It’s been too long since my last post on this subject. I have 3 or 4 lined up but have not had the time to dig into them. I thought I would get back into it with a post on how to make concrete planters.
Quite a few friends and readers have e-mailed me and asked for more information on how I made the pot shown at the end of the second article in this series, A Thinner Mix. I have made a lot of progress since then. Here is an example of some new planters/pots I have made.
Large, medium and small concrete planters. The large one (back left) came out of a bigger mold, but I did not pour the sides as high.
Making The Molds
To make the molds, I used a variety of containers, and drilled a hole in the center of them.
TIP: Be as accurate as possible finding center as this will ensure that the concrete planters have an even wall thickness.
This first one, my medium-sized mold, uses a Paderno melamine mixing bowl for the outside, and an old plastic light dome for the inside. The dome gives a beautiful rounded interior to the finished product (see images at the end of this post). I found it in a second-hand store. I have been looking for more in different sizes but they are really hard to find and new ones are REALLY expensive!
Paderno melamine mixing bowl and an old plastic light dome.
This smaller concrete pot mold is made from 2 Paderno mixing bowls.
2 Padero mixing bowls
Note the bottom of the smaller red one, above. The bottoms of these bowls have a ridge as you can see in the blue one below. These ridges leave an unfinished look to the inside of the bowl. I used an orbital sander with 60 grit to remove the ridge from the red one. Then I worked up to a 220 grit to get it nice and smooth. I then gave it 3 coats of carnauba wax.
Another way to do this is with Bondo automotive body filler. This next image shows a plastic pot which is perfect for the inside half of my extra large mold. I used Bondo on it, then sanded with 220 to get it super smooth. Then I gave it 3 coats of carnauba wax.
TIP: Note that I am using melamine and plastic pots for the molds. Stainless steel also works – BUT these molds do not release nearly as well and will dent easily.
The Spacer
The spacer is a very important part of your mold. It will form the drainage hole for the concrete planter and also hold the 2 halves of the mold together, like this.
The parts below are a 5/16 bolt, 2 washers, a copper plumbing fitting (3/4″ OD) and 2 smaller pieces of plastic tubing cut to the same height as the copper fitting. In the second picture, you can see that the tubing has been placed inside the copper fitting. This gives me a nice snug fit for the bolt and also, when it is tightened up, the plastic tubing helps make a seal that the concrete can not leak through. I use a copper fitting only because it makes for a nice detail in the concrete planter as you will see in the images at the end of this post.
Here is the outside part of the mold with the bolt through it and the spacer in place.
TIP: If you do not want the copper detail, you can make a simpler spacer out of a rubber stopper which you can easily find at brew-it-yourself wine/beer supply shops or at any place that sells stoppers for test tubes.
Here is the assembled unit. Note the nice symmetry – even spacing between the mold halves.
The steps on how to make a concrete planter mold
Once you have all of your parts made, all you need to do is:
- Wax the outside of the inside part of the mold.
- Wax the inside of the outside part of the mold.
- Spray some release agent on the outside of the inside part of the mold.
- Spray some release agent on the inside of the outside part of the mold.
- Assemble the mold as shown above. Take your time here, being sure to get as even a spacing as possible between the 2 mold halves.
- Pour your concrete as shown in the graphic above. You will need a thin mix for this!
- Allow to set for up to 24 hours (unless you are using the Kast Krete mix I discussed in A Thinner Mix.)
- Unbolt the mold.
- Gently pry on the inside part of the mold. It should slide out pretty easily.
- Now flip the outside half of the mold upside down and lay it flat on a towel, or a piece of Styrofoam. Using a rubber hammer, gently tap on the top and sides until the concrete planter releases and drops out. If it is not coming out, turn it over and gently apply outward pressure on the side of the mold. Work your way around the mold. You will see a very small gap start to develop between the mold and the concrete. Now turn it upside down and again tap on the top and sides. Just be patient. It will pop out – unless you forgot your release agent!
- Optional: I always sand the top edge of the planters. Some folks like to leave them rough. Experiment and see what works best for you. I talk a bit about sanding in this post.
Notes:
For steps 1 and 2, I use a spray-on car wax. It just makes the mold more slippery and easier to release the concrete (especially if you forgot to apply the release agent, which I have done several times … DOH!). Every 4 or 5 times I use the molds, I give them a coat of carnauba wax to seal them up and cover over tiny scratches that come from cleaning them after each use. I use Trewax clear paste wax for this.
For steps 3 and 4, I use Smooth-ON Universal Mold Release. It’s a great product and easy to use. I have also used mineral oil which works very well. Pam also works but I find it leaves a food odor on the finished product. It does wear off over time though.
