)
7 years ago
love it, can't wait to do this; this weekend!
7 years ago
This is an awesome idea. What did you use for your light?
Reply 7 years ago
I used the rear LED light from my bike to snap some quick photos, but around Halloween I want to see it with candle light and an orange glow.
7 years ago
It may be helpful to inflate a balloon inside to hold the shapecrete in place over large features. it will also help slow the cure which adds strength.
Very cool!
Reply 7 years ago
That's a good idea about the balloon, it would also make the inside a bit smoother.
7 years ago
Very interesting project! It would definitely save a lot of pumpkins. How heavy is the final product?
Have a great day! :-)
Reply 7 years ago
Thanks, have a nice weekend!
It weighs just under 10 lbs. Thickness varies from 1/2" to 3/4"
7 years ago
really nice idea mate,
7 years ago
I'm waiting patiently for some Shapecrete to show up in some stores around Boston!
7 years ago
would placing chicken wire or some other form of metal support inside the concrete as you mould it make it stronger ?
Reply 7 years ago
It wouldn't necessarily make this piece any stronger, but if it were reinforced with chicken wire or fiberglass mesh, that would keep it from falling apart in case it ever broke (if someone hit it with a baseball bat for example).
A mesh will help when you're laying up the mix on vertical surfaces, but on a project like this it's probably more trouble than it's worth. It's already really solid at 3/4" thick.