TSA liquid rules, plainly stated

The TSA's 3-1-1 rule covers anything that flows, spreads, sprays, smears, or pours. If it doesn't hold a solid shape at room temperature, it counts as a liquid.

The rule, briefly.

• 3.4 ounces (100 ml) per container
• 1 quart-sized clear bag
• 1 bag per passenger

Containers larger than 3.4 ounces go in the checked bag, even when they are nearly empty. The agent reads the label, not the level.

Where travelers get caught.

Mascara, lip gloss, lotion, deodorant gel, peanut butter, mayonnaise, yogurt, soft cheese. All liquid by the TSA's definition. Stick deodorant, bar soap, powder foundation, and most dry shampoos pass as solid. Aerosols, including hairspray and spray sunscreen, fall under 3-1-1 and need to fit in the quart bag with everything else.

Exceptions worth knowing.

Prescription medications and infant formula are exempt. Declare them at the checkpoint. Frozen items pass if they are fully frozen at the bin. Any slush reads as liquid.

The packing question is structural. A quart bag holds roughly nine 3.4-ounce bottles when they stand upright. The Lucent and Valence each ship with a water-resistant wet/dry pocket built into the lid. That pocket is where the quart bag belongs in transit. It seals the rest of the case from a leak and pulls out cleanly for the bin.

A small field test before any trip. Pack toiletries. Place the quart bag in the wet/dry pocket. Open the bag at security in under five seconds. If the system holds up, the trip starts well.

The rule has held at 3.4 ounces for years. Confirm at tsa.gov before the next departure if it has been a while.