With this instructable, you can create your own lighting design for your garden with using concrete. Concrete is a cool material to work with, also a good choice for garden lighting because of the natural look. So just keep reading this instructable and start to create your own concrete lighting. Good luck!

Step 1: The Design

First of all, you need to design a 3d shape. I designed mine in SketchUp based on my earlier sketches. But you need to keep in mind that concrete is a heavy material which is also fragile, so you should be thinking these facts while designing. My design is a triangular prism with another rectangular prism connected to each other and combined into one shape. Spotlights are placed on both top and bottom sides of the rectangular prism.

Step 2: Materials

10 kg’s of cement
10 kg’s of thin sand
7 pieces of wooden boards as listed;

1 x 48x24 cm

24x24 cm

26.8x24 cm

16.8x24 cm

10x24 cm

2 x 15x24 cm

2 x (46 mm radius) spotlights and min. 3 m’s of electricty power cable
20 cm’s of (50 mm radius) plastic pipe
1 m of (10 mm radius) plastic hose
1 pack of soft soap (or any other material to rub inside to the mold, for making mold removal easier after pouring; butter, motor oil etc.)
Various tools for preparing the mixture (a mini shovel, a spatula, a bowl etc.)
Styrofoam cubes (to decrease the weight)

Step 3: Preparing the Mold

After the design process, you have to build a wooden mold shaped as your design. (After the pouring; when you remove the mold your design should appear.) According to the shape (for example for my shape) you should put together the wooden or hardwood boards as shown by the image.

Before putting together the wooden pieces; you should decide where to put the spotlights and drill holes for spotlights’ bodies, accesories and cables. Also another hole for the power cable. (from behind if possible) This step is when you use the pipe and the plastic cable. Because you need to create a tunnel inside the concrete block. Only possible way to do this, is to place the connection before the pouring. Connection and placement of the pipe and the plastic cable are shown by the image. Important: Cut a hole through the midpoint of the pipe and connect the end of the hose to this hole. It will create a space inside which allows you to place both spotlights from sides of rectangular prism and power cable from behind the block.

If you screw the wooden boards to each other, it will be easier to remove after pouring.

The other important thing is, to not to forget rubbing soft soap to inside faces of the mold. It will create a layer between concrete and the mold and removal will be much easier.

Step 4: Preparing the Mixture

According to the volume of your bowl, pour the amount of cement and sand equally. Mix it. After the cement and the sand is completely homogenized, you should start to pour water and keep mixing until the mixture reaches to the correct consistency. The correct consistency is pretty much the same consistency as mayonnaise.

Step 5: Styrofoam Cubes

If you wish, you can cut a few amount of styrofoam cubes to put inside the mold while pouring. Concrete itself is a really heavy material so it is an easy way to decrease the weight. Using a hotwire foam cutter is the easiest way for this. You can also cut different sized cubes for tighter spaces in your mold.

Step 6: Pouring

After the mold and the mixture are ready, it is time for pouring. Make sure you rubbed soft soap inside of the mold and created a layer. This is the easiest part: just pour the mixture into the mold with a spatula. (If you decide to put styrofoam cubes into the concrete block, start placing them insideafter pouring at least 30mm.'s of concrete mixture. You should avoid placing them too close to the surfaces otherwise they will be visible after you remove the mold.)

After pouring, you should wait for 2 days to remove the mold. Concrete block gets completely dry after minimum 15 days, but it starts to dry up from surface to core so waiting for 2 days is enough to remove the mold. Concrete material wants to absorb water while the drying process, so you should pour water on it at least twice a day otherwise it will crack from inside. This is the main problem to avoid.

Step 7: Mold Removal

After waiting for 2 days, your block is dried on the outside. You can remove the mold by using a drill. This is the advantage if you screwed the boards to each other. Next step is to wait for 5 more days, you can observe the change and the color difference through days. Just don't forget to pour water twice a day. 5 days later pouring water won't be necessary and you can start to use the lighting if you want then.

Step 8: Sanding & Flattening Faces

After 5 days, you'll realize the color of the block has changed. It means it is dry enough to use it. For sharp egdes like I designed, you should use a sandpaper to flatten the faces and sharpen the edges. Also you can remove the plastic pipe, you won't need it anymore. You can try to blow into hose from behind and make sure air goes to spotlight holes. Your concrete block is ready for the last step.

Step 9: The Result

Send the power cable in from behind all the way to spotlight holes, connect spotlights to power cable and place the spotlights into holes. Plug it into socket. And that's it! You made your own concrete lighting. All you have to do is carrying it all the way to your garden. Enjoy!