During the renovation of our apartment, I salvaged some of the old doors with the view to reusing them for shelves and other bits of furniture. Below you will find an explanation of the process I went through to make some shelves which I will install into our new inbuilt cupboards.
Step 1: Remove the door hardware, then cut the door panel to the desired dimension of the shelf. If there are some holes in the panel left behind by the handle and keyhole, fill them with whichever small scraps of wood you can find, glue them in and wait for them to dry. Cut the small pieces of wood level with the surface of the door then apply a layer of putty to fill the small gaps. Let this dry and move onto the next step.
In order to fix the shelf to the wall, we will need to, cut and chisel out grooves along the sides of the shelf (these shelves will be side mounted) allowing for the insertion of concealed supports. I find concealing the supports more beautiful than more traditional methods, usually bulky support brackets left exposed.
Here you can see the shelf support, cut to the length of the shelf. For this, I used another piece of timber also salvaged during the renovation.
Press the shelf support down into the panel, to a depth matching the thickness of the support itself. As I have used a hollow core door which is filled with cardboard, it was quite easy to push the shelf support inside the panel.
Add some PVA glue along the line of the cardboard, rendering it more rigid and ensuring that it stays in position and the shelf maintains it's strength.
Clean the edge of the panel which will face the front of the cupboard. A wood chisel and a bit of sandpaper were all I needed to achieve this.
Sand the holes which were previously filled with scraps of wood and wood putty, to obtain a smooth, level surface. The panel is now ready for painting.
Paint the shelves. Here I'm using white spray paint and there are a still few more coats to do.
Here's an example of some shelves which have been painted and installed.
Here's another example of the finished product painted and installed