A Response to Our Fading Plaster Story

Editor's note: To the frustration of pool builders and homeowners alike, colored pool plaster sometimes loses its saturated hue. Some say water chemistry is to blame, but in the August 2014 issue, Que Hales suggested it might be the composition of the plaster that causes the issue. (Click here to read the story.) Check out this response from the National Plasterer’s Council:

The article written by Que Hales from OnBalance, “Until the Colors Fade,” was most informative. There are insightful and accurate observations made in this article. However, there are a few inaccuracies and/or misconceptions leading to conclusions that we believe do not fully allow the reader the ability to consider the entire issue surrounding pigment “fade.” 

First, we need to clarify one point. The colorants used for swimming pool plastering are not “dyes.” They are “pigments.” Although this may have been an oversight by Mr. Hales, it is a very important distinction. We make this point because dyes are not used by the swimming pool industry to color cementitious interior finishes. As correctly stated by Mr. Hales, pigments (not dyes) can be further identified as either organic pigments or inorganic pigments. Traditionally, it is thought that organic pigment does not last as long as inorganic pigments. There are many reasons for this thinking, and there are those in the industry who feel that there are exceptions to this, but we will not be addressing this. However, we would like to address several other issues Mr. Hales raises in is article. 

Calcium chloride DOES NOT cause pigment fade. 

In fact, as the calcium chloride content increases within a given mix design, most pigments tend to slightly darken, or “shade.” Most pigments available to the industry are compatible with calcium chloride. Meaning, there is typically no adverse reaction that takes place early on between the calcium chloride additive and the pigments. The calcium chloride immediately ionizes during the mixing process and reacts with the cement. However, since calcium chloride is known to slightly intensify the coloration, we suggest that samples or coupons having similar calcium chloride content be shown to the builder or owner prior to application whenever the variance of coloration is expected to be significant. Generally speaking, this is seldom an issue. Again, the decision to allow the usage of calcium chloride for swimming pool plastering is not related to an “incompatibility” issue, but rather to the potential for a slight variation of increased color intensity (shading) that may be noticed. And, most certainly, is not the cause of pigment ‘fade’.      

Chemical attack does not always show as surface etching.

According to Mr. Hales, etching should be visible on the surface if aggressive chemistry played a role. This is not true. Leaching deterioration is an example of an attack that does not typically show visible signs on the surface until long after substantial deterioration has already progressed within the material. And leaching deterioration is generally found to have played a role in most pigment ‘fade’ issues.        

Proper laboratory testing is fundamental to arriving at valid conclusions. 

According to this article, the investigative work undertaken by Que Hales and many of his conclusions consisted primarily of: 

  1. Visual observation in the field that showed a lack of etching at the surface of the material;
  2. the chemical maintenance logs of the service technician; and,
  3. the chloride content of the finish material.

Unfortunately, the above three are simply indicators that may be useful in helping to facilitate the actual in-depth testing necessary to make proper conclusions. There are longstanding specifications, standards, manuals, and guides that detail the proper procedures and investigative methodologies that must be undertaken in the laboratory in order to properly identify the actual condition, deterioration mechanism(s),or failure of a cementitious material. Therefore, the above three investigative work steps are simply not sufficient to support many of the conclusions that Mr. Hales makes.

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