Pique the Geek 20111211: Would I Lye To You?

(9 pm. – promoted by ek hornbeck)

Sodium hydroxide, aka lye, is one of the most important basic chemicals used in industry, and until not too long ago, for several home uses.  It can still be found in a few consumer products, but because of its usefulness as a chemical reagent for clandestine preparation of methamphetamine, is hard to get now without a legitimate business reason.  However, I found some at Lowe’s a couple of years ago (under a different label) for opening drains.  I wanted some to show my relatives how to make soap.

A significant amount of this material is still used for making soap, but its uses are so widespread and pervasive that soapmaking is just a small fraction of the applications for this material.  Industrially it is used when a strong, cheap base is needed, because it is amongst the strongest and cheapest, other than perhaps calcium hydroxide (lime), but sodium hydroxide is very soluble in water where calcium hydroxide is not.

The formula for sodium hydroxide is NaOH, giving it a formula weight of 40 grams per mole.  It is indispensable in the chemical laboratory, being used for everything from a glassware cleaner to an important reagent for many chemical reactions.  Sometimes the more expensive potassium hydroxide is used instead because it is more soluble in alcohols than the sodium one.

In graduate school I had to do quite a bit of organic synthesis and used a base bath for cleaning difficult glassware.  A base bath is a big glass jar (the one I used was was about 20 L, or five gallons) filled with either ethanol or isopropanol with a lot of potassium hydroxide dissolved in it.  To use it, you just prerinse the glassware and then soak it overnight in the base bath.  The next day, glassware rinses clean with no scrubbing.  I also used a detergent bath for less heavily soiled glassware, which was just a similar container filled with distilled water and Alconox, a common laboratory detergent.  I ran a steam coil around the bottom of it since cold detergent does not clean well.  The advantage over the base bath is that even borosilicate glass is slowly attacked by strong base, so the gentler treatment was preferable.  However, the base bath still got a lot of use, particularly when removing stopcock grease from ground glass joints.

Sodium hydroxide is an extremely hazardous material to handle, and you need to know what you are doing when you do handle it.  Rubber gloves are important, and good eye protection is essential.  When you get sodium hydroxide on your fingers, it feels soapy.  There is a reason for that:  they ARE soapy!  The base is actually making soap out of the lipids (fats) in your skin.  Likewise, if it gets in your eye, it saponifies the lipids in your cornea, usually so fast that the cornea is badly scarred or destroyed.  ALWAYS wear eye protection when handling this material, no exceptions.

These days, sodium hydroxide is manufactured by the chloralkali process, where a concentrated solution of sodium chloride, common salt, is is subjected to a heavy direct electric current.  The overall reaction produces sodium hydroxide, chlorine, and hydrogen.  It is energy intensive, but since all three products can be sold, it is profitable.

Obviously, it not feasible to conduct such a process in a home setting, but there is an older one that is easy to do.  We shall get back to that later after we discuss why anyone would need to have lye at home, and there are several.

Scores of millions of tons of sodium hydroxide are produced annually, and much of that is used in the paper industry.  It is used with sodium sulfide to separate the cellulose fibers from the lignin “glue” that holds them to make wood.  About 25% of total domestic production is used in this manner.

Lots of it is also used in the soapmaking industry, since it is the cheapest strong base that is water soluble.  Some specialty soaps use potassium hydroxide instead, and these tend to be liquid while sodium soaps are solid.  Most pump hand “soaps” are really not soaps at all, but rather synthetic detergents blended with water.  You can tell what is used to make the soap by looking at the label.  My bar of Irish Spring indicates that the soap is either sodium tallowate (as in tallow from beef fat), sodium cocoate (from coconut oil), or sodium palm kernelate (from palm kernal oil).  The reason that these fats are used is that they are the cheapest available, and are highly saturated, making them less desirable for food purposes than some of the other fats.

