Replies

1. 
   steve | Mar 19, 2004 02:45am | #1

   that is a weird one!!

   trying to remember some long lost chemistry, and i believe the limestone is predominantly calcium carbonate and that combined with water may produce a very weak acid or base, and that would corrode your aluminum straight edges and leave a stain which would be aluminum carbonate

   dont quote me on any of this, but thats my theory

   any other ideas anyone? im probably on the right track, maybe wrong  chemistry, but sounds like a very minor corrosion of the aluminum

   caulking is not a piece of trim

1. 
   brownbagg | Mar 19, 2004 03:01am | #2

   let take it one more step. Aluminum and concrete does not mix, its create a chemical reaction. would limestone and concrete be made up of the same cheical conpound

1. 
   steve | Mar 19, 2004 03:11am | #3

   they certainly are, cement is predominately lime

   what "limestone" is exactly, i dont know, i'll try a search and report backcaulking is not a piece of trim

1. 
   steve | Mar 19, 2004 03:23am | #4

   check out http://www.aldonchem.com they seem to have lots of good infocaulking is not a piece of trim

2. 
   HeavyDuty | Mar 19, 2004 04:31am | #5

   Steve, your reasoning sounds right. Limestone is CaCo3, remember stalactite and stalagmite? Basically the moisture on the surface of the tiles dissolves a minute amount of CaCo3 to form H2Co3 which is a weak acid, and you told the rest of the story. I never thought it would happen overnight though.

   Edited 3/18/2004 9:36 pm ET by TOMCHARK

2. 
   HeavyDuty | Mar 19, 2004 04:38am | #6

   How did you rehone the tiles? Did it match the original finish reasonably well?

1. 
   ycsifmh | Mar 20, 2004 02:00am | #9

   Thanks to you and the others for your help.  I rehoned the tiles with some diamond abrasive pads my boss recently purchased, and a little bit of elbow grease (and water).  The problem, of course is you cant see what your doing, or how it will look until it dries.  I had a good look today and the match is pretty good, except for one tile that came out blotchy, I guess I'll hit that again.

   I think I could solve all my problems by enhancing the tile and darkening them all to a uniform color.  The client likes the idea of enhancer, but I must have the wrong stuff, 'cause I put 6 coats on a sample piece and it just sucked it up and dried back to its original pale gray.

   I've never seen anything like this stuff, and I thought glass mosaic was tough!

3. 
   steve | Mar 19, 2004 06:30am | #7

   tom seems to have the right answer, CaCO3 is calcium cabonate and the resulting acid is carbonic acid

   aluminum is very reactive with acids as are all metals but aluminum is more so than most

   the resulting white stain would be aluminum carbonate, a salt from the acid/metal reaction

   interesting situation, i'm sure that most of us would never anticipate it

   caulking is not a piece of trim

4. 
   ANDYBUILD | Mar 19, 2004 04:17pm | #8

   I installed a lot of large white limestone tiles on an entry floor in my last house.

   What a pain it is to try and get stains out before I sealed it.

   I tried everything from poultice mixes to bleach to no avail.

   I'd never use it again...at least not in white.

   I thought about sealing each tile before I laid it down but wondered if that'd lock in the moisture of the thinset/mud and cause worse damage.

   Anyway.....glad that phase is history.

   Be well

                  andy

   "My life is my practice"