Plaster Installation and Maintenance - Further Reading

Plaster Installation

To find colors of different plaster finishes look at the Pool Finish and Color Viewing Room.

In most cases the Pool Builder or "contractor" who you are hiring does not have the plaster crew working for him. He subcontracts the plaster work to a specialty contractor. So all your talk to your "contractor" about the quality work you want done is rarely passed to the actual crew who will do the work. There is no substitute for being on site when the plastering is done and watching closely that they follow the best practices described in our articles. Plastering is a custom manual process where decisions made on the job site affect the quality fo the work you get.

Get educated and get involved in watching over your project. Trusting a contractor and just writing checks is rolling the dice on getting a quality plaster job.

To get an idea of the pool plastering process you can read the EXPOSED AGGREGATE POOL FINISH GUIDE from SGM the makers of Diamond Brite plaster.

Pool Plaster Tips for the Average Homeowner is a good place to begin reading about how to get quality plaster installation.

Ten Guidelines for Quality Pool Plaster There are proper steps to follow for the making of durable pool plaster. There are also improper practices that can lead to early deterioration, discoloration or other failures. Above is a ten-point checklist that will help achieve a lasting and discoloration-free plaster.

A Plastering 'Watch List' Taking control of the plastering process is within reach of any quality-oriented designer or builder, declares Kim Skinner. To help you on your way, he offers this step-by-step guide to managing what should happen on site before, during and after plaster application takes place.

Not All Color Pigments are Good for Pools It appears the plaster products that contain “organic” pigments become bleached (loss of color) over time when subjected to chlorine (an oxidizer). But products with “inorganic” pigments generally do not become bleached. Additionally, experiments which subjected both organic and inorganic pigments to LSI aggressive water showed that neither type of pigment lost their color from etching.

The Art of Good Pool Plaster Color An attractive plaster color (other than white) is often preferred by pool owners. However, it is very difficult for plasterers to produce a uniform and consistent color. The reality is that there will always be some minor shading (mottling) and variation in the color and can never be uniform looking like paint or fiberglass.

Why Acid Wash New Quartz Pool Finishes? It is understood that muriatic acid can dissolve and etch a plaster surface. Therefore, why, after a plastering finisher works hard to achieve a smooth, hard, brand-new, hand-crafted, quartz pool-finish, would anyone immediately perform an “acid wash or acid bath” on that pool and that plaster? Yes, doing so can increase the exposure of the quartz color; but isn’t that removing some plaster material and shortening the life of the plaster and leading to future problems?

New plaster on renovated pool- when to refill? Cement products need a certain amount of time to harden before being submerged in water, because it is very easy to dissolve the surface of fresh unhardened or uncured cement/plaster. I don’t see how anyone can disagree with that. In fact, the NPC's own plaster tests (Cal Poly-NPIRC) provided evidence and results of that fact. Therefore, shouldn’t homeowners try to request waiting a few hours before starting the water and reaching an agreement regarding the warranty?

The key is to wait at least 6 hours before starting to fill the pool, and then fill as rapidly as possible AFTER waiting 6 or more hours (but wait no longer than 24 hours). Submerging plaster in water before it has a chance to sufficiently harden is a mistake. Builders should know that, but some don't. It is a fact that some of the plaster surface dissolves into the fill water when it hasn't hardened sufficiently making a more porous surface. That results in a poor start for the plaster product to last more than 20 years.

The fill water itself should be balanced (actually having a slightly positive CSI) rather than being soft or aggressive according to the CSI.

Start-up Chemistry for Plaster Pools 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

Pool Plaster Start-up Alternative Orenda Technologies has recently unveiled a new start-up program that is somewhat similar to the onBalance Bicarb start-up process. Instead of adding sodium bicarbonate, Orenda suggests adding calcium (calcium chloride) to low calcium tap water while filling brand-new plaster pools, which also like the Bicarb start-up, prevents the formation of plaster dust. We at onBalance have received numerous communications asking us if this calcium program is compatible with, or a viable alternative to the Bicarbonate Start-up Method that also prevents plaster dust. The answer is yes.

When Should Salt be Added? In our industry, there seems to be some consensus to wait 30 days before adding salt to new plaster pools, yet some say it is okay to add salt within a couple of days of filling the pool. Who is right? This thread describes why it appears that the recommendation to wait 30 days before adding any salt is appropriate for most plaster pools, including quartz and pebble pools.