There are many more industrial uses for lye, but let us cover some of the home uses.  Most drain cleaners use lye as the primary active ingredient.  The liquid ones also contain thickening agents to slow their transit time, thus giving greater contact with the clog.  They work by saponifying the fats component of the clog, and also by degrading other materials like hair of food waste.  Sodium hydroxide is extremely caustic to many things, so it is a good choice for a drain cleaner.  The solid form of Draino also contains aluminum turnings.  Sodium hydroxide itself releases a lot of heat when dissolved in water, and the addition of the aluminum increases the heat released, thus melting as well as saponifying the grease.  This reaction also releases a significant amount of hydrogen gas, so keep that in mind.  Sodium hydroxide reacts very vigorously with aluminum, so never use aluminum containers or utensils when working with it.  Stainless steel, glass, and plastic are fine, but beware of the potential for melting a plastic vessel when dissolving it because of the heat that it releases.

Another household use for sodium hydroxide is as an oven cleaner.  I use it for cleaning the racks, because the high temperatures involved with the self clean cycle damages the finish.  You can buy it in a spray can at any grocery or hardware store.  Back in the day before self cleaning ovens, it was the norm to heat the oven to warm, then spray the cleaner on the soiled places.  Then you let it sit overnight, and wiped the mess out with a warm, wet washcloth whilst wearing rubber gloves.  I remember my mum doing that many times.

Do not use oven cleaner on self cleaning ovens.  The lining has a catalyst in it to help turn the drips to char, and oven cleaners can interfere with with them.  Using it on the racks is fine.  You may be tempted to use it to clean baked on messes from cookie sheets and other utensils that go in the oven, but read up on your cookie sheets first.  Some have a finish for even cooking that can be damaged.  Once again, never use it on aluminum or you will be throwing your sheet away.

There is an alternative to lye based oven cleaners.  Those contain usually potassium carbonate (a much milder base) and ethanolamine.  They take longer to do the job, but you can use them on aluminum objects without eating them away.  You can also use those kinds of products on self cleaning ovens if the clean cycle did not completely get the burnt on food.

Sodium hydroxide is used in many consumer products for pH control.  Since it is not toxic, it can be included in things that are injected or in things like eye drops.  Now, please do not get me wrong:  there is a difference between nontoxic and corrosive.  Neither sodium ion nor hydroxide ion are poison, but concentrated solutions of sodium hydroxide are deadly if ingested because of its corrosive effect.  It is all a matter of concentration.

Since it is not toxic, it has several food uses.  Pretzels have the crust that they do because they are soaked in a dilute lye solution, then rinsed, salted, and baked.  The lye treatment produces a darker crust and the unique flavor.  Another use is in treating grain to improve some of its properties.

This process, called nixtamalization, involves partially cooking corn (usually) in a lye solution for a fairly short period of time, then allowing it to soak until the pericarp (hull) is loosened.  The pericarps are removed, by hand in small operations or by machinery in industrial settings.  The grain that is left in now either cooked to be eaten whole as hominy, cooked and dried, then ground to make hominy grits (many modern grits are just made from corn that has not been treated with alkali), or ground finely to make masa harina.  Corn Nuts are nixtamalized large grains of corn that are subsequently fried and salted.

The process has benefits in addition to changing the flavor.  It turns out that treating the corn with lye releases niacin, making grain so treated more nourishing than if left untreated.  It also changes the properties of the starch so that it sticks together better, so tortillas hold their form rather than fall apart.  That is a good thing, since corn does not contain gluten.  Calcium hydroxide is often used instead of lye since high concentrations are not needed, so the low solubility of calcium hydroxide is not a problem.

Another use for lye is making lutefisk, popular in parts of the US with large Scandinavian populations.  It is made by hydrating dried whitefish, then soaking it in lyewater, then rinsing the lye out of the fish over several days, then cooking the flesh.  Since dried fish is the basis for the dish, it was used to preserve fish that otherwise would have spoilt before it could otherwise be eaten.

Around the house I use lye to clean tough stains from things like ceramic coffee and tea mugs.  I told you that it is easy to make, and it is, using common household materials.  The two ingredients are either baking soda or washing soda and pickling lime.

