Introduction: Mini Concrete Planters Using Plastic Bottles
This week I made some small concrete planters, using old plastic containers as molds.
This was first time working with concrete, but I do have some mold making and casting experience from school, albeit rusty. If you're a newbie like me, these two free Instructables Classes will be extremely handy:
For this project, you will need:
- Concrete mix (or cement mix, mortar mix, since we'll be sifting out the gravel)
- Small gravel (or reuse from concrete mix)
- Plastic mixing containers & stir sticks
- Plastic containers with an appealing shape, of various sizes
- Plastic drinking straw
- Hot glue
- Heavy duty scissors
- Utility knife
- Pliers, awl, etc. for demolding
- Gloves (optional but recommended)
- Dust mask
- Small succulents or other plants
- Potting soil with good drainage
- Succulent gardening tools (optional)
- Decorative sand (optional)
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Step 1: Make Molds
First, I cut down some plastic Suja juice bottles, which I thought had an interesting shape. Since I want water to be able to easily drain out of the planters, I glued a piece of a drinking straw to the bottom of the bottle.
For my inner shell, I used an old film container, but you could also use an empty cosmetics bottle, or whatever you have around. I glued the inner shell to the straw, and some chopsticks to both shells to keep the inner shell centered.
I made one at a larger scale, with the juice bottle as the inner shell. I can't remember where the harder plastic container came from, but it was time to clean the studio and get rid of unnecessary stuff. Plucking things from a junk drawer to make them useful one last time before recycling is one of my favorite ways to declutter (albeit slow).
I had a can of mold release kicking around so I gave them all a quick spray. This step is optional and I'm not sure it helped in the end, but typically you can substitute a vegetable oil cooking spray for mold release if you really want to experiment (though the oil may stain the concrete).
Step 2: Sift, Mix, & Pour
I sifted out the aggregate gravel from the concrete to create a smoother surface on the finished product.
I know, now it's just cement! Mortar mix! Why isn't this project called "Cement Planters"?! Oh the outrage, the horror. Well, the concrete mix was cheap, you can find it at any home center. And we'll reuse the gravel for planting the succulents later. Plus now I have more regular concrete leftover to make something else (potentially larger) in the future. TBH it's also for SEO.
Then I mixed in some water until I got a thick mixture, but that was still pourable. I added too much water at first, and had to add more sifted concrete to get the right consistency.
I tried to fill up the molds to about the same height, and set them on a level surface to cure. If you have one available to you, I recommend using a vibrating palm sander without any sandpaper to vibrate the full molds. This helps get the bubbles out of the concrete.
Step 3: Cure & Demold
About 24 hours later, I set about removing them from the molds. This part can be a little dangerous, so just remember that the plastic can give way at any moment, driving your tool in whatever direction you're pressing it, so keep your body parts out of the way.
I had an ok time with the plastic bottles, but had to resort to some power tools to open up the stiffer plastic. While the planters are still a bit wet, it's easier to shave down any sharp edges.
Step 4: Oops! Repair
I broke this one by squeezing the film container, so I let the pieces dry and used a bit of construction adhesive to glue them back together.
Step 5: Fill 'Em With Plants
All that remained was to fill up the concrete planters with succulents. I put a little gravel at bottom, then pack the plant in with some succulent soil which has good drainage. I topped off the planters with a little more gravel and some pretty sand.
Step 6: Style & Enjoy!
I had a great time dipping a toe into a new medium, and look forward to making more concrete projects in the future. How would you style these planters in your home? Do you have any advice to help this beginner improve her technique? Let me know, and show me yours in the comments below.
Fore more knowledge and inspiration, try these free Instructables Classes:
Thanks for checking out my project. I'm always working on something new, so follow me here on Instructables! If you liked this one, you might like:
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5 years ago
I was thinking about trying this but instead of cutting off a plastic bottle I was considering using a heat gun to loosen it up or even put it in the oven (after it is fully dry) to help melt/stretch the plastic mold away.
Just a thought. Thanks for posting.
5 years ago
I've been wanting to do stuff with concrete for quite a while, thanks for putting this back up towards the top of my list. One thing I've seen to make them look more unique was to dip them partly in paint, so one half is still concrete coloured. Also some adhesive plastic feet are nice to not damage the surface you put them on.
One question: you put a hole for drainage in them, do you have anything you put underneath them for catching that water?
Reply 5 years ago
Yes, you can see the larger one has a concrete coaster to catch water, but generally I take the plants to the sink and let them drain before putting them back in the window. Paint is on my list to try!
5 years ago
I've done some concrete stepping stones and I used vaseline as a mold release. Worked pretty well.
5 years ago
Love this project! Very simple, very useful! I'll sure make some myself. I might even try using a plaster mix. Thx guys for sharing it with us!
5 years ago
Just a thought, but some colored epoxy for that cracked one could have been fun.