11 Time-Tested Secrets to Authentic South Indian Filter Coffee

5. Master the Water Temperature Sweet Spot

Water temperature affects extraction more than most people realize. For a proper decoction, use water just off the boil—aim for 92–96°C (195–205°F). If you bring water to a full boil, let it sit 30 seconds before pouring into the filter. Water that’s too hot can scorch the coffee and taste bitter; too cool yields weak, under-extracted decoction. If you don’t have a thermometer, bring water to a rolling boil, remove from heat, and wait about 20–30 seconds before adding to the coffee bed. Hard or heavily chlorinated tap water can mute flavors, so use filtered water if possible. Soft water exaggerates acidity while very hard water can make the cup dull; if your town’s water has a strong taste, bottled spring water with moderate mineral content is a safe alternative. Consistent temperature control leads to predictable decoction strength and a cleaner final cup.