Why no heater use for first 30 days? With new plaster there is a lot of plaster dust in the water and the pH is usually very high. When you heat water the potential for scale formation in the heater increases significantly. The actual timeframe for waiting to use the heater has no real merit. As long as the plaster dust is under control and the pH is in range there is no reason not to use it. Your risk of rushing to use the heater is scale clogging up the heater coil.

Why no wheeled cleaner for first 30 days? Plaster is sufficiently hard once the pool is full of water. Pool cleaners can be installed and utilized after about two days if there is no plaster dust forming. The reason that tracks develop is usually from plaster dust being "packed down" by the pool cleaner wheels and then not removed by brushing. So it can look like an "indention" (and discolored) but it is not an indention. Brushing afterwards can help prevent the plaster dust from sticking on the plaster.

Installation Tips

• Full chipouts should be done with one of the following methods:
  • If chisels are used then it should be flat chisels, not pointed chisels. Pointed chisels remove too much gunite and can weaken the shell
  • High pressure sand blasting is superior to chiseling to remove plaster
  • Hydro jetting using high pressure water is also effective at removing plaster Read PSN:Water Jetting

• Sandblasting, chipping out, hydro jetting is usually done based on the specific job and the equipment of the contractor. Very few contractors have the equipment to sandblast, and even fewer have the equipment to hydro jet. This has led to the chip out becoming the default method for large parts of the country.

• A full chip out does not generally need or require a bond coat to be applied. However, there is no harm in doing so, and in fact, may improve the bonding of the new plaster coat. Bond coats drastically prevent delamination on new or remodeled pools. There may be bond coat products that aren't as good as others. But for the most part, bond coats generally help and improve bonding, but are not necessary with a full chip out. So I like the contractor that recommends a bond coat.

• Most bond coats are also waterproofing agents and are flexible enough to allow for decoupling of the plaster from the shell. Something that is not widely known or discussed is that plaster has a significantly higher compressive strength (8-9,000 PSI) compared to the shell (3-5,000 PSI) and because of this the two materials can have slightly different expansion characteristics which can be problematic in certain situations. BaseCrete is probably one of the the best bond coat products to use although there are several other materials that are worthy options.

• Take a sample from every batch of the plaster while it is being applied. Use plastic cups and write on the cup the date, time, address, and batch number. If there is a problem later, you can send the sample to the lab without having to take a core out of the pool.

• The normal CSI guidelines are not applicable to new plaster finishes under 30 days old. It is actually necessary, to achieve a smooth and dense surface, to have about a +0.5 CSI during the first 30 days. This is because the plaster (cement paste) surface contains about 20% calcium hydroxide, which is somewhat soluble in balanced and slightly positive CSI water and can be dissolved away. The plaster surface needs to be "carbonated" before the CSI should be lowered to the acceptable and balanced range. And that generally is achieved during the first month under balanced water.

• Pool owners can discuss these guidelines with their Builder or plastering sub-contractor and let them know that you understand some of these issues. When asking for bids, you can ask if they will follow the above guidelines. Some of them already do. The one that agrees should be the one you hire. You can watch them, make notes, film them, and even pay a little extra for them to slow down by not adding a high content of calcium chloride and adding water while troweling. It would well be worth the price. And one important thing I forgot to include in the above post, is to suggest to the pool owner to take two paper cups and scoop in two different plaster samples of a recently mixed and fresh plaster material (before it is applied to the pool and hardens) and keep for future analysis if something goes wrong.

• Pool owners can influence pool plasterers by simply telling them to not add more than 1 lb. of calcium chloride to 100 lbs. of cement, and telling them to not use excessive amounts of water while troweling towards to end of finishing. (They could sign a letter of statement for you). If plasterers time the troweling correctly and have enough personnel, they only need to lubriate their trowel slightly with some water, and perform the final troweling.

• On very hot and dry (non-humid) days, plasterers should place a tent or sun screen over the pool to slow down the hardening process, so that they don't need extra water to re-work the plaster.

• Tell your plasterer to make the plaster mix thick like oatmeal, and not soupy. Then take some pictures during the plastering process, then the plasterer will hopefully be extra careful to do the job correctly.

• It is understandable that pool builders want to make sure the color quartz shows up vividly. Unfortunately, they think that an acid wash is the only way to achieve that, and that an acid treatment does that quickly and easily, and cheaper. However, there is a way to expose the quartz sufficiently by simply using good troweling techniques. Why Acid Wash New Quartz Pool Finishes? explains how to easily do that. Another way to expose the quartz color is by power sanding, but as mentioned above, it is time-consuming and more expensive. (Let's understand that power sanding is not for pebble finishes.) Hydrazzo finishes (which is also a quartz finish) specifically perform power sanding of their product. All quartz finishes could use that sanding program. That would cause less damage to the plaster surface. Lastly, after a quartz plaster finish (and pebble) has been exposed by any method, a Bicarb startup can and should be used.

