Ilia,

I recently picked up a pre-made putty from a local quarry. Their market for the pre-mix is the renovation market. Anyway, the chemist and the GM at the quarry gave me long dissertations which I mostly didn't understand concerning magnesium in limes used for frescos. Basically statement where, using a hydrated lime from the US in the Ohio River Valley for making putties rather then chunk lime negates concerns about magnesium. The lime is geologically much older and the kiln slaking reduces the magesium to a filler\binder and has no adverse chemical reaction to fresco work. Their opinions seemed to be backed up with research on their quarries product. Any opinions? Don C.