Ketchup as a cleaner: the pot trick that actually works (and where it does not)
The internet is full of “weird kitchen hacks” that fail the first time you try them. Ketchup on a tarnished copper pot is one of the few that works, and the reason is simple chemistry. If you have inherited a set of copper pans, or you own a brass candlestick that has turned brown, read on.
Why it works
Tarnish on copper and brass is a thin layer of oxidised metal. Ketchup contains vinegar (acetic acid) and a little salt, a mild combination that dissolves tarnish. The tomato does not do the cleaning; the vinegar does. This is the same idea as the classic lemon-and-salt method.
How to do it
You need ketchup, a soft cloth or sponge, warm water and a dry towel.
- Wash the item with ordinary dish soap first to remove grease. Ketchup will not clean through grease.
- Spread a thin layer of ketchup over the tarnished area. A thicker layer does not clean faster.
- Wait five to ten minutes. Do not leave it for hours; acid left on metal can leave marks of its own.
- Rub gently with a soft cloth in small circles. You should see the tarnish lift.
- Rinse well with warm water. Make sure no ketchup is left in seams or on handles.
- Dry immediately and buff with a clean towel. Moisture invites new tarnish.
For a stubborn pot, a second round works better than a longer wait.
What to use it on
- Copper-bottom pots and pans, on the copper part only
- Brass doorknobs, candlesticks and trays
- Copper mugs and serving bowls (rinse thoroughly and wash again before use)
What to avoid
- Lacquered or coated metal. If a copper item has a clear coating, acid can damage it. Check with a small test spot.
- Aluminum and cast iron. Acid can pit aluminum and strip the seasoning from cast iron.
- Antiques and heirlooms. Old patina can have value. A dealer or restorer will advise you before you scrub.
- Natural stone such as marble. Acid etches it.
- Using ketchup to clean items that touch food without a final wash. Always wash with soap afterwards.
Better options for bigger jobs
- Lemon and salt: cut a lemon in half, dip it in coarse salt and rub.
- White vinegar and salt paste with a little flour, for a more even finish.
- A commercial copper cleaner, if you have many items. They are more reliable on heavy tarnish.
Keeping copper bright
Once a pot is clean, tarnish comes back more slowly if you dry it right after washing, store it away from damp cupboards and avoid leaving acidic foods such as tomato sauce sitting in it. A quick rub with a dry cloth after each use is all most pans need. If you cook with copper, check that the inside is lined with tin or stainless steel; the cleaning in this article is for the outside only.
Preparing for guests
A shiny copper pot on the stove, a brass tray with snacks, a polished doorknob: these are small things, but guests notice a home that has been looked after. If you are hosting this weekend, set aside twenty minutes on Friday, put on music and clean three things. Nobody will say anything. Everyone will feel it.