Plastic bowls to use as forms — I bought this set of plastic stacking bowls, but you can get creative with molds!
Cooking oil — I used canola oil, but almost any oil will do the trick.
White concrete mix — I used leftover concrete countertop mix from our kitchen countertops, but you can usually find white concrete at your local hardware store.
Drill with mixing attachment — this is not 100% necessary for this small of a project, but will make the mixing an easier job.
Bucket — for mixing concrete in
Hammer — for tapping the sides of your molds to help settle air bubbles
Rocks — or any other weighted object to hold the smaller mold in place
Sand paper — I found that 120 grit was good to sand any bigger areas quickly and finished with 400 grit for a very smooth finish.
1. Hammer nails into the tops of the bowls.
1. Hammer nails into the tops of the bowls. These will help the forms stay equidistant apart from each other so you won’t have too thick or too thin of a bottom. The nails should be as close to the top as possible. You can see in our process photo below that we were working ahead and gathering our rocks for step 4.
2. Grease the forms.
Nonstick cooking spray or canola oil works for this. Make sure to coat any part of the form that will be in contact with the concrete. Typically this will be the outside of the smaller mold and the inside of the larger mold.
3. Add some concrete mix into a bucket and mix with the drill and mixer attachment until it is about as thick as pancake batter.
Pour the mixture into the larger bowl. Pour it about 3/4 full If you want the form to be all the way full, or less if you want a bowl with lower sides.
4. Tap the larger bowl with a hammer to help settle the air bubbles.
Do this for about a minute and then press your smaller bowl inside the larger bowl that is filled with concrete. Hammer it some more to minimize air bubbles. Fill the bowls with rocks to keep the top form in place.
5. Wait 24 hours before taking them out of the forms.
They should pop out without too much effort.
6. The bowls can be done as soon as you take them out of the mold, or you can choose to sand the bowls for a smoother finish.
We used 120 grit for the very bumpy areas and worked our way down to 400. It’s a good idea to wear a mask during this step because concrete dust is a known carcinogen.
And that’s it! A simple project with a beautiful result.