As I mentioned in my previous post lye is a very caustic chemical that is used in many different processes. It can be purchased commercially as a powder, but it has become harder to find as retailers want to avoid selling it to people who use it to make street drugs. Also, when you mix solid lye (Sodium Hydroxide, or NaOH) with water it releases a lot of heat, potentially bringing the solution nearly to the boiling point. This, plus the fact that it gives off noxious fumes, means that making your own lye solution can be an attractive option.
The downside of making your own lye solution is twofold: first, you cannot be guaranteed a specific solution strength; second, you will not get pure Sodium Hydroxide, as the solution will include some Potassium Hydroxide as well.
The first issue can be at least partially resolved by using either a pH measuring device, or using some "old-tyme" methods for determining solution strength. The second can be partly controlled by the starting ingredients, which will be covered below. Many processes can use Sodium or Potassium Hydroxide nearly interchangeably, but Sodium is the preferable type.
The making of lye is so simple it was probably discovered by accident. It is a simple matter of soaking ashes from burned wood in rain water. Rain water is preferred because it has fewer chemicals that can interfere with the processes of leaching the lye from the ashes. This pertains to both ground water from wells and tap water, although for different reasons.
There are two main methods that I have seen: boiling and slow filtering. Of the two, boiling is simplest, but the results are not as good. Slow filtering requires a little more equipment, but I will be providing a link to site that shows an ingenious method of setting up an "automatic" lye solution making system. Once this is done it is a simple matter of keeping the ash hopper full, and you have a ready source of lye solution.
One word of caution: lye water, even when mild, can react to many materials. For this reason you need to be very selective in what you use to both store and collect your lye solution. Acceptable materials include plastic, glass and wood. Most metals are bad, most especially aluminum, so keep your pots and pans out of the equation unless you want to use a cast iron pot (pure iron does not seem to react to lye). Of course, a cast iron pot has many better uses than making lye; it would be a shame to waste it in such a manner.
The ashes you use for making lye can come from three general sources. The first is ashes from hard woods, which results in a good solution. I have heard that both oak and apple wood are particularly good. The second is ash from soft wood, such as pine and other evergreens. These result in weaker solutions, but they can still be used. For instance, in soap making, the hard wood ashes will result in a harder soap suitable for making bars, whereas the softwood ashes tend to result in soaps that stay in liquid form.
The third type of ash you can use is from seaweed (kelp). This is the strongest of the three, and results in a very potent solution. Kelp was used historically for this and other purposes, included the making of glass. If you can get some you may want to try it, but I should point out that your neighbors will probably not thank you, as it can be quite smelly. If you can burn it at the beach safely (and legally) and then bring the ashes home, that would be the best option.
The best method of leaching lye from the ashes is to use a filtration system in a wooden or plastic barrel. The bottom of the barrel should have holes to allow water to flow out, and there should be a catchment system to collect the liquid that pours out. In the bottom of barrel place a layer of gravel, and on top of this a layer of twigs, and then on top of that a layer of straw or hay. (Lawn clippings might work, but I have not tried it). Finally, on top of this goes your ashes, preferably filled nearly to the top. You now start pouring the rain water into the barrel, slowly so the ashes do not start floating.
Basically what you have a is a giant coffee machine, with the barrel acting as the filter and the ashes as the coffee grounds. The process is the same as making coffee: water leaches out the stuff you want from the stuff that it is running through. By slowing the water down we extract more of the lye from the ashes. Unlike coffee, however, we can get a better result by running the same water through twice. For a stronger solution this is a good idea.
Unlike making a lye solution from solid lye, you cannot predict ahead of time how strong your solution is. So how do you know whether it is strong enough, and what can you do to change the strength? First, it depends on what you want to use the lye solution for. In soap making there are a couple of rules of thumb to go by. First, a fresh egg should float in the solution with an area equal to about a nickel to a quarter (2 to 2.5 cm). Bear in mind that most eggs from stores are at least a month old, and will float higher in water than a truly fresh egg. Also bear in mind that you should not eat the egg after the test. The second test involves a chicken feather (probably any fowl will do), which should start dissolving in the solution if it is ready.
If the solution is not strong enough, you have two choices: first, you can run the solution through ashes one more time, or you can boil the solution to evaporate some of the water. The second option is tricky, as lye will react to most metals, possibly damaging the pot, releasing toxic fumes, and preventing the strengthening of the solution. If the solution is too strong, simply add fresh rain water to weaken it.
So what is lye solution used for? I have already mentioned soap making, as well as street drugs, but it also comes in handy in making bio-diesel fuel, various cleaning products, and certain food product preparations. Olives, lutefisk and pretzels are just a few of the food products that are "cured" in a lye solution at one stage or another. I do NOT recommend trying food preparation with lye at home, as there is a very great danger involved in not removing all the lye from the food before the end product is finished.
If you want to try your hand at making your own lye solution, go to Journey to Forever for some set-up diagrams for simple processes, and the End Times Report for a description of how to make an "automatic" lye production system.