Making your own corn oil at home can be a somewhat slow and tedious process. However, if you raise your own corn and you want to give it a try, you can make corn oil in your own backyard. Of course, your yield will not be nearly as high as a corn oil manufacturer's, who has access to large-scale machinery and chemicals to help with the process, but you can be sure it will be all natural.
Fill the bucket or tub about a third full of water. Since you will be eating this corn oil, you might want to use purified or distilled water instead of water right out of the tap.
Press the corn. The mechanical press will crush the corn to a pulp as you turn the crank. By the time you have pressed the corn as far as it will go, you will have a runny, pulpy goo. This is just what you want. Each time that you press the corn, scrape the goo into the tub or bucket. The corn oil in the goo will float on top of the water and the pieces of the kernels will separate and float in the water. Continue pressing until all of the corn has been pressed and all of the goo is in the tub.
Strain out the corn pieces. Pour the contents of the tub through the screen into the other tub. This will filter out all of the kernels and corn pieces. You will be left with a corn oil and water mixture.
Set the tub of oil and water in the sun. Leave it covered with the screen so that bugs and leaves do not fall in. As the tub sits, the water will evaporate. This will leave a yellowish film in the tub that is pure corn oil. You can scrape it up with the rubber spatula and use it to cook with.
Speed the evaporation process by pouring the water and oil mixture into shallow trays, such as large cookie trays with a high lip.