To know how smooth is enough for the capacitor that I will be making I decided to take a real capacitor plate as a reference (visual) as shown in the fig
Now talking about the shape of the cap I have chosen to go with the circle shape with R = 1.5 for the first cap and R = 2.55, and the reason for
that is simple, generally speaking, the circle shape got more uniform filed lines, a square shape cap got more sharp corners which lead to more distortions in the filed lines.
# The material Preparation and making steps:
The first step was prepare the material and solving the roughness issue, the way I did that was by rubbing the aluminium foil gently to hard level with soft cloth which I used on it acetone, and because the acetone is an organic solvent and won’t attack metals, including aluminium. Which was the purpose for it is clearing dirt on the aluminium. So after doing that several times I started taking pic for the aluminium surface and the cap surface to compare on a different magnifications from X104 to X2540, as shown below: