Use your fingers or a microfiber cloth to scrub the brass. However, don’t use anything abrasive, or you could scratch the surface.

If you can, try to use a bowl that’s not much larger than the item you’re cleaning. If you use a very large bowl, you’ll likely need to use a lot more ketchup to cover the object.

To clean a hollow object like a cup or a thimble, you may want to pour or rub a little of the ketchup inside the item before you coat the outside. That way, you can be sure the inside is evenly covered as well. If you’d prefer to use less ketchup, squirt a little of the condiment onto the object you’re cleaning, then use your fingers or a cloth to spread it completely over the object.

It should take about half an hour for the ketchup to break down a moderate amount of tarnish, but heavier tarnish might require an hour or even 2 hours. On the other hand, the ketchup might remove very light tarnish after 15 minutes or so.

Be sure to thoroughly wash away the ketchup or it might leave a sticky residue on your object.

If you’d like to help protect your item against future tarnishing, add a few drops of mineral oil or linseed oil to your cloth, then rub the oil onto the surface of the object.

Mild dish detergent is great for gently cleaning brass. Don’t use anything abrasive like steel wool or a rough cloth, or you could scratch the brass.

A shallow bowl or an old takeout container will work best for this, since it will be easy to dip the ketchup out of the container as you’re cleaning.

If you apply too much ketchup, it might drip off of the item. If that happens, wipe the ketchup immediately so it doesn’t become dry or stain anything. For very large pieces, like brass furniture, it may be easiest to work in smaller sections. Try using an old toothbrush to get the ketchup into any little nooks and crannies on the object.

Check the piece every 15 minutes or so until you’re happy with how the brass looks.

For big jobs, you might need to rinse out the cloth and add more soap whenever the cloth gets completely covered in ketchup. Be sure to completely wipe the ketchup away, or else it could leave a sticky residue.

Try rubbing a little mineral oil or linseed oil onto the surface of the brass to help slow the tarnishing process in the future!