Joined: July 2004
||Posted: 09 May 2019,16:30
Very, *very* useful images, but I wouldn't take them as definitive proof that use of either (or even any) sealant will definitely prevent staining from bedding or jointing during installation.
Following on from the sealant trials on sandstone 3-4 years ago, I had planned to look next at how pre-sealing popular stones (I considered G603 granite, Fossil Mint, Forest Brown, Kaddapha Yellow) could minimise jointing stains from four different mortars: hand-pointed sand/cement, proprietary cement slurry, 1-part polymeric resin mortar, and a 2-part resin slurry mortar. Then it dawned on me just how much space was needed to acommodate the samples for the 6-12 month run period of the trial....and I just don't have that much garden or shed-roof to spare!
I asked a mate with a sizable yard, and he said he'd help, but then we got distracted by all sorts of other projects and it's never been so much as started, although I do have some of teh sample pieces. I won't have time to set it up this summer, as I'm knee deep in the website re-build, but maybe next year....???
Anyway, the point is that I've had too many reports, and visited a number of sites, where pre-seled paving has been stained by either the bedding, the jointing, or both, during the installation, and I wanted to find out how it was happening, and, if possible, why it was happening. So far, I've not detected a common thread - I can't say it's such-and-such a sealant, or such-and-such a mortar, but....and finally I come to the point.....it does seem that water-based sealants are a greater risk.
So: I'd be madly keen to hear how you get on, and if you encounter any problems, as it could help define a trial for 2020 or later, perhaps.
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