The group onBalance plans to build test pools to study the relationship between plaster discoloration and defects and techniques for applying the materials.

The outspoken consulting group strongly opposes the notion that poorly balanced pool and spa water can cause the phenomenon that some call spot etching. Instead, its members blame plastering techniques, especially the addition of calcium chloride to the mix, and the use of water while troweling. This has caused vocal and sometimes very public disagreements with the National Plasterers Council, which draws a connection between water chemistry and spot etching and has performed is own testing.

OnBalance plans to locate the test pools in Tucson, Ariz., on grounds belonging to member Kim Skinner’s company. Testing methods are being developed and will be released for public comment in April or sometime after, Skinner said. A group comprised of onBalance members and associates will review the comments.

Some details are known at this point, Skinner said: Two small pools will be finished by two unnamed plasterers, one of whom is an NPC member. These professionals are expected to contribute to testing protocol. The plaster application will be videotaped, with footage made available to the industry, Skinner said. The group will finish one pool in white plaster, with sections that have different amounts of calcium chloride to test proportions. The other vessel will be finished with colored plaster, with sections finished in various types of pigments. Both aggressive and balanced water will be included in the testing.

Use of water during troweling will be minimal, Skinner said. “We will not wet trowel, or if we do, it will be very minimal — it will just be for lubrication only,” he said.

He said the group is not in a rush, and expects that the pools will be plastered and filled as late as autumn. “We just want to make sure it’s done right,” Skinner said.

OnBalance will monitor the vessels for 10 to 12 months, taking chemical readings daily and inspecting the pools monthly. “We’re going to have very close monitoring of the water chemistry, and it will all be made available to the industry free of charge,” he said.

“We feel this is one way to add more information, so people who are on the fence or not sure what to think and what causes the issues, this will give them further information with which to conclude what causes these plaster problems.”

The group currently is raising funds for the study.

This is a late-breaking story. Look for follow-up coverage, reactions and analysis in future issues and at

Correction: A previous version of this article misstated onBalance's beliefs regarding the connection between water chemistry and plaster issues.