Organic matcha is a hygroscopic powder—fancy way of saying it loves to absorb water from the air. If your tin has been open too long, or you're scooping with a damp spoon, you're inviting clumps. Even a few hours in a humid kitchen can start the process.

Fix: Keep your matcha in an airtight container, and if you live somewhere humid, store it in the fridge. Let it warm up to room temperature before opening to avoid condensation. Also, always use a dry spoon—never dip a wet one in.