For a fun end-of-the-season garden project, harvest some tomatoes and clean them for seeds. This may sound daunting, but it's not difficult. Any type of tomato will work, though hybrid varieties may appear changed somewhat when you grow them from the saved seed. Wait until the end of the summer to save tomato seed.
Prepping the Seed
Pick mature to overripe tomato fruits and remove the stem with a paring knife.
Slice the tomato in half lengthwise to expose the seeds, which will be visible and covered with a thick gel.
Squish the tomato between your thumb and forefinger to dislodge the gel-covered seeds. Squeeze the seeds into a bucket. Jerk your wrist to the side to help seeds slip from the tomato into the bucket. Remove all tomato seeds in this manner. Use the seedless remains of the tomatoes for sauce.
Pour the seed and juice mix into a container with a lid, such as a jam jar. Leave this container for two days to ferment lightly. You may notice mold growing in the jar; this is fine. After two days, the fermenting seeds are ready to be washed and cleaned.
Cleaning the Seeds
Uncap the jar and pour the seed mixture into a larger bowl or container. Add water and swirl the container. The seeds will settle to the bottom. Pour out the water and leave the seeds in the container. You'll notice less gel around the seeds.
Add fresh water and repeat the swirling process. Repeat this two more times or until the tomato seed is free of gel.
Pour cleaned tomato seeds onto a flat mesh screen or a few sheets of newspaper. Let them air dry for several days until they're completely dry to the touch. If you're drying the seed on a newspaper, you'll need to flip the seed from on side to the other; a screen allows both sides to dry easily.
When the seed is completely dry, store it in an air-tight container in a dark space until it's time to start your tomatoes the following season.