The article “Photoformation of low-molecular-weight organic acids from brown water dissolved organic matter” by Brinkmann T1, Hörsch P, Sartorius D, Frimmel FH we read:
“This work describes the effects of simulated solar UV light on the bulk properties of dissolved organic matter (DOM) of bog lake water and on the formation of low-molecular-weight organic acids (LMWOAs). By means of size-exclusion chromatography it was shown that the more hydrophilic moieties of the DOM were preferentially photodegraded while the more hydrophobic ones remained relatively unaffected or were even formed. The combined photochemical-biological degradation proved to be more important than the pure photochemical mineralization. Formic, acetic, pyruvic, oxalic, malonic, and succinic acids were identified as important degradation products. Their contribution to the dissolved organic carbon increased from 0.31% before to 6.4% after 24 h irradiation. About 33% of the bioavailable photoproducts of DOM were comprised of these LMWOAs.“
Translated into plain English, solar radiation will degrade organic matter found in bog water and form more low-molecular-weight organic acids (LMWOAs), making the bog water even more acidic. How much more acidic? Not sure what the final pH of the bog water exposed to the sunshine is. But it is definitely low enough to serve as a very good pickling solution.
Pickling is the process of preserving or expanding the lifespan of food by immersing in pickling brine (salty and acidic liquid). If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt which draws water out of the food creating salty liquid. Natural fermentation at room temperature, by lactic acid bacteria, produces the required acidity creating salty and acidic liquid – pickling brine. If the food does not contain sufficient moisture, pickling can also be achieved by immersion of food in some salty acidic liquid, such as mixture of salty water and vinegar. If you want your pickling to be successful, the pH of the pickling brine has to be 4.6 or lower, which is sufficient to kill most bacteria. The pickling procedure will typically affect both food’s texture and flavor but it will preserve otherwise easily perishable food for months or longer. Foods that can be pickled include meats, fruits, eggs, vegetables and milk products like cheese.
Now bog water has a pH of 3-4 before solar irradiation. Well below the required acidity of pickling solutions. For those who don’t know much about pH scale, here is a quick overview. The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic and more than 7 is caustic. The scale is not linear but logarithmic. This means that liquid with pH 3 is 10 time more acidic than the liquid with pH 4…
So bog water is 10 time more acidic than what is at minimum required from a pickling solution in order to kill all the harmful bacteria in the food.
Yes but what does pickling has to do with bog water? Who would use bog water for pickling? Well as it turns out a lot of people. And some of them could have been the Bronze Age Irish builders of fulachta fiadh
As I already said in my post “Fulacht fiadh – meat and fish curing facility”, the ancient Irish probably used both salt and smoke curing of meat and fish as a means of preserving it long term. But there is another way Ancient Irish could have preserved food long term without need for salting or smoking.
“Fill your other trash can with clear, lukewarm water. After the soaking is complete. Use the stirring stick to carefully move the skins one by one into the trash can with clear warer. This is the rinsing process, which removes the excess salt from the skins. Stir and slosh the skins for about five minutes, changing the water when it looks dirty.”
Take the skins out of the fulacht fiadh trough. Take them to the stream and wash them thoroughly until the water coming out of them is clear.
If you decide to use baking soda, place the hide in the neutralizing solution, and stir for 20 minutes. Remove the hide from the neutralizing solution, rinse, and drain.”
If you want to wear the skins you are treating or use them as bed covers, you should probably neutralize the acid in them. This is how to do it. You can’t use fulacht fiadh trough for this, as it will fill with acidic bog water as soon as you empty it. You will have to use either large pots, like large funerary pots, or you will have to take the skins to another fulacht fiadh which is built in a dry well drained soil and use the trough there, Whatever you decide to do, you will need to use something in place of baking soda, as it was not readily available in Bronze Age Ireland. Baking soda is Alkali. In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal chemical element. An alkali also can be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. Now when you mix acid (pH < 1) and alkali (pH > 7) you get salts and neutral pH. So where do we find an alkali that can be used instead of baking soda, and that we can use to neutralize acid in the skins we have just pickled?
The word “alkali” is derived from Arabic “al qalīy” (or alkali), meaning the wood ashes, referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly of potassium carbonate, is mildly basic. After heating this substance with calcium hydroxide (slaked lime), a far more strongly basic substance known as caustic potash (potassium hydroxide) can be produced. But for de-acidifying our skins, we need ordinary weak base – potash. So grab few handfuls of wood ash from your fireplace and chuck it into the pot or fulacht fiadh trough full of clear water. How much will depend on volume of your vessel. For a 150 liters trough you will need 1 kilo of ash. The major components of wood ashes are potassium carbonate (potash) and sodium carbonate (soda ash), and their average pH is about 9,5 while the pH of baking soda is 9. Mix the solution. Submerge your skins in and leave them soaking for not more than 20 minutes. If you leave your skins in the potash solution for too long, the hair will start slipping (falling off), which is exactly what potash is used for in bucking, as I already described in my post “Fulacht fiadh – tannery”.
“Remove the hide from the rinse and hang over a beam to drain. Rub it with some oil, like neatsfoot oil, salmon oil, beechnut oil, to condition the skin.“
Hmmm. I am not sure what kind of oils Bronze Age Irish had access to. Probably salmon oil and beechnut oil. So, get the skins out of the potash soulution, squeeze them and then leave them over a branch to drain. Get some oil and rub it into the skins.
“Stretch the hides on a stretcher or hide dryer to finish the process. Place it in a place out of the sun to dry. After a few days the hide should feel dry and flexible. Take it down from the rack and go over the skin side with a wire brush until it has a suede-like appearance. Let the hide finish drying until it is fully dry, which should take a few more days.“
A bog body is a human cadaver that has been naturally mummified in a peat bog. Unlike most ancient human remains, bog bodies have retained their skin and internal organs due to the unusual conditions of the surrounding area. These conditions include highly acidic water, low temperature, and a lack of oxygen, and combine to preserve but severely tan their skin. While the skin is well-preserved, the bones are generally not, due to the acid in the peat having dissolved the calcium phosphate of bone.
The oldest fleshed bog body is that of the so called “Cashel Man“, who dates to 2000 BCE during the Bronze Age.
The best preserved bog bodies in Ireland are:
Clonycavan Man, an iron age bog body dated to 392-201 BC
Oldcroghan Man, an iron age bogman dated to 362-175 BC
The best preserved fleshed bog body is that of the so called “Tollund Man“. Tollund Man is a naturally mummified corpse of a man who lived during the 4th century BC.
Now some people will say: “Well these are preserved because they have been kept inside the bogs in anaerobic acidic conditions for thousands of years…The conversion of skin to leather took a long time….This was not a practical procedure which could be used for tanning animal skins…”
Well I am not surprised that you might say that. I had the same doubts myself. But then I came across this.