Lava rocks, often used for their aesthetic appeal and heat retention properties, raise questions about their safety, particularly regarding the possibility of them exploding. While these porous volcanic rocks do not detonate like explosives, they can fracture or splinter with considerable force under specific circumstances. Understanding the scientific principles behind this behavior is important for anyone using them in applications like fire pits or grills.
The Science Behind Potential Splintering
Lava rocks splinter or “pop” when heated due to trapped moisture. Formed from solidified molten lava, their porous texture, with numerous small holes from escaping gases, allows water to be absorbed and held within internal cavities. When water-laden rocks are subjected to rapid heating, such as being placed directly into a hot fire pit or grill, the trapped water quickly converts into steam. Steam occupies significantly more volume than liquid water, leading to a rapid increase in internal pressure. If this pressure builds too quickly for the rock’s porous structure to accommodate or release, the rock can fracture violently, expelling pieces.
Common Scenarios for Lava Rock Splintering
Certain situations increase the risk of lava rock splintering. Rocks that have been exposed to moisture, whether from rain, high humidity, or being submerged in water, are particularly susceptible. Even seemingly dry rocks can retain hidden moisture deep within their pores.
Rapid temperature changes also play a role in creating hazardous conditions. Placing cold or damp lava rocks directly into an already hot fire or grill causes the internal water to flash to steam almost instantaneously, leading to a sudden pressure buildup. This is most common in fire pits and gas grills, where lava rocks are frequently used and exposed to intense, direct heat.
Safe Handling and Use
Several practical precautions minimize the risk of lava rock splintering. Ensure lava rocks are thoroughly dry before heating. If rocks have been exposed to moisture, allow them ample time to air dry, or, for new or stored rocks, gradually heat them over a low flame for an extended period to allow any residual moisture to escape slowly.
Regularly inspect lava rocks for any visible cracks or damage, as these can become weak points where splintering might occur. When operating fire pits or grills containing lava rocks, maintain a safe distance, especially during initial heating, as popping sounds or flying fragments can occur. Wear protective eyewear to safeguard against unexpected rock fragments.