Translate to:

How White Pool Plaster Can Turn Gray

  • Rating: No Rating

One would think that when mixing white cement with white limestone aggregate, the final pool plaster product would always be white. But that is not always the case.

Unfortunately, white pool plaster sometimes turns gray (or grey) either immediately or a few months after the pool is filled with water. So what causes that to happen?

The concrete/cement industry has documented that late hard troweling can cause a cement surface to darken, mottle, and spot. Also, adding a high dosage of calcium chloride (CC) to a plaster mix causes a slight darkened (graying) hue to develop. The combination of the two issues is really problematic. The pictures below of plaster coupons demonstrate how white pool plaster can darken and mottle. 

Picture above: Top left coupon: no CC added, properly troweled. Top right coupon: no CC added, late hard troweled. Bottom left coupon: 2% CC added, properly troweled. Bottom right coupon: 2% CC added, late hard troweled. All were placed in balanced water for one year.

Note the darker color of bottom left coupon that had 2% CC added in comparison to top left coupon which had no CC added.  Note the darker color of bottom right coupon that had 2% CC added and received only minimal late hard troweling in comparison to the top right coupon, which had no CC added, and received four times the amount of late hard troweling.


Picture above: Note that the top coupon is the whitest. That coupon had zero CC added and was properly troweled. The middle coupon had 2% CC added, received some late hard troweling. The bottom coupon had 2% CC added, received some late hard troweling, and placed in balanced water for one year. Note how the bottom coupon darkened even more after being submerged in water.

Pool owners pay good money for uniform white plaster, not gray, blotchy, or discolored plaster.

Views: 461


You need to be a member of Pool Genius Network to add comments!

Join Pool Genius Network

Sign in


 or Sign Up
By signing in, you agree to the amended Terms of Service and Privacy Policy.
Forgotten your password?


Latest Activity

Timothy M Kersting is now a member of Pool Genius Network
John McGehee joined Brian Galella's group
John McGehee joined Richard A. Falk's group

Water Chemistry

This group is for in-depth discussion of pool and spa water chemistry issues at a more technical…See More
Kim Skinner posted blog posts
Jan 17
Kim Skinner replied to John McGehee's discussion Issues with using rainwater for everything pool construction and maintenance related
"Using rain water for mixing with cementitious materials is fine.  I don't see significant…"
Jan 17
Kim Skinner's blog post was featured

The LSI is Reliable

Using the Langelier Saturation Index as a guide for maintaining proper pool water balance and to…See More
Jan 16
Jackie gingras is now a member of Pool Genius Network
Jan 15
Profile IconShaunta Clint and Marquise Pools, LLC joined Pool Genius Network
Jan 10

© 2019   Created by PGN Admin.   Powered by Pool Genius Network

Badges  |  Report an Issue  |  Terms of Service


Live Video