White patches/swaths in new plaster, cause?

rtilghman

Well-known member
Nov 19, 2014
63
Austin, TX
Had a crack form in our spa after 7 years. Finally got the pool builder to repair it after 1.5 years of back and forth (praise the lord), which involved demoing/concrete patching/replastering the spa (grey NPT quartzscape).

Everything has been mostly fine. However, in the 2-3 weeks it's been curing what look like white brush strokes have started appearing all over the place with varying levels of size and intensity. I've kept the chems at spec (NPT and builder guidelines), haven't used the heater, and have brushed it 2-4 times a day, so I'm certain it's nothing I've done. Does anyone know what these are (photo below)?

IMG_2076.JPG

What research I've done seems to indicate they may be trowel marks? Like, the plaster guy trowel too aggressively too long. I don't have any delaminating plaster or anything, though there was quite a bit of dust the first 4 days or so. Assuming they are late trowel marks, what's the fix? High muriatic with targeted brushing? I'm going to follow-up with the PB, but I'd like to have some idea what's happening before I do. Thanks!

-Rick
 

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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,071
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Try sanding the area with 80/100 grit wet/dry sandpaper. That is much less damaging to the plaster then acid.

Brushing or adjusting water chemistry is not going to make any difference.
 

rtilghman

Well-known member
Nov 19, 2014
63
Austin, TX
That all makes sense (sanding vs acid, not effected by pool chemistry, etc). For some reason I feel like they had to do that (spot sanding) when the pool was originally plastered (spa was originally perfect, pool had some finish issues), but it's hard to remember.

The overarching question I have is "But what are those marks?!?". Are they calcium build-up in late/aggressive trowel marks? Something else? Are they a typical (or fairly common) occurrence with new plaster (quartzscape or other)? I can find lots of research around other issues with plaster (spotting, hazing, delaminating, etc), but for some reason I can't find anything that seems to directly correlate with what I'm seeing. I just want to know wth is going on, both generally and as an input to conversations with the PB.

Fyi, we're in Austin, but on city water, so our calcium is generally fairly high (275-ish ppm). The fact that just the spa was replastered has complicated things a little since I can't isolate that water (it's a Hayward single variable pump set-up), but I've been keeping the PH, alkalinity, and chlorine where it needs to be overall (thankfully the pool water circulating through the spa actually helps mute PH swings in the new spa plaster).

Thanks!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
29,071
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I can't see the marks well in the pics with the reflections.

Probably trowel marks. Hard to say what the cause is. Could be just sloppy work. Could be a poor mix. Could be late troweling. It doesn't really matter why. The fact is they are there and should not be with a quality job.
 

rtilghman

Well-known member
Nov 19, 2014
63
Austin, TX
Thx. Well, I'm in agreement with you about it being sloppy work, and I'm pretty sure it's trowel marks, but I would still like to understand why it happens and is happening. Particularly why it seems to become more apparent with time. I circled one of the largest marks in red on my photo, which should be pretty visible? The darker gray color is what the plaster "should" look like.

IMG_2076.JPG
Thanks,
Rick
 

rtilghman

Well-known member
Nov 19, 2014
63
Austin, TX
Not trying to be difficult, but I'm not really sure how that's necessary? Here is a zoomed in shot of the photo I shared previously with annotations. I mean, it's pretty obvious what I'm talking about... right? It's all over, but that area inside the red circle is a pronounced example. That part is inside of the shadow from me and the fence behind me, and isn't effected by any reflection from the top of the water.

Screen Shot 2021-09-28 at 1.29.33 PM.png
 
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