Potassium Bicarbonate

(also known as potassium hydrogen carbonate or potassium acid carbonate) is a colorless, odorless, slightly basic, salty substance. According to the US Food and Drug Administration (FDA), potassium bicarbonate is “generally recognized as safe“.  There is no evidence of human carcinogenicity, no adverse effects of overexposure, and an undetermined LD50. Physically, potassium bicarbonate occurs as a crystal or a soft white granular powder. Potassium bicarbonate is very rarely found in its natural form, the mineral called kalicinite.  The compound is used as a source of carbon dioxide for leavening in baking, extinguishing fire in dry chemical fire extinguishers, acting as a reagent, and a strong buffering agent in medications. It is used as an additive in winemaking and as a base in foods and to regulate pH. It is a common ingredient in club soda, where it is used to soften the effect of effervescence.  Potassium bicarbonate is often found added to bottled water to affect taste. Potassium bicarbonate has widespread use in crops, especially for neutralizing acidic soil.  But best of all….

Potassium bicarbonate is an effective fungicide against powdery mildew and apple scab, allowed for use in organic farming.

So make your own!!!  And we will.

Making lye from wood ash

Lye made from wood ash is potassium hydroxide, not sodium hydroxide — there’s 10 times as much potassium as sodium in wood ash.  The process makes lye water.  If you boiled off all the water you could use it as the catalyst to make biodiesel, but you’d need more accurate pH measures than those listed below.  The usual pH meter or litmus papers would do.

If you try this, we’d be very interested to know the results — please contact us.

Making the lye

Drill a lot of holes in the bottom of a small wooden barrel, make sure it’s waterproof before you drill the holes!  Stand the barrel on blocks leaving space beneath the barrel for a container. Use a waterproof wood or glass container. Lye can burn through some metals.  Put a layer of gravel in the bottom of the barrel over the holes, then put a layer of straw over the gravel. Fill the rest of the barrel with hardwood ash (NOTE: hardwood — NOT softwood), leaving a couple of inches at the top clear. Then pour rainwater into the barrel. After a long time the water in the barrel will start to drip into the container. Leave it until it stops, then replace the container with another in case of odd drips.  When the brown lye water stops coming out of the barrel, or ash container, then pour four to five pints (2-1/2 to three litre) of soft water through the ashes, collecting the lye which comes out in a separate “safe” container (as this lye may be weaker than the first lot).  Repeat this using two to three pints (one to two litres) of soft water, until no more brown liquid comes out of the ashes.  Either put the lye into “safe” bottles, or cover the “safe” containers which it is in. Dig the ashes into the vegetable garden.

Lye Water Strength, i.e. The Egg Test

Use an old iron pot, or a steel pan (One you will not be using for anything else!). Boil the liquid until it is so concentrated that a fresh egg (still in it’s shell please!) will float on top.

If an egg or potato will float just below halfway, or a chicken feather starts to dissolve in it, then the lye water is at the right strength.
If the egg will not float, then the lye water could be boiled down if you want it to be stronger.
If the egg seems to pop up too far, add a little bit of soft water (a cup at a time) stirring the lye water, until the egg floats so that its head pops up.

 Then destroy the egg. Remember to take all precautions not to let the liquid touch your skin or clothing.

To test the strength of the lye you need a saturated solution of salt. Dissolve chemical-free salt in a pint of water until no more salt will dissolve. Take a stick and put a small weight on the end of it and float it in a pint of the salty water. The weight will sink to the bottom, while the top of the stick will float. Make a mark on the stick where it reaches the water line. Then float the stick and weight in a pint of lye. The mark on the stick will probably be above the water mark of the lye. If so, stir in some more rainwater until the mark on the stick is in exactly the same place it was in the salt water. You now have the correct distillation of lye for making soap.  Leave to stand for four or more hours (or overnight if you have the time). Later pour the brownish lye water into a plastic or other “safe” container(s). Then pour back through the ashes again.  Repeat this using two to three pints (one to two litres) of soft water, until no more brown liquid comes out of the ashes.  Either put the lye into “safe” bottles, or cover the “safe” containers which it is in. Dig the ashes into the vegetable garden.



GRAS Notification Program (October 31, 2006). “Potassium bicarbonate”. GRAS Substances (SCOGS) Database. US FDA. Archived from the original on March 5, 2011. Retrieved March 5, 2011.


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