If you are using baking soda, you have to heat treat it in the oven at about 400 degrees for an hour or so.  This drives out water and carbon dioxide to form sodium carbonate.  If you are starting with washing soda, which IS sodium carbonate, you need to heat treat it for around half an hour at the same temperature to drive off any water of crystallization, so you can weigh it accurately.  For general purpose cleaning, around a 10% solution in water is fine, but mind my cautions about eye protection and rubber gloves, because 10% is caustic enough to hurt you badly.

To make a quart of this solution, take 133 grams (4.7 ounces) of the sodium carbonate and dissolve it in water in a quart glass Mason jar.  Then add 92.5 g (3.3 ounces) of the pickling lime to the jar.  Be sure not to fill the jar up completely with water when dissolving the carbonate because the lime is really fluffy.  A postage scale is ideal for weighing out these amounts.  Do not worry if you are a little off on them.  Even though the lime is only slightly soluble in water, it is soluble enough that the reaction proceeds.  The two products are sodium hydroxide (you end up with 100 grams of it) and calcium carbonate (you get 125 grams of that).

The overall reaction is:

Na2CO3 + Ca(OH)2  yields 2NaOH + CaCO3

Do not worry if nothing seems to happen.  The calcium carbonate (chalk) is almost completely insoluble in water but it looks just like the lime that you added.  Put a lid on the jar and shake it, then loosen the lid because there will be some temperature rise.  Let it go a couple of hours, tightening the lid and shaking the jar every now and then, then loosening the lid to vent any pressure buildup.  After a couple of hours, let the chalk settle to the bottom and carefully pour off the sodium hydroxide solution, taking care to wear rubber gloves and eye protection.  Put a cup of vinegar in the jar with the chalk to neutralize the sodium hydroxide coated chalk, and then you can safely dispose of it.  I do not recommend putting it down the drain, since sodium hydroxide will not dissolve chalk, and neither will water, so it is better to pour off the vinegar and put the chalk in the trash, unless you want to keep it for an antacid.

Addition:  the liquid that you pour off of the chalk needs to be diluted with water to make a quart.  Just add cold tap water to it until it comes to the top of a new quart jar.  If you do not adjust it, the concentration will be over 10%.

If you want to make hominy or pretzels with this, I recommend using baking soda as the starting material, since it is food grade.  Washing soda is not food grade, but it is fine if you just want a cleaning solution.  To use the solution for food purposes, you need to be accurate with your measurements making it, and use the proper dilution for the recipe at hand.  There are lots of recipes on the Tubes.

This actually was the commercial manufacturing process for lye for years, of course on a larger scale, until the chloralkali process was developed.  No sodium hydroxide is made this way on a commercial scale any more.  You actually can make much more concentrated solutions, using this scheme because sodium hydroxide is extremely soluble in water, but I recommend that you hold it to a 10% concentration because as concentration increases the hazards do as well.

When you are done with the lye solution, just pour it down that slow drain and it might help to unclog it.  Sewerage systems handle lye easily, and it is not harmful to pipes at this concentration.  By the way, NEVER use drain cleaners of any type to try to unclog a toilet, because of their construction.  The drain cleaner never reaches the clog in amounts that would help, and then you have a toilet full of caustic solution, making it hazardous for the plumber to do her or his job unclogging it.

I should mention one other large scale use for sodium hydroxide, and I am not giving away any classified information saying this.  At the chemical weapons stockpile at Bluegrass Army Depot, concentrated solutions of it are going to be used to destroy the two nerve agents stored there.  That is common knowledge here, but not known to many out of the region.

Well, you have done it again!  You have wasted many einsteins of perfectly good photons reading this caustic piece.  And even though Rick Santorum realizes that he has no chance at the nomination when he reads me say it, I always learn much more than I could possibly hope to teach when I write this series.  Thus, please keep those comments, questions, corrections, and other feedback coming.  The community was very nice to me Friday evening when I was going through my emotional crisis, and I appreciate it.  I shall hang around as long as comments warrant, and I shall return tomorrow at about the same time for Review Time.

Warmest regards,

Doc, aka Dr. David W. Smith

Crossposted at

The Stars Hollow Gazette,

Daily Kos, and



  1. me holding on today?

    Warmest regards,


  2. I very much appreciate it.

    Warmest regards,


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