For step 6, I typically use Starpatch Concrete Products Kast Krete because it can be mixed to a pancake batter-like consistency. Very easy to pour. But I have also used Starpatch’s Countertop Mix and Quikrete’s Countertop Mix. Both are harder to pour in that small space. BUT – Starpatch sells something called a flow kit. When I add this to their Countertop mix, the mix becomes MUCH more fluid and easy to pour. ALSO – there is a new product out there called ShapeCrete. It’s available in the USA from Home Depot but not here in Canada yet. Looks great! Do a YouTube search for shapecrete and you will find many cool videos. I am really looking forward to trying it when it becomes available up here.
TIP: A great thing about these molds is how flexible they are. If you want lower sides (a shallower concrete container) pour in less concrete. If you want higher sides, pour in more. Have fun experimenting.
The Results
Here is a concrete planter made with Kast Krete. You can see the copper detail in the drain hole.
Here are 6 more images for you to look at of concrete planters and bowls using the molds described in this post. The rougher ones were made with Countertop mix. Click any image to see the large version.
I hope that you have found this information of use and that it will be helpful to you making your own concrete creations. If you have ideas you would like to share, please leave a comment. I’d love to hear about what you are doing with concrete!
Read more in this series:
Part 7 – Concrete Creations: Water Feature Ideas
Part 9 – Concrete Creations: Rubber Molds! – coming soon!
Photo Credits
All photos by Gil Namur – All Rights Reserved
Hi gil,
I have tried using Kast krete however my products come out quite chalky.
I also added some acrylic paint to colour my white concrete and the outcome is pretty disastrous.
Do you have any suggestions on how i can get close to white concrete since i cant find any ? I live in vancouver too but I’m not very experienced with concrete.
I also bought white cement but having major issues with hairline cracks and since I cant find white sand, I am running out of options.
Thank you!
Hi Cleo (Jamie),
Not sure what to suggest. I had very good luck with Kast Krete. Have you tried calling them? There is a fellow there by the name of Bendix Jessen who is very helpful.
Actually, I will ping him and see if he can weigh in on this thread.
Cheers,
Gil
Hi Cleo,
I have two thoughts. Cement All is a rapid setting cement and is fantastic. It’s available in your area. It will be off white, but if you add a white zinc oxide powder, it will be white. You can also add white acrylic paint, but not all acrylic paints are the same and some can ruin your project. Do you have Michael’s craft stores up there? If not, I think you can get this paint from Amazon too. It’s called CraftSmart. It’s cheap, and works.
If you do have a Michaels up there, they carry a wonderful cement from Artminds -White Outdoor Cement. It’s supposed to be for mosaics, but it’s perfect for concrete crafts. It has a nice texture and is very white. I have lots of details about pigmenting cement on my site- https://artsyprettyplants.com/concrete-crafts-pigments/
Hi Ellen,
Thanks for weighing in on this 🙂
Hope all is well in your world!
Cheers,
Gil
Hi Gil,
Everything is great! I’m finishing up an ebook on concrete crafts and am linking this post to my resource page within the book. Your concrete creations series has helped me get where I am today!
Hi Ellen,
That’s GREAT! Good for you! Please let us know when it’s done and you would be most welcome to have a guest post here!
I am going to try Cement All and Artminds -White Outdoor Cement.
I kind of switched gears a while back and started building & fixing furniture.
If you are on Facebook – have a peek at this page – and please like it if you like it 😉
https://www.facebook.com/VintageStation.ca/
I build and fix – and my wife does all the finishing 🙂
Stay safe!
Cheers,
Gil
Hi Gil,
I have learned a lot from all of the above posts, thank you for this. I have been making concrete bowls, plates and big candle holders but using either a white fine mortar or a cement & fine sand mix since I can not find any Kast Crete or quickcrete here in France.
Have you experienced any mixing of cement and fine sand that gives the same results as Kraft crete?
For your thin wall items, do you add the glass fiber to your kraft crete? And looking at the video you posted on the other company it looks like he is adding a latex or resin additive (milky liquid), do you add anything like this to your Kast crete? Also, in the other video, the guy doesnt tap the moulds much to get air bubbles out, do you do this?
Thanks so much in advance and I really appreciate any help or information you could give me.
Hi Marieke,
Thanks for your comment! I do not have any experience mixing cement with fine sand nor have I added any latex or resin. The Kast Krete is a polymer modified mix that has fiber in it already.
Have you tried counter top mix? Most concrete companies make a mix for counter tops that can be poured pretty thin and has fiber in the mix. I have used some and the results were very nice.
As for tapping, what I do is tap the bucket of mix a lot first with a rubber mallet. Then, after the pour, I gently tap the mold for a minute or so.
I hope this helps!
Good luck with your projects 🙂
Cheers,
Gil
Hi Gil,
This series of concrete posts have been the most useful and informative I have found. Really, so helpful. I have a website with misc diy tutorials and this will help me so much with all my concrete project ideas. I made some round ones and had mild cracking. I noticed the post is from 2016. I don’t see your post on the rubber molds. Did you end up doing them? I’d love to read about that. Also, I see you don’t have a way to pin from your site to Pinterest. You should do that. You’d get a lot of traction. Wish I had found you sooner.
