Salt water

The salt water bottle capacitor is about the easiest type of cap to make. This one is rated at 5.36nF.We use two banks of bottle caps for the correct tank circuit capacitance. The caps are then connected in parallel.

To build one like this all you need is.

Plastic box which will hold 12 or so bottles
12 one pint bottles
Salt water.
Oil
Two long bolts for the plate connectors.
20mm*40mm wood to made a small frame for the bottles to stand on
Thick copper wire for the bottle connections.

METHOD

Once you have cut the holes in the top and made a stand for the bottles.
Place the bottles in the box and fill with salt water (leaving about 3" gap at the top. now pour about 1/2 -3/4 of an inch of oil on top of the water to stop corona loss.
Now fill the bottles with salt water (Note the water level in the bottles should be the same as the level in the box) now top off the bottles with oil.
Insert copper wire in the top of the bottles (Do not let it touch the bottom of the bottle leave about 1" gap ) now connect all the bottles together.
The water in the bottles form one plate of the cap and the water in the box is the other so the glass acts as the dielectric. The wooden frame in the bottom of the box just supports the bottles.
One of the main advantages of this type of cap is that you don't need exotic components to build one.