Now, since you got rid of the lime and cement, you still need a binder, so how about a good strong one that has no chance of causing efflorescence. Did somebody say epoxy resin? On a trip to Costa Rica in the '90s and touring in the interior we visited a church made up of blocks cut from lava. Being in the interior and not close to the sea and no lime stone or shells I an told they used ege whites for the binder. pat ick -- **Please remember to trim posts, as requested in the Terms of Service** To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: <http://listserv.icors.org/archives/bullamanka-pinheads.html>