Glass coffee gear

Glass is the material you buy when you want to watch. In a glass French press, a cold brewer or a pour over dripper and carafe, seeing the bloom, the colour and the level is not decoration, it is how you know what is happening. It is also chemically neutral, so it adds nothing to the cup.

Borosilicate is the specification that matters

Ordinary soda-lime glass expands unevenly when heated and cracks from thermal shock, which is exactly what pouring boiling water into a cold vessel does. Borosilicate expands far less and tolerates the swing. Nearly all good coffee glassware is borosilicate and the makers who use it say so. A carafe that does not name its glass is worth a question, especially if it is inexpensive.

It holds heat badly, and that is often fine

Thin glass and a large surface area mean a glass press goes cold quickly. That is a real drawback if you brew a full press for two people, and no drawback at all if you drink it straight away. Insulated presses are the alternative and they cost you the sight of the brew, which is the whole trade.

Breakage is a running cost, not a disaster

On most French presses and drip machines the beaker or carafe is a replaceable part sold separately for a fraction of the whole. Before buying, check that the replacement exists and what it costs: a brewer whose glass cannot be replaced is one breakage from being landfill, and that is a specification worth as much as any other.

Where glass beats steel outright

Cold brew. A long steep at room temperature has no heat to retain, the process takes twelve hours and being able to see the colour tells you how it is going. It is also the easiest material to tell is genuinely clean, which after twelve hours of coffee in contact with the vessel is worth something.

What to check before buying

Whether it is borosilicate, whether the beaker is replaceable, and whether the handle assembly is separate from the glass. A press whose handle is bonded to the beaker turns a cheap breakage into an expensive one. Dishwasher safe is usually true of the glass and often not of the rest.