A concrete form tube is almost all you need to make this side stool. The finished piece is hollow and weighs about 20-25 lbs. depending on the thickness.

Materials and Supplies:

Rubber Gloves, Safety Glasses, Dust Mask
10" Concrete Form Tube
Shelf Liner
Spray Adhesive
11"x11" Plastic Sheet
Base Surface
Duct Tape
Mixing Containers
25 lbs. ShapeCrete

Tools:

Hand Saw
Utility Knife
Ruler / Square
Hot Glue Gun
100% Silicone Caulk and Caulking Gun
CHENG Corner and Seam Shaping Tool
Razor Blade
Trowel
Diamond Hand Sanding Pad

Step 1: Cut Down Concrete Form Tube

Measure down the form tube and make marks with a pen at 18".

Tape around the tube to connect the marks. The tape will act as a guide, making it easier to cut the tube straight.

Cut the tube to size with a hand saw, utility knife, or band saw.

Step 2: Glue Shelf Liner in Place

This is the trickiest part of the project, but it's optional. Gluing a plastic shelf liner inside the tube will give the finished piece a texture. The shelf liner here is just over 18" in width, so it fits perfectly inside the 18" tall form tube.

Tape the shelf liner in place, working your way around the inside of the tube and making sure that the liner is tight against the inside.

Make a mark on the liner where it meets the starting point.

Cut the liner to length with a utility knife, using a ruler as a guide.

Lay down some contact paper and spray the non-textured side of the shelf liner with spray adhesive. Follow the directions on the adhesive and spray the interior of the tube, then wait 5-10 minutes for the adhesive to get tacky.

Carefully place the liner inside the tube and press it into place.

Trim away excess with a utility knife.

Step 3: Make the Base and Glue Down the Tube

Make the base for the form tube using something flat, like a scrap piece of plywood, or in this case, a terracotta tile that was laying around. Tape a piece of plastic (11"x11") to the tile. The plastic will make it easy to remove from the piece later.

Tape the plastic down on the tile.
Place the form tube in the center of the tile.
Run a bead of hot glue around the base of the form tube to hold it in place.

Step 4: Silicone the Inside Edge

This step is also optional, but it will create a nice round-over on the top edge. If you skip this step, the top will have some sharp edges that need to be sanded down with diamond hand pads.

Run a bead of caulk around the bottom inside edge of the tube.

Tool the caulk with a seam shaping tool (an acrylic rod cut at an angle).

Scrape up the excess silicone with a razor blade.

Wait for the silicone to cure and then pull up the excess silicone from the sides of the tube.

After the silicone has fully cured, clean out the form with denatured alcohol.

Now the form is ready to pack.

Step 5: Mix ShapeCrete

A project this size will take about 25 lbs. of mix, at about 5/8" - 3/4" thick. It helps to mix this amount in a 5-gallon bucket or a concrete mixing tub.

Mix ShapeCrete to a Clay-Like Consistency.

Add half the water to the tub.

Add the dry mix with the dry pigment already blended in (optional).

Blend thoroughly by hand or with a paddle mixer. The mix should hang vertically when it's the right consistency. Adjust water content as needed.

Always wear a rubber gloves, safety glasses, and a dust mask when mixing.

Step 6: Pack the Form

Begin by packing the bottom of the form to an even thickness. Press the mix into the edges of the form so you don't leave air bubbles.
Gradually pack the mix up the walls of the form, turning it as you go along.
If the mix is slumping down, it may be too wet. Try pressing thinner pads into the form and then coming back with a second layer to thicken it up.
When you get to the top of the form, smooth the top edge with a trowel or putty knife.

Cover with plastic and let it cure for 24-48 hours before removing it from the form.

Step 7: Demold

Stripping the form is easy.

Remove the tape from the tile so the plastic is loose.
Flip the piece over and peel away the plastic.
Use a utility knife to carefully slice into the tube and gradually peel it away. Be careful not to cut too deep into the piece.
Sand any jagged edges with diamond hand pads, files, or coarse sandpaper.

Step 8: The Finished Piece

Concrete form tubes are really versatile and come in a huge range of sizes so they can be used to make a lot of different (cylindrical) things. The tubes can be packed to form planters, waste bin surrounds, small containers, or short side tables like this project.

Thanks for reading and following!