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onBalance Gives NPC Conditional YES!

By Marcelle Dibrell 

Last month, the National Plasterer’s Council publicly issued an invitation to onBalance to settle a long, unsettled debate on the causes of a particular type of plaster defect. 

The problem is a kind of light spotted discoloration that appears on newly plastered pools. 

The NPC has spent over 10 years trying to get to the bottom of its cause, conducting extensive research at Cal Poly San Louis Obispo, and has concluded that the spotting is the result of poor water chemistry. 

They explain that cement is composed of five different calcium compounds that are interspersed irregularly throughout the mix, and the weakest of these compounds is calcium hydroxide. 

When water falls into the negative of the Langlier saturation index, it leaches the calcium hydroxide out of the surface, causing whites spots to occur. 

In other words, the white spots occur due to a aggressive water conditions. 

If this is the case, and a service technician has been monitoring the pool’s water chemistry, then surely he is to blame.

The research team onBalance takes exception with this conclusion. 

If the spotting were uniform such a hypothesis would make sense, they argue, but since the spotting occurs irregularly, it seems more likely that the cause lies in the plaster mix itself.  

OnBalance has also conducted extensive research, drilling plaster core samples and sending them to numerous laboratories across the country. They have concluded that the white spots occurs due to a combination of the misuse of a hardening agent, calcium chloride, with hard troweling techniques.

And if that’s the case, only the plasterer can be blamed.

It’s an expensive problem, with two totally different theoretical causes, each of which places blame squarely on two different shoulders. 

Over the years, the two groups have argued the issue via Internet posts and newspaper articles, and the topic has become quite contentious. Fingers have been pointed, insults hurled, and time has healed no wounds. If anything, the enmity has increased. 

So it came as a shock to the pool and spa industry when the National Plasterers Council
issued a formal and detailed invitation to onBalance to join them in science. 

OnBalance is invited to experiment together with the Plasterers on plaster surfaces, subjecting them to conditions designed to avoid and create the spotting.

With bated breath, the pool and spa industry has waited to see what onBalance would do, hoping that they would accept so that we can all move forward. In this issue of Service Industry News, we present their response.

We would like to congratulate Service Industry News for getting the ball rolling toward a resolution to the current impasse between the NPC and onBalance. 

There is a stark divide between the two organizations’ positions, and resolving that divide would be a great accomplishment.

Service Industry News initially proposed a logical, reasonable starting point – to seek common ground by agreeing to a mutual defining of terms through the intermediary of the publication. 

That type of exercise is important in order to make sure that we have a mutual understanding before we try to advance.

However, the NPC invitation now attempts to leapfrog that proposal by jumping to what would be a much later step in the process: further research. 

The biggest preliminary step that will benefit the entire industry is the actual meeting of the minds that we propose. 

Any future testing must absolutely be grounded in what we already know, and what we don’t. So here is our Invitation to the NPC, which is more direct, and will resolve the issues.

The first step is a written exchange of responses to the technical information already out there.

Specifically, we are challenging the NPC to address, in writing, why Dr. Clark of the RJ Lee Group and CTL, Dr. Beyene and Dr. Silsbee of the RJ Lee Group, Niels Thaulow (a leading expert on aggressive attack on concretes), Laura Powers of CTL and Wiss Janney Elstner, and Ron Sturm of River Bend Petrographics were wrong when they said that spotting is the result of poor workmanship and not the result of aggressive water chemistry. 

Not a vague avoidance like in the past, but telling us all exactly where they made a mistake in their advanced scientific methods of petrography, chloride analysis, scanning electron microscopy, backscatter electron imagery, energy dispersive spectroscopy, polarized light microscopy, etc.

In turn, we will do the same — we will provide a specific, written response explaining why any expert analysis from the NPC is factually incorrect, misinterpreted, or misrepresented. 

As an example of a specific argument, we would quote Dr. Kachlekev, Dr. Pal, and Dr. Rothstein (the three principal scientists involved in the foundational phase at Cal Poly / NPIRC) as saying that — 

“While the observations from this study are useful in showing different stages and mechanisms of SA [spot alteration, or spots on the plaster surface] in pools, they do not link SA to a specific set of construction practices or water chemistry conditions.”1. 

This very critical follow-up report and statement was hidden from the swimming pool industry.

This is especially noteworthy because this is the specific study that the NPC claims supports their position that spotting is caused by aggressive attack.

Another example will be specific documentation showing that in Phase 2 of Cal Poly the most spotting occurred in the pools that were balanced, not the pools that were aggressive. Phase 3 and 4 showed that aggressive water did not cause any spotting. We will show that the Cal Poly research actually validates the scientists, not the NPC positions.

The invitation from the NPC, published in the Sept. 15, 2014 issue of Service Industry News, proposed conducting test pools to determine the effect of aggressive water on quality pool plaster. 

Our position is that we have already performed experiments investigating that specific topic many times before. And, so has the NPC. Many of the Cal Poly phases reported on what was designed to be quality plaster in conjunction with aggressive

The NPC expended a huge amount of money at Cal Poly. They assured us that the entire industry was on board.

If that is the case, the entire industry deserves a resolution on what Cal Poly proved and/or didn’t prove.

And the entire industry deserves to know whether our cement scientists were right or wrong in their research.

The NPC has failed to engage scientists and prominent cement laboratories on the actual causes of plaster spotting for 15 years. 

These scientists have examined failed swimming pool plasters and determined that it was improper plaster workmanship that causes spotting. 

These scientists also determined that aggressive water conditions DO NOT cause the problem, which completely contradicts the NPC theory and position.

The next step is the actual debate. 

So our response to the NPC invitation is a qualified yes. 

We are certainly willing to undertake additional future research, but only after a careful discussion and analysis of what is already out there, and then our mutual participation in developing the protocol for any proposed research.

We of onBalance agree that it is time for fact to be separated from fiction and reality from theory on the plaster spotting issue. 

In fact, we fully believe that this has already been done by cement scientists. 

As far as the NPC’s plea to end the debate, our response is that there never has been a debate about the facts.

If the NPC believes in their position, they will not hesitate to meet this challenge. 

Let’s take the opportunity to once and for all, now rather than later, share with the industry what the science says.

Let’s have the debate that so far has never happened, and the industry can know what is fact and reality, not fiction and theory.


1.    Proceedings of the 27th International Conference on Cement Microscopy, 2005, D. Rothstein, D. Kachlakev, and N. Pal pp. 3, 4 (Bold added for clarity. SA is defined as Spot Alteration, or in other words, plaster surface spotting.)


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