Yesterday I was talking to a plasterer about different finishes and when granite came up he said there was a lot of iron in the mix. We went to his office opened up a bag and ran a magnet over the mix. To my surprise a substantial amount of material was collected with the magnet. What does this mean?
We have pools with this finish that are a couple of years old that have not shown any visible rust issues.
1. Could the iron be locked up in the silica to the point that it won't oxidize?
2. Is it a matter of time before the iron oxidizes, expands and destroys the finish?
3. Is it a matter of what % levels of iron is in the aggregate?
4. Is it correct to assume that iron oxides used to dye the mix would not respond to the magnet?
This is a great site! It would take a day or more of phone messages and return calls to find out answers to questions like this.