Confirm the turkey is untreated and fully thawed. Fit a food-grade brining vessel inside the refrigerator with a rimmed tray below it. Keep the refrigerator at 40°F (4°C) or colder.

Heat 2 quarts of the measured water with the weighed salt, sugar, garlic, bay, rosemary, thyme and peppercorns. Stir about 5 minutes, until the salt and sugar dissolve; there is no need to boil vigorously.

Remove from heat. Add the remaining 6 quarts cold water and orange. Divide among clean containers if needed to cool efficiently. Refrigerate until the brine is at or below 40°F (4°C), allowing at least 2 hours and longer if needed. Temperature, not the clock, determines readiness.

Remove the neck and giblets from the thawed bird. Lower the turkey into the cold brine; keep completely submerged with a clean food-safe weight if needed. Cover and refrigerate for 12 hours, within the bird's existing 1–2-day refrigerated storage window. If more liquid is necessary, prepare and chill additional brine at the same ratio of 47.6 g salt per liter water.

Lift the turkey out without splashing. Discard the brine and aromatics. Do not rinse raw poultry; pat it dry and clean contacted surfaces. Roast using your preferred turkey method, checking for 165°F (74°C) in the thickest breast and innermost thigh and wing. Roasting time is not included here.