Fanning the coals
Clearing the stem.
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Clearing the stem.
Hookah stems are made of stainless steel, aluminum, brass, wood, or glass — the material sets weight, corrosion resistance, and how well the walls conduct heat.
Each material has its own set of physical properties, and one of them is regularly described inaccurately: it's a common claim that stainless steel cools smoke better than other metals, even though by pure thermal conductivity it's actually the worst heat conductor among them. Let's look at what's behind this contradiction and which figures back up the other claims about stem materials.
The stem connects the bowl, base, and hose — smoke passes through it and cools on its way from the coal to the water. That's where the requirements come from, and they don't depend on the specific metal: resistance to rust and corrosion, imperviousness to moisture, resistance to high temperatures and deformation, and no foreign smell when heated. Plastics and flammable materials don't meet these requirements — they aren't used for the stem itself, except in mouthpieces and decorative inserts.
Rust resistance comes from chromium: at a content of 10.5% and above, a thin passive layer of chromium oxide forms on the metal's surface and self-repairs on contact with oxygen, and any damage only affects the outermost layers of atoms. In terms of ease of cleaning, stainless steel outperforms copper and aluminum and is comparable to glass — which explains its use in the food and pharmaceutical industries.
Stainless steel's density is 7.5–8.0 g/cm³ depending on the alloy grade (composition: iron, chromium 12.5–25%, nickel 0–20%, molybdenum 0–3%). But its thermal conductivity isn't what you'd expect from a metal in the context of cooling: 16.3–24 W/(m·K) at room temperature — noticeably less than copper, brass, or aluminum. The same effect applies to electrical conductivity: an alloy conducts heat worse than a pure metal.
This is where the common description and reference physics diverge. Marketing materials and reviews often call stainless steel the optimal material based on its overall set of characteristics, without noting that by thermal conductivity it's the worst heat conductor among stem metals: 16.3–24 W/(m·K) versus 109–125 for brass and 204–250 for aluminum.
A specific and limited conclusion follows from these figures: stainless steel releases heat outward worse than brass or aluminum — this is a material property measured in a laboratory, unrelated to hookahs. Sources give no direct measurements of stem surface temperature or of smoke temperature at the mouthpiece depending on material — not for steel, not for other metals either. So it's accurate to talk only about the thermal conductivity of the material itself, not about how much colder the resulting smoke actually is: you can't carry one over to the other without a separate measurement.
A similar story applies to sellers' claims that a brass or copper stem cools smoke better, and that the longer the stem, the more noticeable the effect: this rests on a true fact — brass and copper genuinely conduct heat better than steel — but sources give no measured link between a metal's thermal conductivity and an actual difference in smoke temperature at the outlet.
Aluminum is roughly three times lighter than steel: its density is 2.70 g/cm³. Pure aluminum's thermal conductivity is 204–250 W/(m·K) depending on sample purity — roughly an order of magnitude higher than stainless steel.
Aluminum's weak point is chlorides: it corrodes under the action of chlorides dissolved in water, including ordinary table salt, and its protective oxide layer is also broken down by contact with mercury or salts of certain electropositive metals. Anodizing increases resistance to moisture and acids, but with prolonged submersion in water, anodized aluminum still starts to oxidize — hence the practice of storing the piece disassembled, since otherwise moisture builds up at the base.
Duralumin — an alloy of aluminum with manganese, copper, and magnesium from the same class used in rocket and aircraft engineering — gives a light, sturdy stem, but the construction is more sensitive to damage and less durable, especially if a manufacturer adds cheap impurities to the alloy.
Brass is heavier than both steel and aluminum: its density is 8.4–8.73 g/cm³, and its melting point is 900–940°C depending on alloy composition. Brass's thermal conductivity (for alloys with 63–70% copper content) is roughly 109–125 W/(m·K) — higher than stainless steel but lower than pure copper (385–401 W/(m·K), the highest figure among metals practically used for stems).
