Posted by Kim Skinner on August 18, 2009 at 12:35pm
For one through seven, see "Making Durable Pool Plaster #1"Eighth, once the pool has been plastered and is finished, the filling of the pool with water should not be started too early. Conditions vary, but as a general rule the water should not be turned on for at least 6 hours after finish troweling. This allows the plaster to properly harden before being submerged in water. Even balanced tap water can dissolve certain plaster components from an insufficiently hardened plaster surface, creating increased porosity and early deterioration. onBalance conducted a research study that documented this fact.Ninth, steps should be taken to ensure that the fill water is appropriate for filling a new plaster pool. Studies have shown that 75% of the damage done by aggressive water to new plaster surfaces occurs within the first 24 hours, although this deterioration is uniform. Other new plaster surface discolorations such as drips, splotches, spotting, trowel marks, hand and footmarks, etc. are caused by finishing errors. Surfaces can be further damaged by using aggressive (acid) start-up techniques, which can increase the amount of uniform surface loss. Baking soda startups, for example, will both neutralize aggressive fill water and also promote a superior plaster surface.Tenth, once a pool is filled, balance the water and keep it that way. Although this does not “create” long lasting, durable plaster as the above practices do, balanced water chemistry helps preserve that surface. Long experience has shown that aggressive water uniformly etches plaster, and over-saturated water scales it. The Saturation Index is a good guide – water should have a saturation index value in the range of –0.3 to +0.5. This range does not actively promote either scaling or etching.White plaster is a good and relatively inexpensive surface that many pool owners desire. Although pozzolans, blended cements, quartz and pebble aggregates, can provide even better results, they do not negate the need for proper workmanship, and the last century has shown that most standard white plaster lasts about 20 years with reasonably good maintenance. It is not inherently weak, and unable to stand up to the “real world” pool environment, including the vagaries of chemistry and maintenance. This is evidence that many pools are plastered correctly by good plasterers.Now, in the real world we all realize that some variables will be outside the control of even the most professional tradesman. Weather happens, materials that are assumed constant may vary, good-intentioned but unknowledgeable outsiders intervene, etc. We also understand that pool plaster is a hand-crafted product, and nothing in nature – especially where humans are involved – is perfect.However, a plaster finish can also be made poorly. If only one minor abuse of the above guidelines is performed, then it probably won’t manifest itself with any visible adverse effect early on. If more than one of the above mentioned practices is significantly abused, then a far quicker deterioration can take place even in balanced water. The greater amount of “plaster dust” a new plaster pool creates is an indication that some improper practices occurred. Virtually no plaster dust in new plaster pools would occur if all of the above proper practices and workmanship issues were followed correctly.Unfortunately, during the early stages of the plaster’s age, many problems that have commonly been attributed to improper water chemistry may actually be due to one or more of the above workmanship issues.As a result of our investigations, when plaster begins to show signs of discoloration or deterioration within a few months, and the water balance has been maintained in a reasonably balanced range, we suggest that those involved should investigate whether the above guidelines for providing and making quality and durable plaster were followed. Today’s technology provides the ability to analyze plaster for most of the above-mentioned issues, such as water/cement ratios, cement/aggregate ratios, calcium chloride contents, whether the surface is more porous than the interior matrix due to water additions, and whether the plaster has been etched by aggressive water or has simply deteriorated due to being of poor quality.Adhering to good plastering practices, standards, and workmanship, and then following accepted water balance practices will eliminate most all pool plaster problems, pool owners will be happy, and our industry will prosper.Provided by onBalance, a consulting group comprised of Que Hales, Doug Latta and Kim Skinner
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