Wash the limes, then zest them all with a microplaner and save to a bowl.
Juice all the limes then weigh the juice out. Mine came to 460g. I added 50% of that weight in sugar (you can add up to 100% depending on your sweet tooth, but I think 50 is enough) so that came to 230g.
Pour the juice over the zest and mix in the sugar until it's dissolved.
I used some citric acid to act as a preservative, and dissolved 2 tsp into 230g (half the juice content) water, then poured that into the lime and zest.
Cover and leave overnight to infuse.
Next day, strain through a fine mesh sieve into a bottle and store in the fridge.
