That "white bloom" also just might be _stearates_, a usual
component of leather dressings, exuding.

According to [log in to unmask]:
>
> We have in our collection leather bridles, halters, reins, saddles,
> saddlebags and so forth that have a white "bloom," which I'm assuming is
> mold. It wipes clean, and I've used basic saddle soap which also removes
> the film. The items are stored in a climate controlled HVAC building, but
> I'm wondering if there isn't enough air circulation. Has anyone else had
> this problem?
> Please, no lectures about calling conservators. This is just a topic for
> conservation and feedback.
> Thanks.
>