Lunch Box Care: How to Clean and Look After a Stainless Steel Lunch Box

How do you clean a stainless steel lunch box every day?

The routine that prevents most problems is short: empty it, wash it, dry it completely. Food residue and trapped moisture cause most odours and spots.

Rinse the container and lid as soon as you can after eating. Dried-on sauce and starch take far more scrubbing than fresh residue.

Then wash both in warm water with ordinary washing-up liquid and a soft sponge or brush. Pay attention to the inside corners of the container and the channel around the lid's gasket, where residue collects out of sight. Give every part the same wash before you use it for the first time.

• Wash the lid and the container separately, so water reaches the gasket channel.
• Use a soft sponge, a nylon brush or a non-scratch pad, not wire wool.
• Rinse well, so no soap film is left on the steel.
• Dry with a clean tea towel, then leave the parts apart to air-dry fully.
• Store the container with the lid off or resting loosely on top, so moisture isn't sealed in.

How do you get smells out of a stainless steel lunch box?

Start by finding where the smell actually is. Stainless steel is non-porous, so it resists holding odours. A smell that survives a proper wash usually comes from a thin oily film left on the steel, or from the lid's silicone gasket, which can absorb oils and strong aromas such as garlic, curry and fish over time.

For the steel, bicarbonate of soda is the gentle first step. It's a mild alkali and a very fine abrasive, so it loosens oily films and neutralises acidic odour compounds. Rub a paste of bicarbonate of soda and a little water over the inside, leave it for about 15 minutes, then rinse and dry. For a stronger smell, soak the container in warm water with a couple of tablespoons of bicarbonate of soda dissolved in it.

If a fishy smell hangs on, try white vinegar next. Much of a fishy smell comes from alkaline compounds, and a mild acid neutralises them. Wipe or soak with equal parts white vinegar and water for a few minutes, then rinse and dry. Use the two treatments one after the other, never mixed, because they neutralise each other.

One warning: some advice suggests baking silicone to drive out smells. Never do that with a lunch box lid. The lid never goes in an oven, because its polypropylene frame softens at oven temperatures.

Do stainless steel lunch boxes rust?

Stainless steel resists rust, but it isn't immune to it. Its protection comes from chromium, which reacts with oxygen to form a very thin, invisible oxide film that shields the iron underneath and re-forms by itself when scratched. Orange or brown marks on a lunch box are usually one of the three things listed below. Only rust transfer is foreign material sitting on the surface. Tea staining is shallow, cosmetic corrosion of the steel's surface, and pitting is deeper, localised corrosion.

Chlorides are the common thread. Chloride ions, from table salt, salty brines and marinades, and chlorine bleach, can break down the protective film at a single point. That's why the standing advice for stainless steel is to rinse salty residue off promptly, keep bleach away from it, and never leave it sitting wet.

To remove surface spots, rub on the bicarbonate of soda paste described above, or a gentle cleaner made for stainless steel; some are based on oxalic acid, which dissolves rust deposits. Work gently with a soft cloth, rinse thoroughly and dry. If your container has a brushed finish, rub along the grain lines. Skip wire wool: it leaves behind the very iron particles that cause rust transfer.

• Rust transfer: tiny iron particles deposited on the surface from wire wool, a rusting dish rack or other items in the dishwasher. The particles rust, not the container, and the marks clean off.
• Tea staining: light surface corrosion that shows as a brown discolouration where salt and moisture sit on steel. It's cosmetic, doesn't go deep, and cleans off.
• Pitting: tiny dark pinpoints that don't wipe away. This is real, localised corrosion, usually from chlorides left on wet steel for long periods.

How do you clean the lid and the silicone gasket?

The gasket is the silicone ring that sits between the lid and the container, and it's the part of a lunch box that needs the most attention. Food and water work into the channel it sits in, and a gasket that goes back in damp is where smells and dark spots start.

