Last week, Pool & Spa News covered a challenge that the National Plasterers Council issued to the consulting and research organization onBalance, in the name of resolving a longstanding disagreement over what causes the phenomenon commonly known as "spot etching."

With both citing research and studies, NPC believes the condition is caused by aggressive water chemistry, while onBalance says it results from improper plaster application.

In its challenge, the plasterers organization proposed performing tests on six pools, either in real-life settings or at the National Pool Industry Research Center at California Polytechnic State University, San Luis Obispo. OnBalance would choose the pools and oversee plastering and start-up, while NPC would establish the parameters for chemical maintenance, to be performed by a service tech who belongs to the International Pool Service Industry Association. The water would purposely be made chemically aggressive.

The basic idea says that if the plastering practices onBalance proposes are enough to inhibit the formation of the white spots, then aggressive water should not result in the spotting (as opposed to uniform etching throughout a pool, which OnBalance does attribute to aggressive chemistry).

This week, onBalance issued a response, which neither accepts or outright rejects the challenge, but instead laid out a completely different proposal. 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 accuses the NPC of essentially ignoring the studies and research produced by onBalance and the scientists it commissions to analyze core samples.

“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 place over several months and include written arguments as well as face-to-face discussion. By Dec. 31, both organizations would produce rebuttals to the other’s science and send it to each other and the trade press. A few months later, a face-to-face discussion would take place, moderated by a pool and spa professional with enough technical background to follow the conversation, 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 that are on the table,” onBalance’s proposal says. “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.

Read NPC's challenge in full:


Read onBalance's complete response: