Question about sealing

[SWD]

First, a bit of background:
Home is under two years old, rear patio is a limestone/calcareous, fairly porous, white in color rock. Appears to be a more or less flat rock, locally known as 'flagstone'.
Patio installed with above rock, drains well, standing water not an issue.
Problem:
The installer pressure washed with hot water the rock prior to sealing. Subsequently, the rock has shown a great deal of dis-colorization, some algae and the patio marks very easily. This has appeared about eighteen months after sealing. Homeowner has witnessed the prep work and sealing by patio contractor. However, contractor will not return to correct/address problem.
Activity to date:
I pressure washed with a non heating machine, applied both chlorinated bleach and driveway cleaner (separate applications) and still the patio is a discolored mess.
Question:
Given the above information, how can I return the rock to a uniform appearance?
What kind of sealer/sealing agent should I apply?
Provided those whom answer this post, please include a supplier/website for any chemicals/equipment needed.
Thank you in advance.

[lx665]

Could you post some pictures? Without see it...it sounds like the sealer could have worn off it spots causing color differences.

John

[SWD]

Unfortunately, I do not have a digital camera to post pictures from.
Is there a way to remove the old sealer before applying a different sealer?

[olderthandirt]

Eucho sealer. Apply over whole area then reseal over any of the lighter areas, Since this is a rock its never gonna be exactly same color. If this took 18 months to show up and has alge they have dampness or some kind of a water problem and I would believe that its under the patio where the problem is and its just now working its way through the sealer. jmo


Mac

[Team Gopher]

Hi SWD,

Here is a product I found. Click image for link.

http://www.intlstoneworks.com/product_thumbs/sealngo_s_thumb.jpg (http://www.intlstoneworks.com/products.htm)

"A solvent based impregnator/sealer. Seal & Go ® "S" provides superior stain protection for all natural interior and exterior dense stone, tile, grout, marble, granite, slate, flagstone, limestone, brick and masonry surfaces"

[SWD]

Gopher, I looked at that link you provided.
Thank you, it is exactly what I wanted.