Cleaning oven racks is probably one of the least popular household chores. It is messy and tedious to try to scrub off bits of cooked food or remove food stains that may have attached themselves to the racks over time. However, there are several simple and effective cleaning methods, one of which works especially well.
Most ovens have two large racks, so you will need an area that is big enough to accommodate the racks for a thorough cleaning. One possibility is the bathtub, taking care to avoid scratching the tub enamel by laying down an old sheet or towel under the racks. However, if you have a container big enough to hold the racks, this might be a better option because you could then do the cleaning, say, in the backyard.
One school of thinking recommends placing the racks in very hot water and washing powder, and leaving them to soak for several hours or overnight so that most of the grit will come off by itself. Other methods call for soaking the racks in a mixture of soapy, dish detergent water with vinegar added to it, or in ammonia (see references). You can also spray clean oven racks and leave them for several hours or overnight. Then wash and rinse the racks and leave them to dry. If you spray clean, do so in the open air because spray fumes can be very intense. It is also advisable to wear gloves, and to rest the racks on old newspaper to catch the residue.
In my personal experience, the soaking method with washing powder works best. But even so, to get oven racks totally spotless you may have to use a steel wool soap pad to remove any stubborn remnants. Keep the steel wool pad as a last resort, but be prepared to use it, if even after overnight soaking, the racks are still in need of further work. Having slaved to clean the oven racks, make an important new resolution: from now on, wipe up oven spills and stains as soon as they happen.