WillL, it's empiric information: they all print well with Cyanotype? (That's our actual subject right?) BTW, some print well with Argyrotype and New Cyanotype too - the most finicky processes when it comes to paper choice... In any case, a 1-3% HCl bath for 2-5 minutes and a good rinse (3-5 water changes, 10-15 minutes...) will take care of calcium carbonate buffer for sure, BUT with the expense of decreasing the paper's longevity. (By the action of HCl severing some bonds within the cellulose structure - the longer the treatment, the more serious the damage will be.)

Can't you request a sample from the batch, before committing for such a big amount of (155 square meters; equiv. to 155 A0 / 620 A2 sheets!!!) paper?

Regards,
Loris.