Keep ceremonial-grade matcha in an airtight tin in the fridge and use it within two months of opening. The bigger tin may tempt you, but buy the smallest size you can find. Pre-sift the week's portions into tiny jars on Sunday so weekday mornings stay five minutes. The whisked matcha concentrate keeps in the fridge for up to 24 hours for iced lattes, but it loses brightness, so make hot cups fresh. If a cup turns bitter, the water was too hot — let the kettle rest a full two minutes next time and add an extra drizzle of maple to salvage it.