The National Plasterers Council and onBalance have each issued challenges to the other regarding the cause of spot formation on pool plaster.

The two groups have a long-running feud concerning a number of plaster problems, with the most contentious being spot etching, a phenomenon in which small, often white, spots form on a plaster surface.

The latest round in the decades-long conflict began Sept. 12, when NPC issued a challenge through the trade press, proposing that test pools be plastered and studied to find the cause of the spotting.

NPC officials believe the imperfections mark the beginning of etching deterioration and are caused by aggressive water. OnBalance members say only uniform etching is caused by aggressive chemistry. The spots are different, they say, and don’t involve etching at all. They believe it results from flawed plastering practices, such as faulty troweling, inclusion of certain admixtures and incorrect use of water.

In its challenge, NPC invited onBalance to participate in a study to see if spot etching would occur on pools plastered using the methods proposed by onBalance. Six pools would be tested at venues selected by onBalance. Three would be finished with white plaster; pigments would be utilized on the rest. OnBalance would oversee the plastering and start-up of the pools (to address a disagreement between the groups over the best way to perform start-ups).

NPC would provide parameters for the chemical maintenance to be performed by a member of the Independent Pool & Spa Service Association. The water would be made aggressive to see how the material responds. “We’re going to do real-life water scenarios,” said NPC Board member Alan Smith. “We’re going to be really fair.”

If onBalance is correct, and properly plastered pools are immune to spots, then it should be OK to run the pools with aggressive water, NPC’s logic says.

But OnBalance objected to the study, saying in part that NPC didn’t address the true issue. “The experiment they’re proposing doesn’t even look at the spotting issue — it looks at etching,” said Que Hales, one of the three partners in onBalance, along with Kim Skinner and Doug Latta. “[In onBalance testing] the labs repeatedly say that spotting is not an etching phenomenon. So why would we do test pools that are looking at etching when we already know that it’s not an etching problem?”

OnBalance neither accepted nor rejected NPC’s proposal, but answered with its own, of a completely different nature. In place of the test pools, onBalance seeks to hold a structured discussion in which both organizations would present detailed rebuttals of the other’s studies and research.

OnBalance accused NPC of essentially ignoring studies and research produced by onBalance and the scientists it has commissioned. “The NPC has failed to engage these scientists and prominent cement laboratories on the actual causes of plaster spotting for 15 years,” the proposal reads.

The discussion onBalance proposes would take several months. By Dec. 31, written arguments would be submitted. A few months later, a face-to-face discussion would take place, moderated by a pool and spa professional with a technical background, but who is neither a plasterer nor a service technician.

“Then we can have the debate that has never happened, and address all the facts ... on the table,” onBalance’s proposal states. “If the NPC believes in their position, they will not hesitate to meet this challenge.”

OnBalance wants the discussion to include not just spot etching, but all areas on which the two organizations disagree, including discoloration, calcium nodules, plaster flaking, spalling, severe craze cracking, fading and others.

But NPC National Technical Adviser Greg Garrett said debate has taken place for years in committees, seminars and the trade press. “We’re not interested in any kind of debate,” Garrett said. “What is some point/counterpoint going to do to show the industry who has a more definitive set of concrete theories? You translate theories into real-world scenarios by doing real-world pools.”