Edible Glow Sticks

STEP 1: INFUSE THE CHAMOMILE

Heat the filtered water to 85C (185F) - hot but well short of boiling. Pour it over the dried chamomile flowers, cover, and leave to infuse for 8 minutes. Chamomile turns papery and bitter above about 90C, and bitterness is fatal in a component this transparent. Strain through a fine-mesh sieve without pressing the flowers, as pressing is the other route to bitterness.

STEP 2: SWEETEN AND SHARPEN

Stir the caster sugar into the warm infusion until fully dissolved, then add the lemon juice. Taste: it should read as sharp first and sweet second, with the chamomile sitting behind both, closer to a cordial than a tea. If it tastes rounded rather than bright, add the citric acid a few grains at a time, which lifts acidity without pushing the flavour toward lemonade.

STEP 3: CLARIFY

Pour the cooled infusion through a coffee filter paper into a clean jug and let it pass through at its own pace, around 15 minutes. The liquid should end up genuinely clear rather than merely strained. Suspended particles give dissolved CO2 somewhere to escape from, so a cloudy liquid loses its fizz far faster once disturbed - and filling a straw is exactly that disturbance. A clear infusion also carries light down the tube.

STEP 4: CHILL HARD

Refrigerate the clarified infusion for at least 3 hours, until it reaches 2-4C (36-39F). Cold liquid dissolves several times more CO2 than cool liquid, and this is usually where the difference lies between a straw that fizzes on the tongue and one that arrives flat. Chill the glass straws too, about 20 minutes in the freezer.

STEP 5: LOAD THE STRAWS

Working with one chilled straw at a time, drop in a mint leaf, then a raspberry, then a second mint leaf and a second raspberry, using a wooden skewer to seat each one gently without crushing it. Space them along the length rather than bunching them; the gaps are what make the tube read as a glow stick rather than a packed jar. Leave about 1 cm (1/2 in) clear at the bottom end and 2 cm (3/4 in) at the top, then stand the loaded straws upright in a chilled glass.

STEP 6: CARBONATE

Fill the siphon no more than two-thirds full with the ice-cold infusion. Seal, charge with one CO2 cartridge, and shake firmly for 20 seconds. Rest for a minute, charge with the second cartridge and shake again, then return the siphon to the fridge for 5 minutes so the gas goes fully into solution. If using a carbonation cap, squeeze the air out of a PET bottle before sealing, carbonate at around 40 psi, shake until the bottle stops accepting gas, and rest cold for 5 minutes. Release the pressure slowly either way, as a fast vent takes the carbonation straight back out.

STEP 7: FILL AND STOPPER

Working over a tray and quickly: hold a loaded straw upright, plug the bottom end with a fingertip, and dispense the carbonated infusion down the inside wall of the tube until it is full to about 1 cm (1/2 in) from the top. Pouring down the wall rather than straight in preserves far more of the fizz. Press a raspberry firmly into the top opening so it seats as a plug, then release your finger; surface tension and the stopper hold the liquid. Push a second raspberry into the bottom end if the bore is generous. Fill all six in sequence, taking no more than a minute in total.

STEP 8: SERVE IMMEDIATELY

Lay the straws on a tray of crushed ice, or stand them in a chilled short glass, and take them to the table at once; the carbonation does not wait. Tell people what to do with them - draw, do not bite, and finish on the raspberry at the end. Check every straw for chips before use and discard any that are damaged, and do not serve these to young children or to anyone who might bite rather than draw, as a whole raspberry seated as a plug is a choking risk if inhaled; clear food-safe tubing gives the same effect without the glass.