Cal Poly Pool Plaster Conclusions Shown to be Wrong… Again!

Data and Conclusions Often Even Directly Contradict Each Other…


Beginning in 2004, a series of swimming pool 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. (Unfortunately, we can’t provide links to the study reports because the National Plasterers Council controlled access to the material by charging $500 per copy.) 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, 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 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. He is also active in the Model Aquatic Health Code (MAHC) process.

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.”

After reviewing Cal Poly Phase I and Dr. Dibrell’s critique of Cal Poly Phase II, we had Dr. Pickens take a look at another interesting publication. Apparently at the same time Dr. Kachlakev of Cal Poly was telling the pool industry that they had nailed down “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 “spot alteration.”

onBalance is calling on the NPC and Cal Poly to retract these invalidated studies in light of the reviews by Dr. Dibrell and Dr. Pickens.

In addition, onBalance expects 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.