If your lid's gasket is designed to come out, ease it out of its channel with a fingertip or a blunt tool, never a knife, which can nick the silicone. Wash the gasket and the channel in warm, soapy water, with a small soft brush for the groove, and soak the gasket in the bicarbonate of soda or vinegar solution above if it smells. Let every part dry completely, then press the gasket back in evenly so it sits flat. If the gasket isn't meant to come out, clean around its edge with a soft brush.

Treat the glass lid gently: glass can crack under a sudden temperature change, so don't run a hot lid under cold water.

A gasket that is torn, cracked, hardened or stretched so it no longer sits flat, or one where dark spots and smells return after thorough cleaning, is due for replacement: a gasket that doesn't seat evenly won't close the lid properly. On SEIDO lunch boxes, the lid parts — the tempered glass, the plastic frame, the clips and the silicone gasket — are covered for 1 year, because they wear with daily use, and the stainless steel containers for the full five years of the 5-Year Limited Warranty.

Can SEIDO lunch boxes go in the dishwasher?

Yes. SEIDO's lunch box containers are dishwasher safe, hand wash recommended, lab-tested to EN 12875-1 over 50 cycles. The lid goes on the top rack, per the manufacturer's care instructions.

Hand washing is recommended because it's gentler. Dishwasher detergents are harsher than washing-up liquid, and over many cycles they are harder on a lid's plastic and silicone parts. If a container comes out looking different, the colour tells you the cause.

• A white or cloudy film is mineral deposits from hard water, or detergent residue. Wipe with the vinegar solution from the smells section, rinse and dry.
• Rust-coloured specks are usually rust transfer from other items in the load, or dishwasher salt spilled into the wash. Clean them off as described in the rust section, and wipe up any spilled salt around the salt compartment.
• A rainbow sheen is usually a thin film of minerals or detergent. Wipe with the vinegar solution or a stainless steel cleaner, rinse and dry.
• A straw-to-blue tint that won't wipe off is heat tint. It forms only when steel is heated strongly, for example on a hob or in an oven, never in a dishwasher. It's cosmetic.

What are the rules for the microwave, the oven and the freezer?

Care includes using each part within its limits. The container was lab-tested in a 1000 W microwave: reheat with food in the container and the lid off, in a microwave of up to 1000 W, one container at a time and clear of the walls — never empty and never overfilled. Lid off is recommended; if the lid stays on, its steam vent must be fully open and clear, with food at least 1 cm (1/2 in) below the rim so nothing touches the lid.

In the oven, the container only: it was lab-tested for oven use without its lid, and the lid never goes in an oven. The container and the lid both go in the fridge and the freezer; leave headroom when you freeze liquids, and let a hot container cool before you put the lid back on.

• Microwave: container lab-tested; lid off, max 1000 W, never empty or overfilled.
• Oven: container only, lab-tested without its lid; the lid never goes in.
• Fridge and freezer: container and lid; leave headroom for liquids.
• Dishwasher: dishwasher safe, hand wash recommended; the lid on the top rack.

What wears out on a stainless steel lunch box, and what doesn't?

The steel body is the long-lived part. Everyday washing doesn't wear the steel away, and 304 (18/8) stainless steel resists staining and resists holding odours, so a well-kept container can stay clean-looking and clean-smelling for years. Expect cosmetic changes instead: fine scratches from cutlery and scrubbing, and dents if it's dropped. A dent near the rim is the one to watch, because it can stop the lid from sitting flat.

The lid is where wear happens. Silicone gaskets harden and stretch with age, and plastic frames can scuff or crack, so the lid is the part to treat most gently.

Our stainless steel lunch box 3-pack is designed for this daily routine at the office, the gym or on the commute: three 800 ml (27 oz) containers, each 304 (18/8) food-grade stainless steel, with glass lids in a polypropylene frame with a silicone gasket. The containers are dishwasher safe, hand wash recommended, and the set is backed by a 5-Year Limited Warranty (lid parts: 1 year).