Addition of Abalone Shells to Plaster

Abalone shells have, in the past, caused problems with plaster discoloration, specifically brown rings forming around the shell chips. The culprit seems to be non-pool grade shells being used that were not properly processed to remove all of the organics in them. These organics then slowly leach out into the plaster, react with chlorine in the pool water and form a brown ring. Nothing can remove the stain and the fix is often to simply chip-out and redo the plaster.

Discuss with the plaster applicator WHERE they are sourcing the abalone shells from. Abalone shells from a reputable plaster company and properly processed and rated for pool use should be able to be used. If the applicator can't GUARANTEE that the abalone is a pool grade material, then I would not use it.

While abalone can add a nice glittery appearance, I think the downside risks are not worth it.

Abalone, like all sea bivalves, creates it's hard shell from calcium carbonate and other minerals through biological processes. They are beautifully complex in that they use enzymes and proteins in the biological process to structure nano-scale (one-billionth of meter) material layers. Scientists and engineers would love to be able to recreate in the lab what nature has so beautifully constructed but, to date, the best humans can do is a very sad and simplistic process.

All that is to say that these creatures leave organic residues behind in their shells from the process of building them. It has been shown that abalone shells in white and light colored plasters can eventually cause brown staining (little brown halos) over time as the proteins and organics leach out into the surrounding plaster matrix. Chlorine and acid washing are not effective in fixing this.

Remember that abalone is a natural product that is derived from the shells of sea mollusks. They can and will contain organic compounds. If they are not processed and washed properly, problems can arise years later when you no longer have the PB on the hook with your money. These stains appear to be permanent and, in most cases, the plaster has had to be redone.

We have had members report brown stains in their pool from the organics in abalone decomposing. See Abalone Shell Chips Causing Brown Stains in Diamond Brite Plaster and I have a plaster problem.

Plaster Start-Up Guides

See Plaster Start-Up Guides

THE BEST PLASTER POOL START UP How a startup program deals with and prevents the detrimental process of “plaster dust” forming in newly plaster pools is the key in helping to preserve a quality plaster finish that will last 20+ years.

Plaster Maintenance

Calcium increases of the pool water can occur for at least 5 different reasons:

• aggressive water (low CSI) - aggressive water that has a negative CSI of around -0.8 would dissolve and remove calcium from the plaster finish and raise the calcium level of the water by about 50 ppm over six months time.
• bad plaster mixing and application - Calcium will naturally bleed out of poorly mixed plaster that also has a high amount of calcium chloride added to the plaster mix.
• adding tap water that replaces evaporated water
• adding calcium hypochlorite (powdered chlorine shock)
• adding calcium chloride to the water to intentionally raise the calcium level.

The CSI is Reliable for Plaster-based Pools Using the Calcium Saturation Index (also known as the LSI in the pool industry) as a guide for maintaining proper pool water balance and to protect pool plaster, including quartz and pebble finishes, has become a mainstay in our industry for good reason.

All Plaster Finishes Should Last 20 Years All pool plaster finishes should last 20 years or more. However, some last only 5 to 7 years, and some less than a year before the plaster surface deteriorates, discolors, and looks terrible. Why the difference? Very often, plaster quality. Studies on pool plaster and cement/concrete flatwork have shown that poor workmanship practices have the greatest effect on durability, deterioration and discolorations. Various studies also confirm that water chemistry plays only a minor role.

Pool Water Balance is Not (Always) the Problem The Bottom Line - Maintaining slightly aggressive water (LSI or CSI of -0.1 to -0.5) is acceptable. It does not cause rapid plaster deterioration and discolorations problems on quality applied pool plaster. The plaster problems mentioned in the thread are prevented by following good workmanship standards. Right now, there are none.

Reducing High Calcium Levels in Pools By manipulating the water’s saturation chemistry, calcium can be removed via an ion exchange-style process of adding sodium to remove calcium, and then clear the water by filtration.

High CYA Levels Do Not Stain Plaster Contrary to some misinformation that has lately been floating around in the pool industry, high cyanuric acid (stabilizer) levels do not cause gray discoloration, or white spotting (“spot etching” as some incorrectly call it) in plaster swimming pools, no matter what. And there are several studies that have documented that.

The Zero Alkalinity Acid Treatment The concept of the “Zero Alkalinity” process (also known as a No drain Acid Wash) is to make pool water aggressive enough (by adding acid) to dissolve and remove stains or scale from cement-based plaster surfaces, including quartz and pebble swimming pools. Unfortunately, this process may remove some of the plaster surface material.

