Ko-Cho-Line. I once knew a Deputy Director of Leicestershire Museums. He swore by it. For just what you have as your issue. But as DALUA says what Carr Day & Martin don't know about leather isn't worth knowing, give them a call.
Ko-Cho-Line Leather Dressing from Carr & Day & Martin protects leather from mould and mildew when in storage. Click now.
www.carrdaymartin.co.uk