New Black-dyed Plaster turning White ??

[TamTam444]

Seeking...information/answers/guidance...

We have a client that had his pool replastered 3 months ago (not by us) with standard 'marble dust plaster' with Jet Black dye added. Initial results - beautiful. The initial start-up was done correctly and carried out without incident.
There is a 'white film' over the entire surface, & progressively getting worse (whiter). We drained the spa and did a 'light acid wash' on it which removed the 'white' completely & it looked great! (also little bit of the color - not too bad, though). 3 days later, the white is back or coming back.
We would like to know if anyone has heard of this or know what could be causing it? ...and if so, how we might stop 'the white' or correct what's causing it. By checking the spa 1st, we know that draining the whole pool for a light acid wash is not the answer.

These are the only readings I have at the moment.....(hoping it'll be sufficient to start)

Chl 3.0
pH 7.6
Alk 100
CY 70
CH 325 (high & has been since ~day 3...(highest reading was 370-2wks after replaster)

Thanks!
Tammi

 

[duraleigh]

Hi, Tammi,

That's a tough one. While the numbers don't really indicate it, I might suspect it is calcium scale.

I would drop the pH down to 7.0 - 7.2 and hold it there. Hopefully, that will stop it and perhaps even start to slowly reverse it. In any case, it's a cheap and harmless attempt.

 

[257WbyMag]

What duraleigh said to do makes sense. Hopefully it helps. I think that those black plaster pools are really incredible looking.

 

[onBalance]

It could be calcium scale as Duraleigh stated. But there are other possibilities.

Could be the wrong kind of black dye for pool plaster. Organic dyes don't hold up well. Inorganic dye is better.
Could be from adding too much calcium chloride to the plaster mix. That can lighter the color over time. And wet troweling can also cause a lighter color to develop in time. Manufacturers advised against doing either.

Remember that white cement is generally used for mixing with a black dye added to it.
If the "white problem" is due to these issues, there isn't much you can do to fix it.

 

[brg88tx]

i wonder why anyone would want a black pool in the houston area. summertime water temps will be over 100.