Lime cordial is sweetened, preserved lime — lime juice and lime peel cooked with sugar into a syrup stable enough to keep on a shelf. It is the older, stranger cousin of fresh lime juice, and the one ingredient that makes a Gimlet a Gimlet rather than just a gin sour.
Cordial Versus Juice
A Gimlet made with fresh lime juice and simple syrup is a perfectly acceptable drink, but it is not a Gimlet — it is a gin sour with a lime accent. The cordial brings something fresh juice cannot: a rounder, slightly confected sweetness from the cooked peel oils, a softer acidity, and a shelf life measured in weeks rather than hours.
This was the original point. Lauchlin Rose patented sweetened lime juice in Edinburgh in 1867 as a way to give Royal Navy sailors their daily lime ration without the cask of fresh fruit spoiling at sea. The drink built on it — gin and lime cordial in a stemmed glass — was the Gimlet, and Raymond Chandler would later write the canonical line about it in The Long Goodbye: "A real gimlet is half gin and half Rose's lime juice and nothing else. It beats martinis hollow."
The Build
The modern bartender's cordial is a step up from the bottled stuff. Fresh lime juice and fresh lime peel cooked briefly with sugar produces something cleaner, brighter, and more lime-forward than the commercial version, while keeping the shelf-stable convenience that is the whole point of a cordial.
Peel First
Zest the limes before juicing — the oils in the peel are where most of the lime's aromatic complexity lives, and a juice-only cordial tastes thin by comparison. Use a Y-peeler or microplane; avoid the white pith underneath, which is bitter.
Sugar and Acid
The ratio is roughly 1.5 cups sugar to 1 cup juice to a generous handful of peel. The high sugar concentration is what gives the cordial its shelf life — the same logic as jam. Cook gently to dissolve; do not boil hard, which drives off the volatile aromatics that make the cordial worth the effort.
Storage and Shelf Life
Strained into a clean jar and refrigerated, a fresh cordial keeps about three weeks before flavour begins to dull. The commercial Rose's bottle keeps for months because it contains preservatives the home version does not — that trade-off is the whole reason to make your own.
Bottom Line
If you make Gimlets — and especially if you make them for guests — keep a small jar in the fridge. A Gimlet with fresh cordial is a different drink from a Gimlet with Rose's, and a much better one. The technique transfers: the same method works for grapefruit, lemon, or yuzu cordials.