Was Vinegar Used for Megalithic Stone Softening?

Was Vinegar or perhaps Selenium Acid used Stone Softening for Egyptian & Peruvian Megaliths? Two new possible acids for your stone softening consideration.

In this post, I present two new possible sources of acids that could have been used to soften limestone and granite enough to be worked with bronze age, or perhaps even copper tools in Egypt and Peru. Both could have been easily discovered by accident as well.

The first is Selenous Acid, made from a copper smelting byproduct, soda ash and limestone.

And the second is…the common household vinegar. Yup, I said it. Vinegar. And a quick Google search doesn’t reveal any major articles discussing its potential. If it was used, it seems like the kind of common knowledge that could have easily been lost as harder metals came on the scene and made the technology obsolete, and vinegar simply went back into use for other things.

Before we get into the chemistry, I want to discuss a major point of contention I have with the current understanding of ancient times. I personally think there was a bit more iron metal floating around in ancient times that had been hunted and collected and reshaped from meteoric iron. Putting the iron question aside, let’s just focus on the copper vs bronze debate.

COPPER vs BRONZE tool timeline

An alloy of copper with arsenic or tin is what makes bronze.

I believe it is a common misconception that the ancient megalithic builders of Egypt used only copper tools. Both the Sinai mines and copper mines of Peru are naturally high in arsenic, which means it was very hard copper, and they only needed a little tin to harden it into bronze.

The debate between copper and bronze tools is important, not only due the hardness of bronze over copper, but also because bronze doesn’t oxidize or corrode as easily when exposed to liquid or acid, as does copper. The fact that archeologists only find copper tools from that period probably only indicates that the higher quality bronze tools were prized, reused, and carried off, while copper tools were not, or may have even been ceremonial in nature.

There is some archeological evidence that the Egyptians first produced bronze in 4,000 B.C, although it is accepted that it did not become common until the New Kingdom, after 1500 B.C. If the Egyptians did produce bronze as far back as 4000 B.C., it would point to an extensive trade network extending to either northern Europe, or at the very least, the precursors to the Etruscans in Italy, the closest source of tin.

It is currently believed that the Maykop culture of the Caucus Mountain region (c. 3700 BC to 3000 BC), is the most likely candidate for the origin of Bronze production. Archeologist believe that it only reached Mesopotamia by 3000 B.C. Such linear timelines are archaic, and fundamentally disregard catastrophe cycles that collapse previous civilizations. After a collapse, everything is salvaged for the next kingdom. During this time, metal would have been the number one salvage item.


A smelting process for bronze that mixes in arsenic would have produced poisonous fumes, and thus probably occurred away from population centers, but near a source of water.  

The Egyptians mined copper from Sinai and smelted it there. This copper contained naturally high amounts arsenic.  This made it particularly hard, and suitable to hard copper, or bronze by adding tin.

The Sinai is surrounded by salt water with very few trees for fire building or water to cool finished products. It’s quite likely the smelting was done closer to the Sea to obtain supplies of both.

Bronze is also far less prone to rust than copper. This is important to note if we believe that ancient megalithic builders used an acid in conjunction with copper.

The reason is that acids are actually used to clean and shine bronze, and vinegar is still commonly used.

The idea of vinegar as an acid source for stone softening occurred to me while I was researching another quite plausible acid source formed from the byproducts of copper smelting.

Or, so I thought, before considering vinegar.

It seemed natural that a copper smelting byproduct’s other uses might be discovered by accident, since that is often that nature of scientific progress. However, I must say, I am quite surprised that no-one has considered or proposed vinegar as a stone solvent yet. It seems even more plausible to me than the copper byproduct, and it is far less toxic, although I have yet to test this idea.

Recent findings point to vinegar being a widely available acid as far back 5000 BC, in Babylonian, and likely Egypt. This common household product (to us) was a revolutionary technology back then, with many uses including food preservation. Like many new technologies, its uses may have been more widely explored back then, much more than we may imagine. It was a product involved with early food and alcohol preservation, and still has many uses.

And most pointedly, vinegar is simply made from fermenting fruits, yeast and sugar. It is so ubiquitous a “technology” now that it is considered common knowledge rather than a curiosity. However, once vinegar was discovered, its many uses would have become apparent fairly quickly.

Certainly, vinegar spilled on a stone or stored in a limestone bowl would demonstrate to any casual observer that it weakened the stone, (due to its corrosive pH). Perhaps it allowed it allowed a valuable stone bowl to weaken and to chip.

Ergo, people could have quite easily realized it was able to soften limestone and granite enough to be chipped away by bronze or copper tools.