Plaster Problems

Being Blamed for Plaster Discolorations? Don't Get Hoodwinked Some newly plastered pools (including quartz and pebble finishes) may develop either white soft spotting (also called "spot etching" by some plasterers), streaking, calcium nodules, gray mottling discoloration, spalling (flaking), or severe craze (check) cracking within a few months after being plastered, and whoever has been maintaining the water is often incorrectly blamed for those plaster problems and defects.

Diagnosing Pool Plaster Problems

White Spotting of New Plaster Pools The problem of plaster spotting has been an ongoing puzzle and controversy in the swimming pool industry for over three decades. The generally round, smooth-yet-unsightly white soft spots in new plaster pools have long been a source of contention among pool plasterers, and pool chemical service firms or pool owners, each blaming the other for the phenomenon.

Not All Color Pigments are Good for Pools Plaster products that contain “organic” pigments become bleached (loss of color) over time when subjected to chlorine (an oxidizer). But products with “inorganic” pigments generally do not become bleached.

Scientific Evidence on Plaster Spotting provides pictures and scientific evidence from the cement petrographers who performed “failure analysis” examinations on white spotted pool plaster cores.

How White Pool Plaster Turns Blotchy This experiment below explains how white pool plaster can become blotchy gray, and also have white areas mixed into the gray areas.

How White Pool Plaster Can Turn Gray 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?

Calcium Nodules in pools What are calcium nodules? In swimming pools and spas, they are small mounds, bumps, deposits, or “slag” piles of calcium carbonate which are formed from material that has been released from the plaster. The small calcium nodules are rough to the touch, hard, and generally gritty. Nodules may form singularly (far apart or sporadically), or many and close together along a crack in the plaster surface.

Unusual Calcium Nodules About a dozen years ago, the onBalance team began investigating a slightly different and smaller type of nodule in recently plastered pools. Some of the nodules had not developed on delamination cracks, but instead, they had formed on severe “crazing” or “check” cracks that were nearly invisible. See photos of small nodules

Pool Plaster "Spalling" One of the arts or skills of the pool plastering trade is properly timing the troweling process. If troweling is performed when water is present on the surface of the plaster, forcing water back into the plaster paste causes excessively high water:cement ratios in the surface finish, weakening it.

Why Are Calcium Crystals Forming in Pools? In recent years, calcium crystals have been forming during the winter at a higher rate in some newly plastered swimming pools. From the reports we have heard, this problem seems to occur more often in the northeast of the country. Apparently, pool builders, plasterers, and service techs involved have not been able to determine the cause of these sharp and abrasive crystals and how to prevent them from forming on new plaster surfaces, including quartz and pebble.

Plaster Spalling One of the arts or skills of the pool plastering trade is properly timing the troweling process. If troweling is performed when water is present on the surface of the plaster, forcing water back into the plaster paste causes excessively high water:cement ratios in the surface finish, weakening it. Sometimes the surface dries too fast. If the surface becomes too dry, with a dry “crust” on the surface but a wet paste underneath, a weakened zone can be formed just subsurface. This can happen when plastering on dry hot days, during low humidity, in wind, etc. It can also include too much drying between trowel passes, excessively late hard troweling, and overworking (over-troweling) the finish. If this happens, the top of the finished plaster will look fine. However, after time this weakness is manifest by a thin 16th to 8th inch thick layer of the surface flaking off, generally in small areas or spots. Often, these weak areas do not flake off until the pool is drained of its water and the plaster dries out.

Plaster Polishing

There are times when polishing plaster is the best way to fix roughness or scale and is often preferable to an acid wash that chemically strips a layer of plaster off. This is usually not a DIY job unless you have a small pool or spa. Typically contractors who install polished finishes like Durazzo Polished Marble Pool Finish, Hydrazzo Polished Marble Pool Finishes, and Pebblesheen finish, have the polish equipment for the job.

DRP Tools describes How To Fix (Resurface) Rough Pool Plaster. They also sell the diamond polishing pads needed. They have a Pool Plaster Stain Remover Block to hand sand and remove stains. And they have plaster application tools.

Coyote Abrasives sells the Red Coyote Hydrotorque Pool Plaster Polisher as well as a selection of diamond grit pads and hand polishing pads.

YouTube videos on plaster polishing include:

• San Diego Pool Plaster Polishing
• Polishing a pool
• polishing a pool finish
• The Red Coyote Pool plaster polisher!