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!

Comments

author
hbridge88 made it!(author)2015-11-10

Such a creative idea. Love it!

author
pheenix42 made it!(author)2015-10-23

Sounds hard to me... ;)

author
Butane+Flame made it!(author)2015-10-17

love it, can't wait to do this; this weekend!

author
NathanSellers made it!(author)2015-10-16

This is an awesome idea. What did you use for your light?

author
ShapeCrete+Mix made it!(author)2015-10-16

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.

author
Scott594 made it!(author)2015-10-16

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!

author
ShapeCrete+Mix made it!(author)2015-10-16

That's a good idea about the balloon, it would also make the inside a bit smoother.

author
Just4Fun+Media made it!(author)2015-10-16

Very interesting project! It would definitely save a lot of pumpkins. How heavy is the final product?

Have a great day! :-)

author
ShapeCrete+Mix made it!(author)2015-10-16

Thanks, have a nice weekend!

It weighs just under 10 lbs. Thickness varies from 1/2" to 3/4"

author
Jedi_zombie85 made it!(author)2015-10-16

really nice idea mate,

author
gravityisweak made it!(author)2015-10-16

I'm waiting patiently for some Shapecrete to show up in some stores around Boston!

author
kpantel made it!(author)2015-10-15

would placing chicken wire or some other form of metal support inside the concrete as you mould it make it stronger ?

author
ShapeCrete+Mix made it!(author)2015-10-15

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.

About This Instructable

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Bio: ShapeCrete is a just-add-water-and-use, shape-able concrete that can be poured, rolled, pushed or molded in an infinite array of custom concrete designs. ShapeCrete is rolling ... More »
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