Glass Cookie Jar with Airtight Bamboo Lid, 76oz

Biscuits go soft for the same reason crackers do: they are dry, the air is not, and they will keep pulling moisture out of a room until they match it.

The lid seals against a silicone gasket, so the air inside stops exchanging with the kitchen. That is the difference between a jar and a decoration. Anything dry keeps: biscuits, crackers, dried fruit, coffee beans, dog treats.

The body is thick borosilicate glass. Glass because you can see what is left, which is the only reliable way anyone remembers to eat it, and borosilicate because it takes a temperature change without arguing.

Seventy-six ounces is a little over half a gallon. In practice that is two supermarket packets with room to get your hand in.

What it will not do

Glass resists heat well and impact badly. A knock against a stone worktop will chip the rim, and a chipped rim will not seal. Set it down rather than sliding it.

The bamboo lid is hand-wash only and will lighten with age. The gasket is the part that does the work, and it can be pulled out and rinsed when it needs it.

Why a bamboo lid rather than plastic or metal

A glass cookie jar with a bamboo lid is a slightly harder thing to build than one with a plastic screw top, and the reason to bother is what the lid touches. Plastic takes on the smell of whatever has been in the jar and keeps it. Metal is fine until it meets anything acidic and then it is not. Bamboo does neither, and a silicone gasket underneath does the sealing, so the wood never has to be the airtight part.

It is a wear part and it is not dishwasher safe. The glass is. That trade is set out in full in how to look after a bamboo lid.

One kind of thing at a time

The most common way an airtight cookie jar disappoints is not the seal. It is a jar with two kinds of biscuit in it. Inside a sealed jar the air settles at one humidity, so a chewy biscuit gives up its moisture and a crisp one takes it in, and both come out wrong. A better gasket makes that worse rather than better, because it lets them equalise more completely. Why that happens, and what to do instead, is in why cookies go hard and crisp ones go soft in the same jar.