Hands-on Plastering Education (w/ Jon Temple)

If you've ever wondered why some pool plaster jobs look flawless years later while others develop problems within months, you're about to discover the science-backed secrets that separate amateur work from professional mastery. In this deep-dive exploration of modern pool plastering, we'll uncover how cement chemistry has fundamentally changed in recent years and what leading plasterers are doing to adapt their techniques accordingly.

The Warranty-Driven Approach: Learning From 30 Years of Data

Most pool companies treat warranties as a necessary evil—something to minimize and forget about. But John and Johan Temple from Tempool in Jacksonville, Florida, have turned their warranty system into their greatest competitive advantage. Over three decades, they've meticulously tracked every callback, creating what might be the industry's most comprehensive database of plaster performance.

Every warranty we get, it's sent in on a form... We go through this whole thing, and we track what is warranty and what is service. Which crew did it? What time of year it was? What type of material it was? What type of color? The temperature? Was it raining? We keep track of all that.

— John Temple, Rule Your Pool Podcast

This isn't just recordkeeping—it's actionable intelligence. By analyzing patterns across thousands of pools, they've identified the root causes of today's most common plaster problems. Their data reveals that the biggest issue plaguing the industry right now isn't what most people think it is.

The Limestone Revolution: Why Your Cement Isn't What It Used to Be

Here's something most pool builders don't realize: the cement you're using today is fundamentally different from what was available just a few years ago. As part of a global initiative to reduce carbon footprint, cement manufacturers have begun incorporating significant amounts of limestone into Portland cement.

While this environmental initiative makes sense from a sustainability standpoint, it's creating unexpected challenges for pool plasterers. Unlike traditional cement components, limestone doesn't require kiln drying, making it cheaper and more environmentally friendly. However, it behaves very differently in thin plaster applications.

John Temple's field testing has revealed that the average bag of Portland cement now contains approximately 10.6% limestone. This seemingly small change has massive implications for how plasterers must adjust their mixing ratios and additive calculations.

The Dusty Pool Mystery: Residue vs. Calcium Hydroxide

One of the most frustrating problems pool owners face is the appearance of white, dusty residue in their newly plastered pools. For years, the industry assumed this was calcium hydroxide leaching from the cement. But Temple's warranty data tells a different story.

When we test our water chemistry, if our calcium levels don't change, we're ruling out calcium hydroxide. Well, what is that powder in the bottom of the pool? It's residue.

— John Temple, Rule Your Pool Podcast

The real culprit? Additive overuse. When plasterers calculate additive amounts based on the total weight of a cement bag without accounting for the limestone content, they're essentially adding 10-15% too much additive. This excess creates a residue that settles in the pool, mimicking the appearance of calcium hydroxide leaching.

This discovery highlights the importance of communicating with cement suppliers to understand the exact limestone content in each batch—information that most contractors never think to request.

Water-to-Cement Ratio: The Foundation of Everything

Perhaps no single factor influences plaster quality more than the water-to-cement ratio. Yet it's often the most misunderstood aspect of the mixing process. When plaster starts setting too quickly—whether due to limestone content, high temperatures, or other factors—the instinctive response is to add more water. This creates a cascade of problems.

Adding excess water might make the material easier to spread, but it fundamentally weakens the cement structure. More water means more shrinkage as the plaster cures, leading directly to check cracking—those hairline cracks that can appear within days of application.

Johan Temple, who has been perfecting his craft for nearly three decades, explains how they've solved this dilemma:

If you don't use as much water and you mix a thicker mix, your mix is mixed more thoroughly. It will dry quicker. If you add a lot of water to it, you've got to use something to help dry all that water out.

— Johan Temple, Rule Your Pool Podcast

Instead of adding water and then trying to remove it with accelerants like calcium chloride, they use only 0.3% calcium chloride and rely on high-powered fans to control the curing process. This approach eliminates the need for torches, which can actually stain pigmented plaster due to the butane they emit.

