When the solid has a high affinity for water - in which case it is called hydrophilic (high energy e.g. glass)- water spreads. In the opposite case of hydrophobic (low energy e.g. teflon) surfaces, water does not spread but, instead, forms at equilibrium a spherical cap resting on the substrate with a 'contact angle'.
Infections such as trichomoniasis, gonorrhea, and Chlamydia (all STDs); and yeast infection can all cause vaginal discharge. Vaginal discharge can be associated with other symptoms such as burning or itching. Antibiotics are given for infections that cause vaginal discharge.
Vaginal discharge with bacterial vaginosis will be gray, white or yellow. It will also have a fishy odor. If you have gonorrhea, you might have a cloudy or yellow discharge. Yeast infections can be apparent if you have a thick, white discharge. This discharge is often described as having a cottage cheese consistency.