Diamondbrite finish color issues in new pool

[tohughes76]

I'm looking for advice regarding color issues with my pool's Diamondbrite finish, which was completed in March of this year. The finish is Cobalt from the watercolors series which is a mix of 60% midnight blue and 40% onyx. After the initial filling of the pool, it looked blue as expected prior to exposing the aggregate with an acid bath under supervision of a pool tech. Once the aggregate was exposed after a few days the levels were brought back to normal, and I have maintained them since using the TFP recommendations for a SWG plaster pool. From the time the pool was opened, I have felt like the finish was way too dark-leaning much more to the onyx color than the blue of the cobalt sample. You can see from the picture below, especially on the tanning ledge, how finish favors the onyx and gives the water a green hue instead of blue:






A few days ago, however, we made an interesting discovery. An overhanging tree dropped some debris onto one of the ledges in the pool which created a stubborn stain. After about an hour of scrubbing with a nylon brush and removing the stain, we created a spot that looked like the cobalt sample shown above:



Is there anyone here in TFP that has experienced anything like this with a quartz finish? Is it possible that even though the aggregate is exposed that the dark color is still plaster that has to be removed to get to the true finish? I talked with a customer service rep from SGM who didn't seem to feel this was normal, but suggested doing another acid bath. His recommendation was to drop pH to 7.0, add a sequestering agent & start brushing again. I would definitely need to use acid as brushing alone would take forever given how long it took to expose that spot, but i'm not sure that 7.0 is aggressive enough to help.

Any suggestions here would be appreciated!

 

[onBalance]

Try a test by lightly sanding using 100-grit wet/dry sandpaper on a small area.

 

[tohughes76]

Thanks for the suggestion. I tried two spots using both wet/dry sandpaper and scotch brite, both exposed more of the blue finish in about 1/4 of the time it took with a nylon brush. Do you think an acid bath with brushing would achieve the same results for the whole pool?

 

[onBalance]

I don't think an acid bath will make much improvement, and more importantly, doing that will etch and perhaps make the surface rougher to the touch depending on how much acid is used. And that, unfortunately, will "age" your pool by a couple of years.
Also, etching the plaster surface will just invite more discoloration over time.

 

[tohughes76]

Unfortunately wet sanding the entire surface of the pool would probably take months as labor intensive as that is, not to mention it would be hard to get the pressure I would need using a pole for the deep end. Short of draining the pool and using an orbital sander, I don't see where I have any other reasonable option to remove this layer.

The rep suggested taking the pH to 7.0...do you think that would be acidic enough to allow me to brush this layer off without getting too low? The acid baths that I have read about are taking the water down below 6.0 which would likely have the long term effects you are talking about.

 

[onBalance]

If the white discoloration problem all over the pool is actually scale, it is unlikely that a pH of 7.0 will do much. But perhaps in time it could be removed with vigorous brushing.

But there is also the possibility that the white discoloration is not scale, and simply some plaster areas that are porous (due to improper practices), which results in a dark color plaster/quartz finish turning whitish. If that is the case, then making the water aggressive will just make the whole problem worse.

And then there is another possibility that the "blue" pigment is being bleached out by the chlorine, and leaving the "onyx" color as the dominant color. There is an expensive "blue" pigment that won't bleach out, but unfortunately, the cheaper type can be bleached.

 

[tohughes76]

Fortunately there is no white discoloration problem at all, just the color being more onyx than blue.

The SGM rep suggested trying one of those spot remover brushes with the acid reservoir on a test area to see if that exposes the color prior to an acid bath. Not sure if using that with the 16% acid would be harder on the finish than lowering the ph to brush it out. I suppose it is worth a try...just ordered the out spot tool and will see what happens.

 

[onBalance]

If the blue pigment is being bleached out by the chlorine and fades, then understand that as the underlying blue color pigment is exposed by the acid treatment, the blue color may soon become bleached and fade again in time and onyx color will be the final result.

 

[tohughes76]

I think my next step is to try using one of the hybrid nylon/wire pole brushes to see if that will work in the same way as the sandpaper. Hopefully the hybrid brush will be easier on the surface than a straight wire brush. If that does work, I would be able to do the entire pool using that over the next few weeks without changing the chemistry.