Words can be funny things, they can mean different things to different people. I was talking to a man recently that claimed he hated science. "Scientists are all a bunch of know-it-alls that like to tell us how to do things," he told me. I just shrugged and said that it sounded like he was describing half the human race.
A true scientist knows they can never "know it all". If fact that is the basis of science. All theories should be tested over and over and over again by as many different people as possible in as many different situations as possible before they can be reasonably thought of as a working theory. But even scientific laws are nothing more than theories, because a true scientist knows that they will never be able to test their theory in every possible situation in the universe. Who knows, on a distant planet, gravity may not work the same way it works here on earth. Yet gravity is a scientific law, only for the fact that we have tested it in every way we know how and it has always tested true. If you meet a person who claims to be a scientist and says that their theories are always right, you are talking to a person who is not a true scientist.
The reason I bring this up is because as a homesteader, we are all scientists. We experiment every year with our gardens, our livestock, our cooking... Heck, for most of us, everything is an experiment. Some of those experiments will fail. It's just the nature of homesteading. If you can't stand making mistakes, homesteading is not the life for you. Because of these experiments, homesteaders have some of their own technologies. Some of these technologies are being forgotten in the modern world of letting others be our scientists for us.
When I was teaching a class on soap making from scratch last week, I told the group to always test their lye water in cabbage water before they started boiling it. If it didn't turn a greenish color, run the water through the ashes again because there wasn't enough lye in the water to make the boiling worth their while. The students, some of which had been making soap for many years from store bought lye, all looked at me like I was speaking Russian. Cabbage water? Why would they test their lye water in cabbage water?
This kind of shocked me at first. I've never made soap totally from scratch without pouring some boiling water over a few layers of a red cabbage. That was always my first step in fact. Red cabbage water is a neutral and a strong alkaline turns it greenish in color, meaning that the water we've just poured through the ash is strong enough to start boiling it down. If it doesn't turn green (usually it turns just a little blue) you need to either run it through the ash again or make sure your ash doesn't have any charcoal in it and start over. Charcoal can absorb the alkaline from the ash and then we would never get lye, no matter how long we boiled the water. Why waste all the fuel you are going to use to boil down your lye water if you're never going to end up with lye? Test it first.
Red cabbage as a litmus test has been used for many more things than lye for soap. Many people use it to test the water that will be used to make hominy. If the water isn't alkaline enough it can make maize actually bad for us to eat, causing a disease called pellagra. Untreated maize can rob our bodies of niacin so we need to treat it with an alkaline water to make it safe to eat. Red cabbage water is used to test garden soil to make sure that it is not too acid or alkaline to grow plants in. Red cabbage water is used to test vinegar to make sure it is not too acid or not acid enough, especially in canning. Foods high in acid can be canned safely in a boiling bath as apposed to a pressure canner. So for the old time homesteader, red cabbage was grown for more than just eating. It was part of the day to day science experiment that is the life of a homesteader.
To make red cabbage water simply take a few layers of a head of red cabbage (even the outer red area we usually throw away work) and pour boiling water over it. It's just like you're making red cabbage tea. If your water is very limey or has many chemicals in it, it probably won't work, you'll need distilled water then. After you let it let for a half an hour or so, put the cabbage leaves on the compost pike and keep the water in a cool place. You now have your very own litmus tester. If you like the idea of litmus paper, take white paper towel, soak it in the cabbage water, and let dry. Keep this is a sealed jar and use it whenever you need litmus paper to test how acid or alkaline something is.