Brass has two specific failure mechanisms that steel doesn't have. The first is dezincification: selective leaching of zinc from the alloy, especially in soft, hot water and in the presence of chlorides; the result is a porous copper structure that has lost its mechanical strength. Separate "dezincification-resistant" brass grades exist for this exact problem in plumbing, containing small fractions of lead and arsenic that suppress zinc loss. The second mechanism is stress corrosion cracking from ammonia, known as "season cracking": historically this affected brass cartridge cases, which cracked from ammonia vapors when stored in stables.
Copper develops a greenish patina over time and requires upkeep. Brass and copper are used in stems less often than steel, mainly because of raw material cost; adding cheap impurities to the alloy, which manufacturers sometimes do, makes the construction more brittle and less corrosion-resistant, so in the end it can cost more than an ordinary stainless steel stem.
Wood absorbs odors and moisture — sources name this outright as a drawback for a stem material. Hence the practice with wooden hookahs: smoke a single flavor at a time without mixing, and disassemble the setup right after the session so the parts don't sit in water for long. Some European manufacturers build such stems with an internal metal tube, but such models cost more than ordinary ones.
Glass is easy to maintain and doesn't absorb outside odors; a glass stem's shape (for example, a spiral, sometimes about a meter tall while remaining compact in appearance) extends the smoke's path. All glass stems are handmade, so they're expensive and can't be repaired if damaged.
Polymers release odor and lose their properties when heated, and smoke cools poorly in such a barrel — so they're used more often for mouthpieces and hoses. Some manufacturers combine materials: a polymer exterior handles color, while a metal tube inside carries the functional role.
| Material | Density, g/cm³ | Thermal conductivity, W/(m·K) | Corrosion characteristics |
|---|---|---|---|
| Stainless steel | 7.5–8.0 | 16.3–24 | Passive chromium layer, self-repairing |
| Aluminum | 2.70 | 204–250 | Sensitive to chlorides (incl. salt), mercury |
| Brass | 8.4–8.73 | 109–125 | Dezincification, ammonia cracking |
| Copper (for comparison) | — | 385–401 | Patina on contact with air |
Brass's melting point (900–940°C) and all the thermal conductivity and density figures above are reference material properties, not measurements taken on finished hookah stems. Disassembling and drying after a session applies to all metals, but matters more for aluminum (moisture under the anodized layer) and brass (dezincification kicks in on contact with water); requirements are gentler for stainless steel thanks to its self-repairing layer.
Is it true that stainless steel cools smoke better? By thermal conductivity — the opposite: steel is the worst heat conductor among stem metals (16.3–24 W/(m·K) versus 109–125 for brass and 204–250 for aluminum). But this is a material property, not a measurement of smoke temperature — sources give no direct measurements taken on hookahs.
Which stem metal is heaviest? Brass (8.4–8.73 g/cm³) — heavier than both steel (7.5–8.0) and especially aluminum (2.70), which is almost three times lighter than steel.
Why is water risky for an aluminum stem? Because of dissolved chlorides, including ordinary table salt: they break down the protective oxide layer, which is why the piece is recommended to be stored disassembled and dry.
What is brass dezincification? Selective leaching of zinc from the alloy — especially in soft, hot water and in the presence of chlorides — leaving a porous, less durable copper structure.
Why aren't polymers used for the stem itself? When heated they release odor and lose their properties, and smoke cools worse in such a barrel — so they're used more often for mouthpieces and hoses, sometimes combined with an internal metal tube.
The stem's material is just one part of what makes up a hookah's overall cost: more on that in "What Makes Up the Price of a Hookah," and a broader guide to choosing one in "How to Choose a Hookah." What can be fixed at home if the stem or a thread is damaged is covered in "Hookah Repair and Spare Parts: What You Can Fix Yourself," while storing and transporting an assembled hookah between sessions is covered in "Storing and Transporting a Hookah."