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Thread: White Spotting of New Plaster Pools

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    White Spotting of New Plaster Pools

    The problem of plaster spotting has been an ongoing puzzle and controversy in the swimming pool industry for over three decades. The generally round, smooth-yet-unsightly white soft spots in new plaster pools have long been a source of contention among pool plasterers, and pool chemical service firms or pool owners, each blaming the other for the phenomenon.

    From 1999 to 2003, onBalance provided several case studies to the plastering industry (performed by two respected cement labs) on white spotting (which some incorrectly name it "spot etching"). It was determined that white spotting was caused by several contributory elements, all due to improper plastering practices: too much calcium chloride added as a set accelerant; adding water to the hardening plaster surface; trowel-pressing the added water into the surface, creating porosity and micro-cracking in localized areas or spots, allowing for later water penetration deep into the plaster matrix; subsequent “rinsing” (non-aggressive leaching) of soluble plaster components (calcium hydroxide and calcium chloride) from the thus-compromised surface, and late hard troweling.

    Over the course of the past year, onBalance undertook an additional project to help provide more definitive and sufficient evidence as to the cause.

    A one year old spotted pool in Los Angeles was inspected by both an onBalance partner and by a pool plastering industry advocate (who incorrectly describes it as "spot etching" or "etching deterioration.") Both had produced written opinions on the pool in question, with the former implicating defective plastering workmanship and the latter implicating aggressive water chemistry.



    At that point, onBalance drained the pool, and with representatives of the trade press, service members, and pool plasterers present, core sampled the pool, obtaining dozens of cores from a local area of a spotted pool wall. These samples were sent to four different cement failure-analysis laboratories for petrographic examination. Results have been obtained from Construction Technologies Laboratories (a subsidiary of the Portland Cement Association), the RJ Lee Group, Riverbend Petrographics, and Wiss, Janney, Elstner. Would these highly respected labs find consensus when independently analyzing plaster cores containing white spots from the same pool?

    All four labs have now submitted reports on their analysis. Here is a summary of their findings:
    1. The pool plaster contained more than 3 percent calcium chloride dehydrate, which is detrimental. (The allowable maximum is two percent, and zero for colored plaster).
    2. The whitish spots were smooth to the touch, but under a microscope, the spots were shown to be porous, permeable, structurally weak and soft, with an abundance of micro-cracking and a high water-to-cement ratio.
    3. The depth of the micro-cracking and porosity within the spots went as deep as 5 mm (.2 in. or 3/16th) and a diameter (width) of 15 mm (.6 in.)
    4. The unaffected surface (cement paste) surrounding the spots was dense, hard, and smooth, and did not have a high water-to-cement ratio, the porosity, or the micro-cracking as found in the spots.
    5. There was no evidence of aggressive water or chemical attack (relative to calcium carbonate) causing the spots. The surface surrounding the spots was not etched, but instead had been “carbonated” which provided further evidence that the surface had not been etched by aggressive water.
    6. The improper adding of water during plaster finishing (troweling) causes excess porosity and micro-cracking within the spots. This in turn, provides an avenue (breach) for pool water to penetrate deeper into the plaster matrix and access soluble compounds causing continued loss of plaster material.

    As indicated above, improper water chemistry did not cause the white spotting, and therefore, it should not be called "spot etching" or "etching deterioration." In fact, balanced pool water – and even water with a positive CSI value – will not stop this process from happening to a defective plaster surface. And depending on the severity of the improper plastering practices, spotting may occur within a week, but usually not until a few months down the road.

    White spots have a smooth, yet porous surface. This is due to the loss of two soluble plaster components (calcium chloride and calcium hydroxide which comprise of about 15 – 20 percent of the cement) interspersed throughout the more durable materials. This results in a weakened, soft, and self-deteriorating surface. Porosity, and subsequent carbonation, creates a lighter (whiter) color in contrast to the surrounding denser and unaffected plaster surface.

    While white soft spotting is somewhat visible in white plaster pools, it becomes more unsightly when the surrounding surface is off-white and slightly gray due to excess calcium chloride being added to the plaster mix. And since the spots are more porous than the surrounding plaster, it can also absorb copper or iron and become aqua or brown instead of white. Spotting is especially visible and objectionable when it occurs in dark colored plaster and colored quartz pools.

    By comparison, aggressive water attacks and removes most plaster compounds from a dense and smooth surface, thereby causing a uniformly etched and roughened surface, similar to fine sandpaper, and with no significant change in color. As is known, when dark colored plaster pools are given various types of acid treatments, they do not turn white, nor do they spot.

    The plastering industry has no study that proves that aggressive water causes random white spotting (or spot etching) on quality pool plaster. There seems to be little doubt that the cause of plaster spotting has been discovered, analyzed, identified and documented. See these threads: How White Pool Plaster Turns Blotchy
    High CYA Levels Do Not Stain Plaster

    For more information, see the following post: Being Blamed for Plaster Discolorations? Don't Get Hoodwinked
    scientific-evidence-on-plaster-spotting-t57853.html
    And: aggressive-water-versus-improper-pool-plastering-t51900.html
    For proper plastering practices, see this post: ten-guidelines-for-quality-pool-plaster-t42957.html



    For another helpful picture of white spotting, see this thread: http://www.troublefreepool.com/threa...714#post690714
    Last edited by onBalance; 07-07-2017 at 05:56 PM. Reason: To address the false term "spot etching" and "etching deterioration."

