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Cal Poly Plaster Study Conclusions Shown to be Incorrect

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Beginning in 2004, a series of plaster research studies were released by the National Plasterers Council (NPC), which they instigated and financially supported, and which were undertaken by the California Polytechnic State University in San Louis Obispo. In these studies, the researchers concluded that aggressive water conditions were the cause of “spot etching” and other plaster surface defects. The conclusions, and the quality of the research, have long been contested within the industry, yet the studies are still referred to by NPC plaster consultants as authoritative, at times to the detriment of innocent pool owners and service technicians.

In 2015, inorganic chemist Dr. Marcelle Dibrell peer reviewed Phase II of the Cal Poly research. She determined that the conclusions drawn by Cal Poly were not supported by their research, and that they did not prove what the researchers said they proved about plaster spotting.

This year Dr. Stan Pickens, also a prominent chemist and consultant in the swimming pool industry, independently reviewed Phase I of the Cal Poly research. Dr. Pickens was a member of the APSP Recreational Water Quality Committee for two decades, and served as its Chairman from 2014-2016.

Addressing the Phase I report, Dr. Pickens concluded: “While it is apparent that the study was a major undertaking, there are many problems with design study imbalance, flawed sample preparation, failure to control critical variables, and apparent lack of understanding of chemical principles relevant to water balance and sample preparation. These deficits call nearly all of the results and conclusions into question.”

Dr. Pickens also reviewed Dr. Dibrell’s critique of Phase II. In his review he states, “Dibrell’s conclusion that the experiment provided no reasonable explanation for the cause of ’spot etching’ is a reasonable one, since the reported etching did not correlate with the calculated LSI, and since general etching is not the same as spot alteration.” He adds “The occurrence of ‘spot etching’ in pools that – according to the data – were generally either balanced or scaling does call aggressive water into question as a cause. It appears that the Cal Poly researchers were predisposed to find aggressive water as the primary cause of spot etching, regardless of what the data showed.” He also includes the fact that Dr. Dibrell could have pointed out many additional deficiencies in the Cal Poly Phase II report, but notes that “perhaps [she] was too polite to point out the glaring deficiencies in the Cal Poly data.”

Dr. Pickens reviewed another interesting publication.  Apparently at the same time Dr. Kachlakev of Cal Poly was telling the pool industry that they had proven the cause of “spot etching,” he and Dr. Pal (the project’s chemist) and Dr. Rothstein (the project’s petrographer) went to the International Cement Microscopy Association (ICMA) annual conference and presented their material to their petrography peers. But in that setting, they admitted that they did not nail down the cause of “spot alteration.” 

The onBalance group is calling upon the NPC and Cal Poly to retract these invalidated studies in light of Dr. Dibrell’s previous review and these current critiques from Dr. Pickens.

In addition, onBalance is calling upon the NPC to acknowledge that the million-dollar Cal Poly study (and other NPC-associated studies) have not only failed to prove aggressive water is the cause for plaster spotting, but also failed to show that aggressive water chemistry causes gray mottling discoloration, calcium nodules, craze cracking, and spalling/flaking as has been suggested by plaster consultants. They have failed to do so because it simply isn’t true.

Dr. Pickens’ peer reviews may be viewed at www.poolhelp.com/home/onbalance-research/onbalance-research/cal-pol...

Note: This winter, onBalance is constructing their own plaster demonstration pools. They will be investigating parameters including aggressive vs. balanced water chemistry, various levels of calcium chloride set accelerant in pool plaster, and the effects of low-level chlorination vs. regular super-chlorination on organic vs. inorganic color pigments. They assure the industry that this type of testing can be done without the failures found in the Cal Poly process.

 

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Comment by John on December 30, 2017 at 7:35am

Thanks Kim, another great post de bunking myths.

Time and time again I ask question on all aspects of pools and filtration from Peers over here and get daft replies.

This is what Pool Genius Network should be doing IMO.

Lets all work together to sort out issues, I would like to know where turnover rates came from?

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