Washing a signed top

[FrogFairy]

Son has been to a gig and got his T-shirt signed, but has been sweating.

Please can anyone suggest how to clean the top but preserve the signature?

Sprinkle bicarb on it and leave overnight then put out on the line for a good airing?

Might work.

Sorry it took me so long to respond,, but thanks very much Winky.