I was reminded recently of my first steps in bonsai pot making was actually many years ago. While it has only been more recently that I've ventured into ceramics that first step was taken with concrete.
So I've been out to scout around and find those old pots. I was pretty sure some were hiding in one of my 'boneyards' around the place and sure enough there they were covered in a age of decaying eucalyptus leaves. We've been here for 10 years and so these pots must be at least 15 years old, made at a time when my trees were smaller and so the pots are of a fairly modest size.
This model is about 250mm long. I recall looking for some way to get some shape into the wall design and hit upon using timber skirting board. It comes in a variety of profiles and height, ideal for making moulds like this. I simply mitred up four pieces and used a piece of wire to hold it all together and in shape. The concrete mix was about 3 coarse sand to 1 cement and only just enough water to moisten the mix, with no 'free' water. After oiling the mold then, bit by bit then I rammed the mix into the mold - floor and walls and then smoothed off the inside. After a very short time it was strong enough to take out and immerse in a container of water. As they say concrete continues to get harder and harder over time. As I recall most things would grow in these pots, well except azaleas which prefer acid to alkaline conditions.
This is a detail of the feet which were set in place as soon as the pot was released from the mold.
This one was a little more ambitious. To make this mold I used a bonsai pot I had and coated it with many layers of casting latex, then a concrete surround to support the latex. Reverse that when set and follow the same rammed concrete procedure, into the latex mold. The mold included the feet so did the whole job in one go.
The latex is never going to work with clay but anyone looking for an easy way to make a ceramic pot mould might like to try timber. You can also add all sorts of things to a cement mix, like poplystyrene particles to lighten the material, which would be great if you needed a big grow pot. Leaving a pot immersed in water for a good period will get rid of most of the alkalinity that will initially come out of the concrete.
So I've been out to scout around and find those old pots. I was pretty sure some were hiding in one of my 'boneyards' around the place and sure enough there they were covered in a age of decaying eucalyptus leaves. We've been here for 10 years and so these pots must be at least 15 years old, made at a time when my trees were smaller and so the pots are of a fairly modest size.
This model is about 250mm long. I recall looking for some way to get some shape into the wall design and hit upon using timber skirting board. It comes in a variety of profiles and height, ideal for making moulds like this. I simply mitred up four pieces and used a piece of wire to hold it all together and in shape. The concrete mix was about 3 coarse sand to 1 cement and only just enough water to moisten the mix, with no 'free' water. After oiling the mold then, bit by bit then I rammed the mix into the mold - floor and walls and then smoothed off the inside. After a very short time it was strong enough to take out and immerse in a container of water. As they say concrete continues to get harder and harder over time. As I recall most things would grow in these pots, well except azaleas which prefer acid to alkaline conditions.
This is a detail of the feet which were set in place as soon as the pot was released from the mold.
This one was a little more ambitious. To make this mold I used a bonsai pot I had and coated it with many layers of casting latex, then a concrete surround to support the latex. Reverse that when set and follow the same rammed concrete procedure, into the latex mold. The mold included the feet so did the whole job in one go.
The latex is never going to work with clay but anyone looking for an easy way to make a ceramic pot mould might like to try timber. You can also add all sorts of things to a cement mix, like poplystyrene particles to lighten the material, which would be great if you needed a big grow pot. Leaving a pot immersed in water for a good period will get rid of most of the alkalinity that will initially come out of the concrete.
Concrete bonsai pots are still very popular in some traditions and tribes. I saw them in many parts of the world but off course the shape differs a bit.
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