Joined: July 2004
||Posted: 09 July 2019,10:58
I can see reflective staining in at least one of your images.
Unless the whole of the flag underside is primed with a suitable slurry, and then laid on a full bed, there is a risk of reflective staining. A primer alone will NOT prevent spot bedding marking the flags.
And a sealant would only seal-in the problem, not fix it.
Joint It, like so many of the one-part polymeric mortars, uses a doping oil to prevent curing of the resin coating applied to the fine aggregate. Fust which oil is used to dope will determine how badly any staining will appear to be. Some are pretty bloody awful, while others are barely noticeable, and, of course, the substrate has a huge part in how it all looks.
The good news is that most of these doping oils weather out in 2-24 weeks, so *that* part of the staining will, eventually, dissipate, but the reflective staining is more likely to be permanent.
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