Two different ways to move heat
Ice does most of its cooling through latent heat of fusion. Turning one gram of ice into one gram of water absorbs about 334 joules — and it absorbs that energy at a constant 0°C, without the ice getting any warmer first. That is an enormous amount of cooling from a very small cube, and it is why ice is so effective.
The catch is built into the mechanism. Every joule of latent cooling produces a gram of water, and that water goes into your glass. There is no version of ice that cools this way and doesn't dilute.
Steel has no phase change to spend. It cools through specific heat capacityalone: a frozen steel cube at −18°C simply absorbs heat as it warms back up toward the temperature of the drink. That is roughly 0.5 joules per gram per degree — far less total cooling than melting, which is exactly why steel gets your drink cold rather than ice-cold.
What that costs, and what it buys
In a 60 ml pour, ice will typically add around 28% of its volume back as meltwater over half an hour. A 40% ABV spirit lands nearer 31%. Everything you paid for in that bottle — the cask character, the finish, the length — is now sitting in a third more liquid.
Steel gets the same pour to roughly fridge temperature and holds it there for about thirty minutes, with nothing added. You trade a few degrees for a drink that tastes the way the distiller intended. For carbonated drinks the trade is even more one-sided: meltwater flattens a mixer, and a non-porous steel surface gives dissolved CO₂ far fewer places to nucleate than the rough, pitted surface of a melting ice cube.
Why 304 stainless steel
304 is the austenitic alloy used for commercial kitchen benches, cocktail shakers and brewing tanks — roughly 18% chromium and 8% nickel. The chromium forms a passive oxide layer that re-forms if it is scratched, which is what makes the surface non-reactive and rust-resistant.
Our cubes are then electropolished, an electrochemical process that removes the microscopic peaks left by machining. The result is a surface with nothing for odours, oils or bacteria to lodge in — the reason steel cubes do not pick up freezer smells the way porous soapstone can.
What steel is not good at
Being straight about it: if what you want is the coldest possible drink and you do not mind dilution — a long summer soft drink, say — ice still wins on raw cooling. Steel is for the pours where dilution is the thing you are trying to avoid: spirits, wine, cold brew, anything carbonated, and anything you would rather sip slowly.