Global Administrator wrote: ↑30 Aug 2020 20:10.
Paper physical dimensions size might alter by a tiny fraction of a mm after any soaking. Impossible to measure it.
As outlined clearly above SIZING is an additive to the stamp paper.
Every amateur alchemist witch-doctor who bleaches and fiddles and otherwise degrades stamp paper loses or decreases that sizing, with each mad hatter experiment. Do it several times, and you have a limp and sad and faded blotting paper quality, sad mush.
Their stamps - they can cut them into pieces if they choose or dip them into tar etc. Seems a shame though.
Hot topic Sheriff!
In book binding we bathe very old papers with distilled water, sometimes chemicals are introduced, like ethanol, liquid Mylar, et al, in extreme cases, to rinse off debris.
Unless one is a paper restoration specialist the question is rudimentary to me. I.e. your comment that the patinas are preferred to a "cleaned" paper (or coin). I conserve old documents & I can tell you yes, foxing is a problem. One never tries to do anything other than CONSERVE.
This usually means removing dirt, grime, etc., & leaves the document as "original" as possible. That stated, conserved papers, that finish brighter, are not necessarily frowned upon, unless chemically induced. Papers ARE different, requiring different techniques for each, & sizing is a relatively new process.
Old papers often come out "brighter" after common (water) cleansing. Anything that takes away ANY of the original is generally a conservation "No-No" unless it is detrimental to the piece, such as acidic gums, etc.
If there is an element that IS a detriment & can't be removed, every effort is spent in SLOWING the process of degradation.
Having gum definitely throws a "don't touch" into the mix. I would caution anyone attempting any type of "conservation / cleaning." Any good paper conservationist will "ditto" the above.