The Check Cracking Solution: Proper Mixing and Troweling Technique

Check cracking has plagued the pool industry for decades, with many considering it an inevitable part of the plastering process. The Temples have proven otherwise. Their test pool in Jacksonville—which remains empty and exposed to Florida's harsh weather conditions year-round—shows no check cracking even after six years.

The secret lies in understanding the relationship between mix consistency, troweling technique, and curing conditions. By maintaining proper water-to-cement ratios and employing what they call "compression hard troweling," they can consistently produce crack-free surfaces.

I can start with a material that's not going to check crack, make it check crack just by adding water and not troweling. Not giving it that compression hard trowel... If you can cause it to check crack, you know what's causing the check crack. So just don't do that and you won't have check cracking.

— John Temple, Rule Your Pool Podcast

This empirical approach—deliberately creating problems to understand their causes—exemplifies the scientific methodology that sets top-tier plasterers apart from the competition.

The Science Behind Interfacial Transition Zones

To truly understand why certain plaster problems occur, you need to think at the molecular level. When cement hydrates, roughly 25% of the material becomes calcium hydroxide. This process creates interfacial transition zones (ITZs)—weak areas where the cement meets aggregate particles like sand or pebbles.

These ITZs represent the most vulnerable points in any plaster surface. When pool water chemistry becomes aggressive (typically due to low LSI values), it targets these areas first, dissolving the calcium hydroxide and creating the white rings around aggregate that many mistake for normal "mottling."

By creating a tighter mix with proper water-to-cement ratios, plasterers can minimize the size and number of these vulnerable zones, creating more durable surfaces that resist chemical attack.

Revolutionary Washing Techniques: The Sodium Bicarbonate Game-Changer

The final piece of the plaster puzzle involves the washing process—how the surface is cleaned and prepared after curing. Traditional muriatic acid washing has been the industry standard for decades, but new understanding of cement chemistry has led to innovative approaches.

The introduction of sodium bicarbonate washing represents a paradigm shift in surface preparation. Unlike acid washing, which can etch and weaken the surface, bicarbonate washing provides a gentler approach that works particularly well with modern cement formulations and advanced technologies like Set and Cure systems.

This technique has become especially important as the industry adopts new materials and application methods. The combination of proper mixing, controlled curing, and appropriate washing creates a synergistic effect that dramatically improves long-term performance.

Practical Implementation: What This Means for Your Business

These insights aren't just theoretical—they represent actionable strategies that can immediately improve your plaster results. Here's how to implement these concepts:

• Communicate with suppliers: Request detailed information about limestone content in your cement to properly calculate additive ratios.
• Invest in proper equipment: High-powered fans for controlled drying are more effective and economical than torches.
• Document everything: Create your own warranty tracking system to identify patterns and improve processes.
• Focus on fundamentals: Perfect your water-to-cement ratios before experimenting with advanced additives.
• Train your crews: Ensure everyone understands the relationship between mixing, troweling, and final quality.

The pool industry is evolving rapidly, with new materials and techniques emerging regularly. However, success still depends on mastering the fundamentals of cement chemistry and application technique. By understanding these principles and adapting to modern materials, plasterers can consistently deliver superior results that stand the test of time.

Whether you're a seasoned professional looking to refine your techniques or a newcomer seeking to understand the science behind quality plaster work, these insights provide a roadmap for excellence in an increasingly competitive market. The key is combining traditional craftsmanship with modern scientific understanding—exactly what separates good plasterers from great ones.

Episode Chapters

• 00:00 Introduction to Hands-on Plastering Education
• 02:30 Warranty-Driven Quality Control System
• 08:15 Portland Limestone Cement Changes
• 12:45 The Dusty Pool Problem and Additive Issues
• 18:20 Water-to-Cement Ratio and Set Times
• 24:10 Check Cracking Prevention Techniques
• 30:45 Interfacial Transition Zones and Chemistry
• 35:30 Sodium Bicarbonate Washing Innovation