Most people think of fire media as decoration — something to fill the burner area and make the flame look good. That’s part of it, but fire media is actually doing real functional work inside your fire table that affects how safe, clean, and consistent your flame is. Choosing the wrong type, or filling your burner area incorrectly, can cause problems that have nothing to do with how it looks.

Here’s a practical breakdown of the main options — fire glass, natural lava rock, tumbled lava rock, and ceramic lava rock — and what actually matters when you’re deciding what to use.

What Fire Media Actually Does

Before comparing materials, it helps to understand what fire media is doing in the first place. A gas fire table has a burner — a pipe or ring with ports that release gas. The media sits on top of and around that burner. Its job is to distribute the gas evenly as it rises through, so you get a consistent flame across the whole surface rather than jets of fire shooting out of specific spots.

Propane and natural gas behave differently here. Propane is heavier than air, so it tends to sink and pool at the bottom of the burner cavity. Natural gas is lighter than air and rises on its own. That difference matters when you’re thinking about media depth and layering — with propane especially, you want enough media to help the gas disperse before it reaches the flame, rather than pooling unevenly.

Beyond gas distribution, fire media also absorbs, retains, and radiates heat — which affects how warm your fire table actually feels to the people sitting around it.

Lava Rock: Natural, Tumbled, and Ceramic

Lava rock is the most common fire media and comes in a few different forms.

Natural lava rock is volcanic stone — porous, lightweight, and excellent at absorbing and slowly releasing heat. It comes in irregular shapes and earthy tones (black, red, brown) and gives a fire table a rugged, organic look. It’s typically the least expensive option and does a good job distributing gas. The downside is that it gradually breaks down over time, leaving fine dust particles in the burner area that need to be cleaned out periodically.

Tumbled lava rock is natural lava that’s been rounded and smoothed, similar in appearance to river rock. It comes in sizes ranging from about 1″ to 3″ and has a cleaner, more contemporary look than jagged raw lava. It retains the same heat properties as natural lava but presents better — the smoother surface makes it easier to clean and gives the fire table a more finished appearance when the flame is off.

Ceramic lava rock is a manufactured alternative to volcanic stone. It’s designed to mimic the look of natural lava while offering more size and color consistency. Ceramic media tends to hold its shape longer than organic rock and won’t leave the same dust residue. It’s a good option if you want a clean, uniform look without the maintenance that natural lava requires over time.

One sizing note: lava rock pieces should be at least ½” in diameter. Anything smaller can work its way into burner ports and restrict gas flow — which causes uneven flames or, in some cases, gas buildup.

Fire Glass

Fire glass is tempered glass that’s been tumbled to remove sharp edges, then used as fire media. It comes in a wide range of colors and sizes and reflects the flame in a way that lava rock can’t — the visual effect is genuinely striking, especially at night. It also radiates more heat than lava rock because of its reflective surface, making it one of the more efficient media choices from a warmth standpoint.

Quality matters significantly with fire glass. Properly tempered fire glass is designed to handle sustained heat without cracking, popping, or discoloring. Cheap or non-tempered glass isn’t — and when low-quality glass absorbs heat and releases moisture, it can pop. That’s not a catastrophic failure, but it’s annoying and means you’ll be replacing media more often than you should.

The other issue is blackening. Fire glass turns black when the gas isn’t burning completely — usually because gas flow is restricted, the burner is improperly tuned, or there isn’t enough airflow. A clogged burner or too-deep a layer of glass can cause incomplete combustion, and soot collects on the glass surface. This is more of a setup and maintenance issue than a material flaw, but it happens more visibly on glass than it does on dark lava rock.

Why We Don’t Recommend Filling Your Entire Burner Area with Glass

It’s possible to fill a fire table burner cavity entirely with fire glass, and plenty of people do it. But we’d push back on that approach for a few reasons.

A full glass fill makes it harder to see whether your burner is functioning correctly. If gas distribution isn’t even, the flame pattern tells you — but that’s easier to read when you’re not looking through several inches of reflective glass. Ventilation is also a factor. Tightly packed glass with no variation in material can restrict the upward flow of gas, leading to inconsistent flames.

And because glass shows everything — soot, dust, water spots — a full glass fill requires more frequent cleaning to maintain the look you bought it for. That’s not a deal-breaker, but it’s worth knowing going in.

The Layered Approach

The most practical setup for most fire tables is a base layer of lava rock — either natural or tumbled — with fire glass on top. The lava rock handles the functional work: gas distribution, heat absorption, and burner protection. The glass sits on top for the visual payoff. You get the reflective, colorful flame effect without filling the entire cavity with glass, and the lava base keeps everything burning cleanly.

A common ratio is to fill about two-thirds of the burner cavity with lava rock and top it with 1–2 inches of fire glass. That’s enough glass for the flame to catch and reflect across the surface without burying the burner entirely.

What We Carry

CastinCrete carries fire media to go with our GFRC fire tables — including fire glass and lava rock options. If you’re ordering a fire table and aren’t sure what media makes sense for your setup, we’re happy to walk through it with you before the order goes in. Call us at (262) 501-9966 or stop by the showroom in Hartland.