Affect of shellac on a signed baseball

[Topnotchsy]

I'm pretty new to the vintage and signed baseball markets but I've noticed that many auction house listings mention that the signatures on a given item were preserved under a layer of shellac. In some cases the ball appears pretty browned, but other times it appears to be pretty close to white.

I was wondering how shellac was viewed by collectors? Are signatures with the same "grade" valued differently if one is on a ball that has shellac? Is it more a matter of aesthetics when it comes to coloring? Is there anything else worth knowing?

Also, does a layer of shellac mean there is less of a concern about fading and sunlight? I have the balls displayed in a place where they get no direct sunlight, (and in general not a ton of light) but definitely don't want an 60-90 year old item to fade because I was careless.

Any help is very much appreciated! After being a fan of baseball for a long time I've ventured into this world knowing very little, and this board has been a huge help.