Custom icons for individual files revert to default upon restart
I added custom icons for several of my most-used spreadsheets by using the Get Info --> copy png in Preview --> paste png method. These are custom icons for specific files; I am not looking to replace the default application icons. They look like this:
When I work in one of these files, save, and restart my computer, the custom Excel icons revert to defaults:
Most discussions I've found RE: icon customization have to do with altering the application defaults and icns files, not with simple individual file customization. Has anyone experienced this? What am I missing?
Thanks!
OSX Mountain Lion 10.8.5, MacBook Air 2013, 1.3 GHz Intel Core i5, 4 GB 1600 MHZ DDR3