I did some try outs with http://www.modernistpantry.com/gellan-kelcogel-lt100.html
A new cleaning method. You may read more here: http://www.hindawi.com/journals/ac/2014/385674/
Overall the effect was not as dramatic as using bleach/submersion. The everyday modern poster collector probably not so excited with results.
This would be more geared for extremely fragile/historical/ irreplaceable paper artifacts.
I do see a potential tweak and use as a type of gel backing.