Introduction: Pots From Sand and Cement, NO MOLDS
This instructable will show you how to make flower pots and planters using just sand and cement without any molds.
A small putty knife or small trowel
A turntable that I will show you how to make
Scrapers to form the pot, more about this later.
Step 1: Making the Turntable
I made a turntable out of a 6 inch Lazy Susan bearing that can be bought for around $6.00 at your local big box hardware store. The rest of it was made from scrap material I had on hand. I made this one to make small pots up to 7.5 in diameter. There are many ways to make a turntable this is just an easy one I think most people could make.
I used a piece of 2x4 with two scraps of plywood screwed to the bottom for supports and a square of plywood screwed to the top just large enough to hold the bearing. Screwed the bearing down on this. Then screw a circle of plywood to the top of the bearing. A piece of 1x4 screwed on to the 2x4 vertically and another piece screwed to the other side of the vertical, horizontally. This makes the other side of the horizontal piece over the center of the 2x4 and also the turntable. I had a bunch of 8 inch tiles so I centered one on the turntable and made two corner brackets out of 1/4 inch plywood and screwed them in place. So I could put a tile down and it will be centered and held in place.You do not need to use tile, you could use a piece of plywood or any thing else that is stiff enough to not bend when you lift it with the weight of the concrete and sand.
If you make a large turntable, use two 2x4s with a couple of small pieces between as spacers. This would give a much stabler surface to mount the bearing to.
Step 2: The Scrapers
This is the pot I will be making. It is similar to a clay pot.
You will in most cases need a scraper that is the shape of the outside of the pot and one that is the shape of the inside of the pot.
In the first picture of the two scrapers is the scraper for the out side of the pot. I copied this from a clay pot that my wife likes.
The second photo is the scraper for the inside of the pot.
You can make these any shape you like. if you make curves I would suggest you make the outside first and then the inside. The inside curves will have a different radius than the outside. Depending on how large a pot you make will determine the wall thickness and the difference between the inside and outside scrapers.
This small pot needs only a 5/16 inch thick wall. The large pot in the first photo is about 23 inches diameter and has a wall thickness of about 5/8 inch.
Scrapers can be made from many things such as metal, plastic, or any stiff water proof material, I used a piece of siding scrap.
Step 3: Attaching the Scraper to the Turntable
I used a C clamp to fasten the inside scraper to the horizontal on my turntable, and then I attached a metal bar horizontal on to the side of the scraper. This gives the depth of the pot.
Be sure to put the scraper in from the edge of the tile to leave room for the thickness of the pot.
Step 4: Making the Sand Core
The sand core will give you the shape of the inside of your pot.
Use damp sand that is just wet enough to hold together like for making a sand castle.
Start piling the sand and packing it fairly tight. As you turn the turntable the scraper will start giving you the shape of the inside of the pot. I use a small putty knife to add sand as needed to fill in the empty places where the scraper is not touching until you have a uniform shape like the last photo. Carefully remove the scraper so as not to damage the sand. The smoother this is the smoother the inside of your pot will be.
Step 5: The Concrete
Before mixing the concrete attach the scraper for the outside of the pot, along with the bar for the bottom. Leave about 1/4 inch between the scraper and the sand. Some of the sand from the core will be incorporated into the concrete and make the wall slightly thicker.
The concrete is made of two parts sand to one part Portland cement by volume and you do not have to be perfect just close. As with any concrete use protective gear so as not to breath cement dust. And gloves when mixing.
You should always mix the dry ingredients first before adding water. For this project I like to use a 3 lb. cottage cheese container but any small container will work. This will take about 4 cups of sand and 2 cups of cement. Start adding the water and mixing. Add water until you have a paste that is the consistency of soft mashed potatoes. Now take about a third of this and put it into another container that will be easy to pour from. Add water to this and mix. You are looking for a fairly thin mixture about like cake batter or a little thicker than butter milk. I know this will sound weird to concrete people but keep reading.
This is the mixture that will be poured over the sand. As soon as this is poured onto the sand it starts absorbing the excess water from the mixture. This gives you a fairly stiff coating on the sand without disturbing the sand. As you pour and turn the turntable try to get all of the side of the sand covered, If there are small spots left uncovered use the putty knife and drag some of the excess from the bottom up the side to cover these. Do not go from the top down as you will probably pull some of the sand loose. Leave the top of the sand uncovered for now because as the sand absorbs water it will displace air in the sand and it needs a place to escape or it will form a bubble under the concrete some place and mess up the pot. Scrape up the excess concrete from the bottom and put it in with rest of the mixture in the large container. Mix all of the remaining concrete together. Now start applying this to the pot with the putty knife or a small trowel, again apply from the bottom up. As you turn the turntable the scraper will start to form the outside of the pot. You need to scrape up any excess off of the turntable and mix it back into your container.
Once you have the rough shape it is time to cover the top of the sand. Mix some of the cement thin enough to pour and pour it on the top of the sand. it will stiffen up fairly quick as the sand removes the water. Add more cement until you have a complete rough shape. Keep cleaning the scraper with your putty knife as your doing this.
Mix some more thin concrete and pour it over the top as you turn it. It will run down the side as it is turned and help smooth the cement.
The last photo shows the rough shape with the scraper removed. I like to put a small foot on the bottom of the pot. This is done by making a small notch in the part of the scrape that forms the bottom.
Step 6: Smoothing the Pot
Make a small pat of concrete about 1/2 inch thick from any of the sand and cement mixture left. This will be used as a sanding pad later.
Clean off all of the sand left on the turntable. I use a small paint brush. Carefully remove the scraper and wash it to remove all of the sand and cement. Then carefully replace it.
Mix about 3/4 cup of cement with water, this will be the top coat on the concrete. This should be about the thickness of butter milk.
Start pouring this on top of the pot and keep turning. Put on several coats waiting 5 to 10 minutes between. You will see the pot get smoother with each coat. You can also , after you remove the scraper, use a putty knife against the pot as it is turned to smooth it more.
I used a piece of 1/2 inch copper pipe to make the drain hole in the bottom. Twist it as you push it into the bottom. This will remove a core of the concrete that can just be tapped out of the pipe.
The last photo shows the finished pot on the tile and removed from the turn table.
NOW THE HARD PART. This has to sit at least 12 hours or over night.
Step 7: Finishing
After 12 or more hours, turn the pot over with the tile on top. Tap the tile with a piece of wood and it will pop loose leaving the pot full of sand. I scrape off as much of the remaining cement from the tile now as it is still some what soft.
The concrete pot has only partially set or hardened, so it is still kind of fragile. Loosen the sand in the pot with the putty knife and dump it out. You can scrape most of it loose.
Now we will use that pad of concrete we made, along with water, to remove the rest of the sand from inside the pot. It can also be used to take the sharp edge off of the outside of the pot. DO NOT use on the outside surface of the pot. If you do you will remove the top coat that should already be smooth.
Now the pot has to be completely cured. Put it in a container full of water for 7 days. Change the water daily. This will not only cure the concrete but also leech most of the alkaline from the concrete surface. This is important because most plants do not like a high alkaline soil.
After the pot is cured it will be stronger than the same size clay pot. You will find the surface of these pots once cured dry rather quickly as they do not absorb water.
Runner Up in the
Stone Concrete and Cement Contest