Guides
Why does stainless steel go rainbow-coloured, and how do you remove it?
The short answer: the rainbow colours are heat tint, a very thin layer of oxide that forms on stainless steel when it gets hot, and it is completely harmless. Wipe it off with a splash of white vinegar or a stainless steel cleaner and the pan is silver again in under a minute.
What causes the rainbow
Stainless steel stays stainless because of chromium, which forms an invisible protective oxide film on the surface. When the pan gets hot, that film thickens slightly. Once it is a few tens of nanometres thick, it starts to bend light the way a film of oil on a puddle does, and you see bands of gold, bronze, purple and blue. The colour tells you roughly how hot the steel got: straw and gold first, then brown, then purple and blue at higher temperatures.
It shows up most after:
- searing over a high heat, especially with the pan empty for a while;
- a long spell in a hot oven;
- boiling starchy water, such as pasta or potatoes, in a saucepan.
It does not affect how the pan cooks, and it does not flavour food. If you are happy with a slightly golden pan, you can leave it.
How to remove rainbow heat tint
Let the pan cool to warm.
Pour in a splash of white vinegar, around 2 tablespoons, or apply a stainless steel cleaner.
Wipe it round with a soft cloth or sponge. The colour lifts almost immediately.
Rinse with warm water and dry.
For tint on the outside of the pan, wet a cloth with vinegar and wipe. Avoid wire wool: it scratches the surface and leaves it duller.
White spots and a cloudy film
Chalky white spots or a cloudy film are a different thing: mineral deposits from hard water, or starch left behind after boiling pasta, rice or potatoes. London water is hard, so most of us see this. The fix is the same as for heat tint. Pour in a little white vinegar, or bring a 1 to 1 mix of water and vinegar to a simmer for a minute, then wash and dry. Drying the pan straight after washing stops the spots coming back.
Burnt-on food and brown stains
For stubborn brown marks, burnt fat or a scorched sauce:
Cover the base with water, bring it to a simmer for 5 minutes and scrape gently with a wooden spatula. Much of it will lift.
For what remains, mix bicarbonate of soda with a little water into a thick paste.
Spread it over the mark and leave it for 15 to 20 minutes.
Scrub with a non-scratch sponge, rinse and dry.
If a really stubborn stain still will not shift, do not worry and do not attack it with anything abrasive. Keep cooking and washing as normal: in our experience it fades naturally over time.
A full routine for everyday cleaning is in how to clean a steel frying pan.
How to see less of it
- Preheat over a medium heat rather than high. A pan with an aluminium core, like Season Tri-Ply, gets hot enough to sear without being blasted.
- Do not leave an empty pan on a high flame.
- Salt pasta water once it is boiling, not while it is cold, which helps avoid small pits in the steel.
- Dry the pan after washing.
Built for a lifetime of cleaning
The Season Tri-Ply Stainless Steel Frying Pan, £50 to £75, and the Season Tri-Ply Saucepan, £60 to £70, have 18/10 stainless steel inside and 430 steel outside, with no coating to protect, so vinegar, bicarbonate paste and the dishwasher are all fine. Both are oven safe to 240°C, work on all hobs including induction, and come with a 10 year warranty. To see how they are built, read what is tri-ply cookware? If the oven left the tint, can stainless steel pans go in the oven? covers temperatures.
Questions people ask
Is the rainbow on my stainless steel pan safe to cook on? Yes. It is a thin layer of oxide, part of the steel's natural protective film, and it does not affect food.
Does the rainbow mean I have ruined the pan? No. It means the pan got hot. It wipes off with vinegar and the pan cooks exactly as before.
Can I use lemon juice instead of vinegar? Yes. Any mild acid works; lemon juice does the same job.
Why does my saucepan go cloudy after boiling pasta? That is starch and minerals from the water, not heat tint. A splash of vinegar clears it.
Will the dishwasher remove heat tint? Not usually. A quick vinegar wipe is faster and more reliable.
What if a stain will not come off? Leave it. With everyday cooking and washing, stubborn marks fade naturally over time.
Cook like it matters.
From the cooks at Season, a London cookshop since 2005.