Speaking of copper, let’s explore the potential discovery of Selenous Acid adjacent to copper smelting communities. It is an interesting idea, worth exploring as much as Helmut Tributsch’s pyrite mud hypothesis as a source of acid, or Lia Mangolini’s hypothesis the ancient megalithic builders may have used Hydrofluoric Acid, obtained from certain plants.


During the purification of copper, one of the byproducts in the reside is Selenium dioxide.

This residue can be oxidized with sodium carbonate, or soda ash, to produce selenium dioxide, which, when mixed with water & acidified forms selenous acid. 

Seleneous acid is analogous to Sulfuric Acid.

So, copper smelting slurry + soda ash + water = an acid that dissolves limestone and granite.

Selenate and other forms of selenium are highest in areas where ancient seas have evaporated, and historically, soda ash was extracted from the ashes of plants growing in sodium-rich soils. 

This means these two ash byproducts were highly likely to come in contact with each other and with water at some point, making the phenomena of dissolving rocks easily discoverable.

Another means to obtain Soda Ash, or Sodium Carbonate, is called the Solvay Process, named for the Belgian Chemist Ernest Solvay who discovered it in the 1860s. This process only uses sea water and limestone.

In other words, Selenous Acid could potentially be formed by simply placing copper slurry + sea water on limestone. That is also a seemingly easy accidental discovery.

If we consider that the residue from copper smelting was likely considered a waste product, as may have been burnt sodium rich plant material such as ocean delta grown crops, then its quite feasible these two waste materials simply discarded in a trash heap together with some limestone trash rocks, or haphazardly on some limestone. A rainfall could add the necessary water to demonstrate to onlookers that the rocks were melting.

This is an oversimplification but I am simply spitballing ideas for consideration here.

Furthermore, another use for selenous acid is the chemical darkening and patination of copper, brass and bronze, producing a rich dark brown color that can be further enhanced with mechanical abrasion to prevent weathering, hence, this is something quite likely to have been of interest to early metallurgists.


Limestone dissolved by acid forms a salt (in the chemical sense), water, and carbon dioxide, so if something like vinegar was used, no trances would remain. Many more clues would likely remain if Selenous Acid was used, and this idea can easily be proven or disproven by further investigation or direct evidence.

Vinegar, on the other hand, would not.


I find it interesting that in order to make vinegar, one need steady warmth (70-80 degrees is ideal), darkness and good air circulation, which sounds much like the interior of the Pyramids and other megalithic structures. It makes me realize how important temperature is in conducting accurate chemical experiments and extractions, and how those technologies represented power in the ancient world, as did the knowledge of smelting.

According to ancient scrolls, vinegar was known to Babylonians 5000 years ago. Such a technology would not have remain hidden for long. It was undoubtedly known to the Egyptians around this time as well due to its excellent food preserving and disinfecting abilities. Egyptian urns with traces of 3000 year old vinegar have been found.


The toxicity depends on the chemical form of selenium. It is unlikely the ancient smelters would have produced a highly concentrated or purified form.

Selenate is its least pure and least toxic form.

Human toxicity from environmental exposure to elemental selenium and selenium salts is rare, however, exposure to a highly concentrated selenous acid or to selenium dioxide can cause serious toxicity.

Target organs include: respiratory tract, CNS, cardiovascular system, gastrointestinal tract, skin.

The ingestion of any significant quantity of selenous acid is usually fatal, however it is an approved dietary source in proper amounts.

After skin exposure to 50 % solution of selenous acid, signs develop within several hours: unremitting intense pain, red and swollen skin, blisters, which may be followed by ulcerations.

Chronic exposure to selenium manifests as brittle nails and hair, pruritic skin rash; longitudinal streaks or transverse lines may appear on the surface of the nail in the form of yellowish-white or red discoloration (Barceloux, 1999).

Ingestion of selenous acid causes corrosive injury to the gastrointestinal tract, stupor, respiratory depression and refractory hypotension and ARDS.

Therefore, in order for a Selenium based acid to have been used, it would have needed to be a very highly diluted liquid or a low concentration paste.

In weighing these two possibilities, I think vinegar makes more sense than anything I have seen proposed previously regarding stone softening. Notwithstanding a discovery of copper or selenium residue on stones, and considering the extremely negative health effects from using Selenous Acid, following Occam’s Razor, I personally lean towards the Vinegar hypothesis of stone softening.

I will try to test the vinegar hypothesis this spring and bring you the results.

Until then, let me know what you think of these ideas.

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