My 12 year old son asked to be a Lava Lamp Costume for Halloween this year. To make the base, I took two oval laundry baskets and cut out the bottoms. I then stacked them and tied the bottoms together so that it made a figure 8 shape and he could stand in it, mimicking the look of the bottom of a lava lamp.
I covered both baskets with poster board, cutting the poster board so that it flared nicely. Then I wrapped the poster board in silver wrapping paper. I cut the bottom of a big red shirt to make suspenders and then tied two pieces onto the laundry basket so that the laundry basket part was being supported by the suspenders and his shoulders. I left it long enough so that the bottom of the costume was about ankle height. Because the laundry basket flared, it allowed him to be able to walk. He then wore what was left of the red shirt.
The next part was the hardest. I made a model of the clear part of the lava lamp out of poster board. I had to tape 4 large poster boards together to be able to cut the shape. The shape you are looking for is a trapezoid shape where the top is shorter than the bottom and the sides jut out at an angle. This will allow you to roll the flat shape into a cone with an open top that is thinner at the top and wider at the bottom. See below for the flattened version of the shape you will need:
Only once you have perfected the shape and your child can fit into it should you then wrap it in the plastic and then cut. You are looking for plastic that can hold its own shape. I found mine at the local hardware store, but could not find it at Lowe’s or Home Depot. It is used for porches as fake windows and comes on a big roll that you can cut to your desired length. The piece I bought was 36” wide and I bought a length of 6 feet which was long enough for my son. I then wrapped the plastic around the poster board model I had made and then hot glued the ends together. It worked perfectly and I had a clear plastic cone shape that I could then place into to the laundry basket base. It just sat on the rim of the laundry basket and I used lots of hot glue to glue the plastic to the base. I then rolled another open cone shape out of poster board and wrapped in in silver wrapping paper and that became the top. I left it open for air circulation, but I did tape in a battery powered press-on light that I wrapped in red cellophane for the lava lamp look.
The last thing I did was use “Great Stuff” which is foam filler that I bought at the Hardware Store and I made round and oval shapes to simulate the “lava” in the lava lamp. I spray painted them red and actually sewed them together with a big needle and left a long piece of string at the end. I then taped the string to the top piece and the lava hung in the middle of the clear part.
I have to lift and tilt the costume and my son raises his arms to get inside, but then the suspenders fit on his shoulders and the costumes hands just right. There is no arm movement, but he can lay his hands on the top part of the laundry basket. The costume is light and easy to walk in, but you have to be careful about falling since you can’t use your arms.