A particle with large electric charge Z (Z ≫ 1) and radius R0 inserted into plasma is surrounded by a plasma shell, which is stable to weak and short-term external exposures. As a result, during experiments the particle can reveal an effective charge Z* lower than the true one (Z* ≤ Z), and an effective radius R* larger than the true one (R* ≥ R0). The effective electric charge and the effective radius of a water droplet in a dropwise cluster have been calculated using the Poisson-Boltzmann equation. It has been recognized that these parameters are not the function of a droplet's true charge, but are the function of a droplet's true size and the Debye's radius of the plasma. Experimental data on the droplet properties in a dropwise cluster have been explained.