As an experiment I decided to try and make an outdoor concrete light. To simplify the light part I used a cheap garden solar light.
Step 1: Making the Mould
To make the shape of the concrete light I built a wooden form from some old wood. I used a lot of screws to make sure the form was strong, this allowed me to get a tight fitting and make sure it wouldn't fail under the weight of the concrete.
The solar lights were then glued to the wood using silicone which I knew would release when it came time to take everything apart.
Step 2: Filling the Mould
Once the silicone was dry and the lights were stuck I started to fill the form with cement. I took this process slow ensuring the lights didn't get knocked off and I was able to fill every part of the form.
As I was filling it I used an electric sander to vibrate the mould and try and help fill to the edges.
I opted for quite a dry mix to avoid lots of water seeping out, in hindsight this was a mistake as I had trouble fully filling the shape.
Step 3: Drying
Once everything was filled I taped up the edges and propped it up ready for drying. In the end I left it a week to dry but even then it wasn't fully cured.
Step 4: Releasing the Mould
Once it was dry I slowly dismantled the form, carefully removing each side so the lights stayed in place.
The light came out a lot better than I was expecting considering it was an experiment, there was one large void which I missed when filling but other than that it looked great.
If I was to repeat this I would make the cement a little wetter so it would fill more evenly and I would also dye it so it didn't look as boring.