Extraction question! Film?

[Spiritesseract]

I'm currently doing a vinegar water boil with mhrb. About 10 minutes into the light boil, I notice a film being created on the top of the water. It is as if you spray paint onto water if you've ever done that. Is this normal?

 

[Parshvik Chintan]

i have noticed it on every potent brew i have made, with or without acid.

 

[Spiritesseract]

Thanks for the peace of mind