If you like to cook using fish oil, then you may be interested in making your own pure fish oil at home. While this process is not practical if you wish to make fish oil in large quantities, you can use it to make small amounts for home medicinal remedies. Remember, most fish oil supplements have been refined to contain only the good parts of fish oil. Taking homemade fish oil may lead to a fishy body odor, nausea and belching.
Cut up the fish and remove the head and the tail completely. The rest of the fish can be cut into strips. If you like, fillet the fish. However, this is not necessary since you will likely not be able to eat the fish once it has been pressed anyway.
Press the fish pieces in the hand-crank press until just a watery, oily mush is left in the bottom of the press. Turn the crank until the press is as far down as it will go. You can then empty the fish sludge into a bucket of distilled water before pressing more fish in the press.
Strain the distilled water and fish mush. You can use a sieve or pour the mixture through a screen held over another bucket. Either way, the fish flesh, bones and skin will remain in the strainer, while the oil and water will pass through.
Allow the water to evaporate. Since oil and water do not mix, you can simply let the water evaporate off the bucket of oil-and-water mix. This will leave a whitish, greasy substance that is fish oil. If you are in a hurry, you can skim the fish oil off the top, but you will still need to allow some time for evaporation. Depending on the volume of water, you may need 1 day to nearly a week for all the water to disappear.
Place the bucket of oil and water in the sun for faster, natural evaporation.