Hi Ellen,
Thanks for your kind comment! Did you post on the round ones you made? If so, leave a link for us to see!
There are Pinterest sharing options at the end of every post. Do they work for you?
I did build a few rubber molds and they work great. I never posted on them because we moved in 2016 and it was a busy time on all fronts. I did take pics and will post that in the next while.
Thanks again for taking the time to comment!
Cheers,
Gil
Hi Gil,
I look forward to reading your rubber molds post. I did miss the Pinterest icon. I was looking at the top. I have it now, thanks. Yes, my planters are posted. They are pretty small, but turned out nicely. I used very white, smooth concrete called Buddy Rhodes Artisan. I don’t have anything to compare it to, but it was very fine and smooth. These are 2 small planters. I plan on making lots of different things with concrete. Here’s how they look- http://artsyprettyplants.com/make-things/planters/
Hi Ellen,
Thanks for sharing! Very nice. I also really like your Driftwood Planter!
Cheers,
Gil
My bonsai can not in any way have lime in a concrete mix. All mine need a acidic soil. Do you have any ideas or insight into what mix I could use for making my own bonsai containers? Thx
Hi! What did you use in putting holes of your melamine wares? Thanks!
Hi Mhai,
I do not understand the question. Do you mean how did I make holes in the bowls I used? If so, I used a drill.
Cheers,
Gil
I am also from Australia and have experimented with mixes. I would love to source the Kast Krete out here, do you have any contacts of something similar please?
very very inpiring site thank you Gil! I have been ‘playing’ with concrete for the last 6 months or so and have been looking for ideas and inspiration. I am attempting to get a smooth finish on concrete cylindrical shapes – I have been using stiff cardboard with a shiny finish to form the cylinder but it’s not the ideal material to use as it becomes flimsy very quickly once the concrete mix is poured in. I am in Australia and, like Kim, love the sound of the Kast Krete you use….any help appreciated!
Thanks Sarah!
There is a type of plastic sheet that is about the thickness of poster board ( like kids use for school projects). It’s called Styrene and it comes in a variety of sizes and thicknesses and is easy to cut. It would stay stiff and also be reusable. Out my way, there is a store called industrial plastics that sells it.
Here is a link to it. I am sure that there would be someone out your way that could provide you with something like this:
http://goindustrial.ca/index.php/en/products/94/46/signs-display/sheets-substraits/styrene-sheet-detail
Good luck!
Cheers,
Gil
Hi Kym,
Sorry for my slow reply to you. I do not have any contacts out that way.
Best idea would be to speak with local concrete suppliers and show them the Kast Krete product and ask if they have something similar. Show them this link (or print it off and bring to them).
http://www.starpatchconcrete.com/product-42-Kast-Krete
Hope this helps!
Cheers,
Gil
Inspirational! Thank you
Hi thank you for your instructions very good!!, I live just outside London UK I’m trying to find Kast Crete do you know if this is available outside the US or something similar.
Many thanks
Very useful artikel. Thank you. I try to creat such planter mold involving something from my style 🙂
Hi – I have attempted some concrete planters but found as soon as I put the plant in the pot within a few days a small thing crack starts to appear in the concrete. I am in Australia and currently just using white cement and white sand mix but I think I will try and locate the equivalent of the cement products you are using. Do you find them cracking at all once the soil and plants go in??
Hi Amanda,
Indeed! I have had a few that did that and have yet to figure out why. But, only square (rectangular) pots. Not round ones.
When I figure that out, I will post about it.
Cheers,
Gil
Thank you for your response. Hmm mine are round – I guess it is just luck of the draw hehe – I will keep my eyes peeled for anything you may write regarding it in the future! 🙂
Hi Amanda,Just wondering if you have managed to find a similar product to KastKrete here in Australia?
I am currently trying to master this skill.
Thanks Kym
I have been following each of these post as I slowly delve into concrete planter making (I need to plan less and more trial and error lol), I can’t wait to read part 9 as I’m currently in the design process of building silicone holds for my next project.
Hi Laura,
Thanks for taking the time to leave a comment!
And thanks for reading. I hope they have been helpful to you!
Cheers,
Gil
Very well thought out and executed set of instructions for making concrete and concrete related articles. Your work is appreciated. Thank you.
Thanks Rosemary!
I am glad they are of use. It’s a fun little hobby for me and still so much to learn! More posts coming soon 😉
Cheers,
Gil
Gil – thank you for the info on how to put in a drainage hole! You make it seem so simple – I will definitely be trying your method in the near future!
Hi Christie,
You are most welcome! Thank YOU for taking the time to leave a comment 🙂
Cheers,
Gil