Do not pour boiling hot coffee directly over ice. That’s a recipe for shattered glass and a sad, scalded tongue. Let it sit for a minute first, or use a heatproof glass. Safety first, coffee second.
Also, never (and I mean NEVER) microwave a glass of iced coffee to reheat it. You will either explode the glass or create a lava-hot pocket of misery. Just drink it cold or make a fresh cup.
If you do pour hot coffee over ice and hear a crack, that’s the sound of your morning being ruined. Be smarter than the glass. You got this.
