A thin white film on soap can occur for many different reasons. Complete a Google search, you will a bucket-load of (legitimate) causes: goat milk, ash (lye), air, fragrance PH not geared towards the soap type.
What you do not want to see in a bar of soap: large white blotches, white crumbly patches, large seeping holes, or a dry and delicate soap that crumbles easily. All of these things usually indicate a problem with sodium hydroxide (lye) either not mixed properly in a formula of soap, or included at too high of a percentage. Throw the soap away! Do not use it!
A thin white film on the outer surface of soap is not harmful. Covering a freshly poured batch of soap with plastic wrap for 24-48 hours normally prevents the white film. There are fragrances, essential oils, and soap formulas that are more reactive to air, and despite the soap maker’s best handling procedures, a thin white film can develop on the hardened soap (even after it hits the consumer’s soap dish).
When working with natural base ingredients, soap can be tricky, especially when goat milk is a part of the formula. Milk that is produced from a herd of goats fed on grass, hay, and grain differs in both fat and sugar content from season to season. For this reason, many of us treasure the subtle differences in our soaps. It simply reflects handmade-from-scratch!
Annie’s Goat Hill Handcrafted Soaps – Smell and Feel the Goodness!
Annies Goat Hill Handcrafted Soaps 
Interesting info!
Amy
Thank you, Amy.
Mary, I like your factoid about the fat and sugar content that changes season to season. I had no idea! I love learning about your goat milk soap. I don’t use milk at all but one day I would like to try.
Natural soap, as you know, can be a finicky thing to work with. Let the humidity, or ambient temperature, or the season change, and the soap-maker takes on much-needed changes to accomodate. The same with goat milk that isn’t overly processed before it goes into the soap. This is how I explain it, no two bars of soap may look exactly alike.