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Attention NPC! New invite from onBalance

Sixteen years ago what was once a cooperative relationship between the National Plasterers Council and onBalance disintegrated — over the spotted plaster debate. The NPC maintained that “spot etching” (as they call it) is caused by aggressive water chemistry, and onBalance maintained that plaster “soft spots” (as we, in turn, name it) is caused by improper plastering technique. It has been an uncomfortable argument ever since.

We propose an experiment involving the NPC, onBalance, IPSSA, UPA, Service
Industry News, and any other interested industry organizations. We propose that these organizations approach new, existing pools that have already suffered spotting or gray mottling discoloration. The pools would then be drained, cored, and the core samples sent to multiple cement labs to determine the cause and effect of both problems.

Each organization could pick a laboratory of their choosing. It is our expectation that with sufficient data, laboratories would come up with conclusions about the phenomena. All of the various independent reports should then be peer-reviewed by a single, top-credentialed petrography expert. The final review would be presented to both the pool industry and also presented and published by the petrography industry at its annual conference and proceedings.
Let’s get the experts started, so we can get this settled — and all sit comfortably together around the table again.


OnBalance’s proposal comes in response to a recent solicitation from the National Plasterer’s Council for new research ideas. This January, the council sent out a survey asking its members for new research ideas. Among those ideas, they NPC suggested doing future research on causes and solutions of spot etching and gray discoloration.

As a publication dedicated to pool service professionals, the staff of Service Industry News thinks it’s a great idea to finally resolve the causes and solutions of plaster defects. In addition to being unfair to customers, the lack of resolution has pitted industry members against one another; plasterers against service techs, and the problem has gone on too long.

NPC’s executive director, Jeff Henderson, has said, “We need to get out of the drawing room, and get away from the lecterns and the microphones and get back in front of cement holes in the ground.”

For the NPC, that typically means building test pools of a variety of materials and subjecting them to a variety of water conditions. For onBalance, that means drilling core samples from existing, deteriorated pools and sending them out for forensic analysis.

OnBalance’s proposal is an idea that could be the first step to resolving a decade’s long conflict. Depending on what is learned, the experiment could be useful in designing new test-pool studies.  Some may recall that NPC-sponsored scientists have already conducted research on spot etching and surface discoloration.

Throughout at least five years of study these scientists continued to report that aggressive water chemistry is the single most important factor leading to spot etching and surface deterioration. In their final analysis, they determined that sometimes even proper water balance cannot completely prevent it.

This research was carried out from 2004 to 2007 at the National Pool Industry Research Center (NPIRC) located at California Polytechnic State University, San Luis Obispo, and published in four separate reports. As each report was made public, onBalance took issue with the conclusions, pointing out that the data does not support the conclusions. onBalance implored the NPC research team to account for inconsistencies in their reports but were rebuffed.

Some in the industry know that onBalance has also done research on the subject, sending core samples of spot- altered pools to independent laboratories for petrographic forensic analysis.
Petrographers are the forensic specialists in the cement-based materials industry. They utilize equipment ranging from scanning electron microscopes to X-ray diffraction and more.

They identify cement pastes, aggregates and admixtures at the constituent level, and determine what went wrong with failed materials, from dams and piers to bridges and buildings, freeways and atomic power plant cooling containments. With the help of these scientists, onBalance has concluded that spot alteration and gray discoloration is the result of poor plaster workmanship.
Specifically, the addition of excessive calcium chloride, adding water to the hardened plaster surface causes soft spots, and late troweling causes gray discoloration in the plaster.

In September 2014, the NPC shocked the industry when it challenged onBalance to settle the debate once and for all. They invited onBalance to come and show them the plastering techniques that will eliminate spot etching. OnBalance could provide their own crews to plaster six pools, using methods of their choice to prevent spot alteration. Meanwhile the NPC would ensure aggressive water chemistry to try to promote spot etching.

OnBalance responded to the challenge with a conditional yes. They agreed to future research…but only after both parties have an honest discussion about the research that has already been done.

NPC member Alan Smith said, “They keep it at the level of an esoteric argument. If they know how to do it, why won’t they show the industry what they are talking about?”

However, according to onBalance,  this sort of comment is an attempt to avoid discussion of the many lab reports that are already available. Furthermore, “the vast majority of pools do not spot and plasterers do know how to plaster pools properly. They don’t need to be taught by us,” onBalance said. 

Thus the project was dropped.   OnBalance’s proposal re-opens the conversation, but does so in a non-esoteric manner that the NPC may find more acceptable. So onBalance says, “game on, and let’s start with the science first!”

To date, dozens of petrography reports have been undertaken on both sides of the aisle.
Why not take advantage of that now with this new proposal.  Both the NPC and onBalance believe that scientific evidence is the key to determining the cause of plaster defects.
Could onBalance’s proposal be the first step?

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