I recently started using starch when I sew, but I don’t like the high cost, scent, and chemicals in commercial starch, so I make my own. Starching fabric adds preparation time, but makes sewing easier, and you get permanently crisp creases on hems, collars, and pockets, rather than the puffy home made look. I’ve been using starch to press up hems so they require less pinning, make jersey knits easier to handle, and to temporarily glue pockets in place before I sew them on. Quilters often starch their fabric, too. The starch washes out quite easily once you are done sewing.
I have posted recipes for home made laundry starch. You can take it a step further and extract your own starch from potatoes. Or two steps further and grow your own potatoes. Potato starch can also be used in gluten-free recipes and as a flour substitute for thickening gravies and sauces. And if you’ve got a bunch of potatoes that have turned green, you can still use them to make laundry starch.
To Extract Starch from Potatoes:
Either wash and scrub your potatoes well or peel them. Unless you want to use the starch for making laundry starch that will be used on white fabric, I see no reason to peel the potatoes.
Shred the potatoes finely. The finer you grate the potatoes, the more starch you will be able to get out. Cover the shredded potatoes with water in a bowl and stir them. I just let my kids stick their hands in there and play with the potatoes for a while.
Strain out the potatoes and save the water (which contains the starch) in a bowl or cooking pot. If you want to get every last bit of starch you can, wrap the potatoes in cheesecloth and squeeze them. Put the potatoes in some fresh water, swish them around, strain, and squeeze them again. Strain all of the liquid through cheesecloth or a very fine mesh strainer.
Let the liquid sit for a while undisturbed. Some people say to put it in the refrigerator and let it settle for a few hours. I am not that patient, so I just let it sit for about 45 minutes on the counter. Most of the starch has settled out by then. You might get another spoonful or so if you wait longer.
Slowly and carefully pour off the dark foamy liquid to reveal the layer of starch on the bottom of the bowl or pot.
I like to add some fresh water to the starch, stir it up, and let the starch settle out again. The water will be much clearer this time. Slowly pour off the water.
Scoop out the starch, spread it out on a baking pan, and leave it in a warm place to dry. Keep the starch below 110°F / 43°C as it dries. I like to stir the starch and smash it with a potato masher when it is partially dry to break up the clumps. If you live in a humid area and you are not sure your starch has dried completely, store it in the freezer.
From 9.5 pounds (4.3 kg) of potatoes, I got just over a half pint (200 g) of starch.
You don’t need to waste the shredded potatoes. Fry them up as hash browns or put them in soup. If you have more left over shredded potatoes than you can eat right away, you can dry or freeze them. Before drying or freezing, blanch the shredded potatoes briefly in boiling water, then cool in ice water.