Dear Kathy:
You can use Iron-Out as many times as you want: it is safe on natural stone. It may slightly etch polished marble surfaces at times, but it is not something that you should be concerned about with tumble-finished stones.
In order to avoid the possibility that some of the rusty water will get absorbed by your stone, the application of a good-quality impregnating sealer like MB-4 is recommended.
Also very important: monitor your grout and caulk lines regularly and address any possible problem immediately: You don't want any of that water go behind and under your tiles!
May I ask you now to please read and e-sign our Statement of Purpose at:
http://www.marblecleaning.org/purpose.htm?
Ciao and good luck,
Mauri
Article ID: 1004
Created On: Sun, Jan 6, 2008 at 3:25 PM
Last Updated On: Sun, Jan 6, 2008 at 12:00 AM
Authored by: Maurizio Bertoli [mail@mbstone.com]
Online URL: https://marblecleaning.org/knowledgebase/article.php?id=1004