Getting yellow out of pearls exposed to cigarette smoke?

[Diamondsareforever]

Is it possible to help get that yellow tinge off a pearl necklace that is from being exposed to cigarette smoke?

 

[Pearl Dreams]

I've never heard of yellowing being reversible.

 

[Diamondsareforever]

I've never heard of yellowing being reversible.

Okay I saw a similar post after reading some last night on here and someone said to leave it out in the sun. Any one done this?