Lye has many important uses known well to soap-makers and also to plumbers for its corrosive properties in clearing clogged drain pipes. However counter-intuitive it might seem at first lye has an essential part in the production of food products like pretzels and bagels, creating their infamous color, texture, and flavor.
Lye is sodium hydroxide (NaOH). This now an industrially-processed product that was traditionally made from just the ash from burnt hardwoods. It’s been widely available, and quite easy to make. The ash was left in water to soak (preferably soft with rain as a natural option) and as the ash settles on the bottom the sodium hydroxide-laced water could be scooped off the top. This can be achieved through boiling for a quick turnover, or for a more passive method, filling a bucket with drain holes on the bottom and leaving it outside with a container beneath to catch the lye water that runs off as it rains.
As a result of the ash infusion the water becomes alkaline, in some cases maxing out at a pH of 14. At this point touching it with your bare skin can cause chemical burns and ingesting can be deadly. That’s why it is best when working with lye to wear a good pair of rubber gloves. To be certain, the dangers are real and caution should be used in handling, and definitely don’t ingest straight lye, however while being baked in the oven lye’s harmful properties are neutralized and become deliciously edible.
When looking for a store-bought food-safe lye it can be a little tricky. However the soap-makers can help you here. With a little research they can point you to companies that sell 100% pure lye which is what you’re looking for. It’s the additions that can be the problem with food safety. The product pictured below is what I use for pretzels and bagels. Keep in mind that in granular form it is quite concentrated and needs diluted significantly.
Making Lye from Ash
For homemade lye using ash, while it will never be as precise, comes with the comfort of being produced entirely from nature and your own resources. The ratio I use is soaking two cups of ash in a quart of water. A descent way of testing it is to place an egg in it and see if it floats. Usually about two days at room temperature does the trick, but keep in mind the results have many variables.
What does Lye do?
We know pretzels because of their unique pretzel flavor and appearance. The difference between a pretzel and regular bread is the added influence of lye. When bread is baked the outer parts are caramelized to form the crust. This caramelization is the result of the Malliard Reaction which is a heat-activated reaction between small sugars and amino acids (protein) which alters characteristics of flavor, texture, and appearance (browning). With the introduction of lye the ratio of that relationship is changed by sodium hydroxide breaking down the proteins into smaller pieces which results in the distinct characteristics of pretzels.
The application of lye to a pretzel is often a simple dip. A concentrated lye water serves as a bath for the shaped and proofed knots before entering the oven. In some cases the lye solution is brushed on, however be thoughtful of what kind of brush your using as the lye does have the capability of dissolving certain synthetic bristles. (Learned that one from experience.)
For making pretzels the Perfect Loaf has a solid formula that should serve as an excellent launching point.
Bagels have an interesting relationship with pretzels. In Maria Balinksa’s book The Bagel: The Surprising History of a Modest Bread, she makes the connection between the earliest pretzels being ringed shaped (possibly relating to heavenly connotations), and the process of making a bagel that came soon after. So in the case of bagels, imagine a ringed pretzel situation but that are boiled in a lighter lye bath, then baked.
For making bagels as with any recipe it is up to your preference. Typically I’ll add either a cup of ash-made lye water to 2 quarts of boiling water or a teaspoon of granulated lye. It is also possible to use baking soda which provides the element of alkalinity, albeit in lesser but no less useful concentrations since we’re not going for full-on pretzel when making a bagel.