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    Re: White Spotting of New Plaster Pools

    Below are photos of white soft spotting on black or colored pool plaster.
    The white spotting in these pools is not calcium scale. The white spots (which some plasterers incorrectly name it "spot etching") are smooth to the touch and are not removed by casual sanding or by performing an acid wash treatment.
    Severe white spotting can cause the calcium hardness level of the pool water to increase, and does that through the process of the plaster surface deteriorating and dissolving plaster material into the water even though the pool water is balanced. The result is a soft and porous plaster surface and the dark color plaster turning whitish in spots, streaks, or in blotchy patterns, which is caused by poor workmanship practices as mentioned above in my original post.


    HOlson5copy.jpg

    Haro11.jpg

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    Re: White Spotting of New Plaster Pools

    Thats exactly what I experienced with this pool. At just over a year old and a denied warranty from both the builder and plasterer...they said there is no warranty on color! This was a very dark gray plaster that had mostly faded and instead of the white areas being the distractor, the dark areas where color still remained made the rest of the pool look bad.

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    Re: White Spotting of New Plaster Pools

    There may be way to get the plasterer to warranty that poor plaster job. And that is on the basis that they may have used calcium chloride in their colored plaster mix.
    Most color pigments manufacturers state to "not use calcium chloride with their products" and will cause color fading and blotchiness. An analysis of the plaster can be performed and used to prove that calcium chloride was used, and should not have been.

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    Re: White Spotting of New Plaster Pools

    I'm certain calcium was used and that definitely looks like the culprit. Regardless, the warranty claim was denied.

    I ended up fixing it...

    IMG952061.jpg

    IMG_20161101_111503867.jpg
    -Brian-
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    Re: White Spotting of New Plaster Pools

    Quote Originally Posted by bdavis466 View Post
    I'm certain calcium was used and that definitely looks like the culprit. Regardless, the warranty claim was denied.

    I ended up fixing it...

    IMG952061.jpg

    IMG_20161101_111503867.jpg
    Oh wow!! Did you do what I think you did?

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    Re: White Spotting of New Plaster Pools

    A classic onBalance post that really needs to be part of Pool School!!

    Brian, nice fix to a lousy plaster job. Aside from the pool owner losing money on the original interior finish, I bet they will be very happy with the results you have provided for them.

    Here's my question - exactly how do you "prove" anything when it comes to plaster?? Is there a simple process where an individual homeowner/pool owner can get a poor quality plaster surface analyzed independently? Exactly how do you go about doing that?

    We often get members on here with lousy cement work done, either decks or pool shells or plaster surfaces. It would be nice if TFP could provide an informative guide on how an independent 3rd party can be brought in to evaluate a job that is highly suspect. We often see posts where folks are told to go to the mat with the PB but we all know that the pool owners neither have the expertise to argue against the well-rehearsed excuses a PB or plasterer will use nor do they usually have much financial or legal leverage in this situation.

    How can TFP provide them with a process for getting the proof needed in order to be taken seriously?
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    Re: White Spotting of New Plaster Pools

    Quote Originally Posted by JoyfulNoise View Post
    A classic onBalance post that really needs to be part of Pool School!!

    Brian, nice fix to a lousy plaster job. Aside from the pool owner losing money on the original interior finish, I bet they will be very happy with the results you have provided for them.

    Here's my question - exactly how do you "prove" anything when it comes to plaster?? Is there a simple process where an individual homeowner/pool owner can get a poor quality plaster surface analyzed independently? Exactly how do you go about doing that?

    We often get members on here with lousy cement work done, either decks or pool shells or plaster surfaces. It would be nice if TFP could provide an informative guide on how an independent 3rd party can be brought in to evaluate a job that is highly suspect. We often see posts where folks are told to go to the mat with the PB but we all know that the pool owners neither have the expertise to argue against the well-rehearsed excuses a PB or plasterer will use nor do they usually have much financial or legal leverage in this situation.

    How can TFP provide them with a process for getting the proof needed in order to be taken seriously?
    SPOT ON JOYFULNOISE ! ------------> Here's my question - exactly how do you "prove" anything when it comes to plaster??


    That is exactly what I was thinking! Do I obtain a sample of my plaster and is there anything I can do to test for the calcium?
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    Re: White Spotting of New Plaster Pools

    JN, it is unfortunate that with plaster defective issues such as what this post identifies, can involve a lot money and work. To properly determine and prove the cause of a particular pool's white soft spotting discoloration, a plaster core (3 inch diameter) would have to be removed from the pool and sent to a cement petrographer for analysis and would cost about $1500. Obviously, the taking of a plaster core results in an unsightly patch in the plaster.

    Fortunately, there is the option strategy of having a cement lab ONLY determine how much calcium chloride that the plaster core sample contains. If the sample contains more than 2% of calcium chloride, that result can be used to pressure the plaster contractor into admitting that too much was added, and then take responsibility for the plaster discoloration problem. The cost of that is about $100, plus the cost/labor of removing the plaster core.

    The above is why I advocate that pool owners first try to learn and become knowledgeable on this issue and other plaster defect issues that I have written about, and then pursue a remedy with the contractor. And it often works quite well in achieving a favorable outcome for the pool owner.

    I am willing to provide the names of several cement/plaster labs and forensic petrographers that pool owners could send their plaster core samples to.

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