Soap is Sweating
I make a basic soap with olive oil, vegetable oil, tallow, coconut oil and fragrance oils but after about 4 weeks it starts sweating.
I live in Idaho so humidity isn't the issue and I don't use melt and pour soap base.
Handmade soap contains glycerine which is a humectant and it will draw to it whatever moisture that is in the air.
Our homes often contain quite a bit of moisture from cooking, washing and showering. This moisture can find it's way onto your soap which is why it is important to pick a storage spot carefully.
My favourite method for storing soap is to line a box with paper towel and place the soap bars, not touching each other, in a single layer.
The box should be stored away from places like the kitchen or bathroom. The best spot is one that is cool, dry (not damp) and away from direct sunlight. A closet in your home that is not on an exterior wall is ideal.
You can also purchase silica gel packages and place them in the closet or box if the above isn't enough to stop the soap from sweating.
Silica gel packages can be purchased on-line from Amazon and are quite inexpensive, usually only a few dollars. They should effectively absorb any excess moisture keeping your soap dry.