Using Lye Safely in Soap Making, by LadyDoc

Soap is arguably one of the greatest inventions, ever.  Most people do not need to be convinced of the advantages of soap, especially in terms of preventing infections.  Using soap for personal and property cleaning when medical care and antibiotics are not readily available will be a vital part of avoiding contagious diseases.  Elegant in its simplicity, soap is made from two ingredients, lye and fat, through a chemical process called saponification.  This process cannot occur without both ingredients in the proper proportion.  Making soap for household use post-TEOTWAWKI raises some challenges, two in particular that I believe warrant the most consideration:  first, using fats that are needed as a calorie source to make soap and second, storing lye for soap-making.  Lye is a dangerous chemical, with several pitfalls that make the possibility of injury high, particularly for someone who is unaware or indifferent to the safety issues involved. 

Before purchasing a bottle or two of lye and tucking it back on the shelves to store for a time when making soap seems a good idea you should have an understanding of the risks of handling lye and the treatment of injuries that will occur if lye is not handled with extreme caution.  Injuries from lye can be thermal or chemical burns or both.   Lye is a strong base that will react with many substances, taking the hydrogen ions (H+) from those substances to react with the hydroxyl ion (OH -) in sodium hydroxide (NaOH) or potassium hydroxide (KOH), either of which is called lye.  This chemical reaction is exothermic, producing a large amount of heat.  The heat generated can be enough to cause a small explosion in the presence of combustibles.  Lye has a pH of 13.5 for KOH and 14 for NaOH when in a 5% aqueous solution (for comparison, common white vinegar is an acidic solution of about 5% concentration).  In the measurement of acid and base strengths, a pH of 14 is the strongest base possible. 

When in contact with skin, mucous membranes such as the nose, mouth and airways or with eyes, lye will react immediately to create a potentially severe chemical burn in addition to the thermal burn from the exothermic reaction.  This burning will continue for at least several minutes after exposure until first aid is administered which is essentially diluting the base as quickly as possible.  Copious washing must be performed; up to sixty minutes of uninterrupted irrigation for the skin and for the eyes, depending on the amount of lye the person is exposed to.  Unless the water is grossly dirty or contaminated with raw sewage you may use plain water to perform the irrigation, in large quantities and do not worry about using only sterile water or saline if none is immediately available.  The key is to dilute the lye as quickly as possible.  Do not attempt to neutralize the base by adding an acid (such as vinegar or lemon juice) to the skin or eyes since this will release more heat and worsen thermal burns that have occurred in addition to the chemical burns.

The long term consequences of lye burns can be severe.  Permanent scarring of the skin and subcutaneous tissues is common following a lye burn.  Blindness is easily a consequence of lye burns to the eyes due to corneal scarring and clouding.  Irritation of the airway can cause pulmonary edema (or swelling of the lung tissue and fluid accumulation in the lungs) which can take up to 48 hours after exposure to occur and can be fatal. 

Lye must be stored in a tightly sealed container to avoid chemical reaction with carbon dioxide (CO2) in the air which will make the lye into sodium carbonate, which is not effective in the saponification of fats to make soap.   A tightly sealed container is also necessary to prevent the absorption of water from the atmosphere.  Lye can absorb enough water from the atmosphere to make a slurry or solution which makes measuring and using the lye difficult.  Desiccant packs are not effective in preventing lye from absorbing water because the lye absorbs water better than the desiccant pack and so will actually absorb water from the desiccant pack. 

When dissolving lye for use extreme caution must be taken.  Contact with water causes a violent, almost explosive, reaction and lye can be easily splashed at this time, causing burns to skin, eyes and mucous membranes unless appropriate protective gear is in use.  Always use eye protection and heavy rubber aprons and gloves when mixing and using lye.  Clean these items after use by copious washing where the run-off will not be able to be contacted by children or animals. 

Contact of lye with metals, especially aluminum, magnesium, zinc, tin, chromium, brass and bronze will create hydrogen, a highly explosive gas.  Care must be taken to avoid contact with these metals and lye needs to be kept in appropriate containers and never moved to a container for storage not originally intended for lye storage.  Once the container is emptied, (again) care must be taken when discarding the container to avoid contact with skin or chemical reactions. 

If all of this isn’t enough to scare you off storing lye without the appropriate cautions please consider some of the other factors in making soap.  A calculation of the cost of producing hand-made soap suggests that it may be more economical to store soap rather than lye.  (Certainly it will be safer.)

Most recipes for soap specify approximately 10 parts of fat for each part of lye, although this is extremely variable based on the type of fat being used.  To produce soap post-TEOTWAWKI will require a relatively large amount of fat, a precious resource.  As many authors on this blog have pointed out, fat will be one of the most difficult food categories to provide for our families, yet is incredibly important.  This seems strange in today’s society where fat is ubiquitous and almost no one goes without enough fat in their diet.    Without fat however, fat soluble vitamins (A, D, E and K) are not absorbed from the diet and deficiencies can occur.  Fats are also an efficient source of calories, providing 9 Calories/gram, compared to 4 Calories/gram for protein, carbohydrates and alcohol.  For most people, using fat to make soap will be taking an important food item from their families when they need it the most. 

On a search of the Internet the least expensive price I could find for lye was $3.49 for a bottle of 32 ounces (2 pounds) or approximately $0.11 per ounce. The cost of making soap also needs to include the cost of the fat used in the process (which is often left out of the recommendation to store lye for the purpose of making soap at a later date).  Lye must react with a fat to produce soap.  The cost of fats varies widely but for argument’s sake consider olive oil at $4.06 for a 17 ounce bottle or $0.24 per ounce. 

Most recipes for soap that I have seen require about 1 ounce of lye and approximately 10 ounces of oil to make approx 11 ounces of soap.  Simple arithmetic tells us that $0.11 + $2.40/11 = about $0.23/oz for hand-made soap so a four ounce bar would cost about $0.92.  At the local big box discount store in the last month a 4 ounce bar of Ivory soap was $0.38 when bought in a pack of 10 bars.  Ivory soap can be used for washing clothing and dishes as well as bathing since it does not contain perfumes or coloring agents.  A year’s supply of soap can be purchased for under $20, depending on the size of your family.  In my humble opinion, after TEOTWAWKI, any fat that is stored or acquired/grown is better consumed as a calorie source and to ensure adequate fat-soluble vitamins for you and your family rather than being used as a source to make soap.

Recognizing that even the largest stash of soap won’t last forever, a reasonable alternative to storing NaOH or KOH is learning to make your own lye from wood ashes.  Recipes can be found on the Internet by searching for “how to make lye”.  You can make the amount of lye you need at the time you intend to use it without the risks of long-term storage.  This lye is still dangerous if not handled with care but since it is already in solution and dilute it is somewhat less dangerous than solid lye.  Once your supply of soap is exhausted, making lye in the amount that you need for the current use without storing it for future use seems to be a much safer option. 

I would suggest that it is false economy and dangerous to store lye for TEOTWAWKI in the anticipation of making soap.  If you really want to store lye to make your own soap please start now, gaining experience in handling lye when medical help will be much easier to access when an accident does occur.

Sodium Hydroxide Material Safety Data Sheet.  (9 September 2009). 

Potassium Hydroxide Material Safety Data Sheet.  (1 September 2009).