Buy a quart of 90% general purpose alcohol soak the gloves in a quart jar with
the lid on for 30 minutes, shaking the jar a few times.
Remove gloves wring out and soak in warm water containing borax and dishwater soap
a strongish solution that feels 'slick' to the touch.
work them around for a while then rinse in warm water and hang up to dry slowly.
Before they are completely dry i.e. not hard and stiff, put them on and start
working in small amounts of neatsfoot oil continuing to wear them until they are
95% dry..
That should restore them somewhat.*
* If these gloves are goat deer or elk skin, the recovery will be much more
impressive than if they are pig or cow skin. Since you didn't mention the kind of
leather they were, I thought you should know.
--
CK