THERMAL SHOCK is not some new facet of climate change. It’s a very old phenomenon, but one so powerful it can split rocks. If you own a natural stone or porcelain countertop, you’ll want to be aware of the danger that thermal shock presents to your investment.

How does thermal shock affect countertops?

Thermal shock is defined by Collins Dictionary as “a fluctuation in temperature causing stress in a material” that “often results in a fracture.” That fluctuation can occur in a kitchen countertop when it comes into contact with a blazing-hot pan or a cooking appliance. Consider a real-life experience posted to one internet site.

We cracked a granite countertop from the heat of a crock pot. Sometimes it's all about thermal differential — at least it was for us. We left the slow cooker running all night during the winter where the house cooled off to the low 60's. Found the crack in the morning.

I thought my countertop was heat-resistant

The concept of thermal shock may seem puzzling to many homeowners. After all, one of the reasons people invest in porcelain or natural stone countertops is because they are notably heat-resistant. So why the problem when the heat gets turned up?

Think of two identical glasses side by side. One has just come out of the cupboard, the other has been in the freezer for hours. Boiling water is poured into both. The room-temperature glass is fine, but the frozen glass cracks. Why? The stress caused by the rapid change in temperature was too much for the frozen glass to deal with. It suffered thermal shock.

A sudden, drastic fluctuation in temperature can also cause thermal shock in stone or porcelain countertops — but honestly, this sudden scenario is rare. Thermal shock poses more of a risk to countertops when they are subjected to repeated, side-by-side differences of temperature over an extended period of time. What do we mean by side-by-side differences?

Imagine a crock pot, instant pot, air fryer or griddle placed on a granite countertop and cooking away. All around the appliance, the granite is heating up and expanding, but the rest of the countertop is cool to the touch. What do you think might happen when hot, expanding stone meets cold, stationary stone?

Of course, stone and porcelain are tough. They’re not going to shatter the first time you use an air fryer. But if you’re in the habit of using any kind of countertop cooker frequently, consider this observation from the International Surface Fabricators Association: “Cracks can be formed when the thermal stress of heat differential is repeated time and time again.” In other words, the constant heating and cooling of the same patch of countertop can eventually weaken it and cause it to crack.

How to prevent thermal shock

Thermal shock in countertops is 100% preventable. All you need to do is add a protective layer between your countertop and the heat source. Popular solutions include heat mats, trivets, and cutting boards. By taking this simple step, you not only protect your countertops from thermal shock, you help keep their protective sealant and shine intact.

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