We made sure to perform this experiment on a dry day because dry days tend to produce much better results. Excess moisture in the air will prevent a charge from building up because electricity is able to escape into humid air, or air that has a lot of water vapor in it.
Let’s think about why we constructed our electroscope the way we did. We’ll start with why we coiled the copper wire: we did this because we wanted to create a lot of surface area for electrostatic induction—the transfer of electrons from one surface to another without touching. The more area there is for electrons from our object to enter the wire, the faster energy will flow down into our electroscope. This is also why thicker wire is better: the bigger the radius of the wire, the more room electrons have to move.