The effects of four different chemical startup procedures were studied.
the “Acid” startup – where enough acid was added to lower the pH to 4.5 and alkalinity to zero - about 3 gals. of acid per 10,000 gallons of water
the “pH-Neutral” startup – which equates to about one gallon of acid is added to about 10,000 gallons of water
the “Traditional” startup - where the water is maintained with CSI balanced water; near zero or (0.0) CSI
the "Bicarb" start-up - where the tap water is pre-treated with sodium bicarbonate to raise the TA to 300 ppm and the CSI is about +0.6 to +1.0
Two different methods were used to analyze and determine what chemical startup provided the best protection for a new plaster surface. One method was microscopy (40X magnification) to examine the plaster surface. The other analysis was performed by determining the calcium increase of the water that the plaster coupons were submerged in.
Well made, high quality plaster coupons were formed and placed in water after 24 hours of drying in moderate temperatures. Several coupons were each (separately) placed in water where conditions duplicated the “Bicarb” startup. The second set of coupons were placed in typical balanced water (simulating a “Traditional” startup), the third set were placed in moderately aggressive water (an SI of –0.8, similar to the so-called “pH Neutral” startup), and the fourth set were placed in water that simulated an “Acid” startup (which equals a very aggressive –4.0 SI).
After three days, the coupons were removed and the calcium level in each water tank was tested. The Bicarb startup water had a zero to 2 ppm increase in calcium, the Traditional start water had an average calcium increase of 7 to 10 ppm, the pH Neutral (moderately aggressive) startup water had a 15 to 20 ppm calcium average increase, and the Acid (or zero alkalinity) startup process had an average calcium increase of 60 to 80 ppm. When the Acid startup process was extended for an additional four days, the results indicated a calcium loss of about 120 ppm! This is significant because an increase in calcium (in the water) indicates a loss of calcium from the plaster, and increased porosity of the surface. As can be seen from these results, the bicarb startup program had the least amount of calcium loss, preserving the high surface density which provides the best protection for the plaster surface.
When 40X magnification was used to examine the plaster surface, we found that the Acid startup coupons were slightly etched, with the thin layer of cream (cement) missing, the aggregate exposed, and the surface uniformly rough. On other hand, the Bicarb startup coupons were very smooth, with the cement cream layer still intact and the aggregate not exposed. The other two methods fell in between the Acid and Bicarb results, with the Traditional startup coupons showing just a slight effect of exposed aggregate, and the pH Neutral startup coupons just a little more exposed than the Traditional. This microscopic examination was consistent with, and confirmed the results found by using the “calcium increase” analysis method.
As can be seen, the results obtained by this study shows that the Acid startup is the most detrimental method and causes irreparable harm to a new plaster surface. While the Acid startup may dissolve plaster dust and help the surface look good for a few months, it should be understood that this etched and more porous plaster surface will deteriorate and stain earlier and easier. The Bicarb method, on the other hand, is an improvement on the industry standard Traditional method.
For instructions on Bicarb Start-up, see this post: a-bicarb-start-up-guide-for-tfp-members-t57316.html
Also see this post: aggressive-water-versus-improper-pool-plastering-t51900.html
For proper plastering practices, see this post: ten-guidelines-for-quality-pool-plaster-t42957.html