I'm designing a breed of cow that produces acid instead of milk. Part of the reason this is useful for my story is that the cows produce as much acid as a dairy cow would milk (through selective breeding/genetic modification.) Now, the dairy industry in 2013 produced 769 million tonnes of milk. Let's assume that the acid marked is half that (384.5 million tonnes). The dairy industry and a market has grown around this for a couple of reasons:


Research into the renewed possibility of an "alkahest."

And the criminal applications: if the acid was sold/stolen on the open market (or illegally) it would quickly become an agent for breaking through safes, etc (with the risk of damaging the internal components.) This would make the material resistant to the acid (see below) quickly become implemented as a security measure everywhere, which would create more and more ingenious ways of getting around that protection.

The acid is equal parts perchloric acid, aqua regia, and flouroantimonic acid. In other words, it's nasty stuff. A minute amount of unobtanium is used to keep them from neutralizing/oxidizing/destroying/whatever each other. The cow creates these from the special feed it is given.

According to this source, flouroantimonic acid, perchloric acid, and aqua regia (which has 2 components) are all held by PTFE (Which you might know as Teflon).


How could a cow protect itself using that material?

By which I mean these two points:

  • What would it need to eat (what would its diet be) to best synthesize the PTFE


  • What would the PTFE line; The parenchymal tissue? The udder cavity? Would it wear out over time?

Further clarification on what answers must include:

  • What changes to the diet of a regular cow, plus antimony supplements (for the acid) would need to be made to allow for the synthesis of the PTFE
  • Would there need to be an additional lining of cells to produce the PTFE
  • What organs/ducts/etc would the PTFE line

EDIT: You may use the acid to help you do whatever you need to do, such as mixing w/water for heat, using it to dissolve things, etc.

Please do not use magic as an answer. Handwavium is already being used for the nonreactivity of the acid; not for the protection of the udder tissue. That's why I came here to ask it instead of saying "it's magic." I've set a premise; please don't unbuild it. I'm using both the reality-check tag and the science-based tag because I want a reality-check with science. Try to work with the premise I've set instead of saying "it's unreasonable for the calf/cows don't produce acid milk/it's impossible for that to happen and the science-based tag shouldn't be used." I'm using the science-based tag in this setting because I want science-based answers to a problem set on an already built premise, which is set in stone. My reality-check is specifically about how it can protect itself, not about whether this is a reasonable premise or possible situation.

Thank you to all in the Sandbox for helping me develop this question, especially @Raditz_35 for all his expertise and guidance.

For those interested, there is a slang code built around this substance:

"Cheese": When the magic keeping the acids stable degrades and the acids form a useless substance.

"Cream": When the acid is separated into its components to selectively harvest only one acid from its components.

"Ice Cream": When the acids are cooled and pressurized for transport.

"Burnt Milk": When pressurized acid explodes.

"Yogurt": When a gel is made out of the acid.

"Skim Milk": When water is added to the acid, invariably causing dangerous, explosive reactions.

  • 5
    $\begingroup$ I just had the image of a cow used for a robbery, the robber milking (or "aciding") the cow directly to the vault $\endgroup$
    – Kepotx
    Jun 25, 2018 at 14:03
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    $\begingroup$ The problem being, these cows would produce such nasty stuff as to be biologically impossible to be contained inside their bodies. The vapors alone would escape the stomach and corrode the poor creature. I strongly suggest that they produce two kind of substances that, only when mixed up, give life to a potent acid. $\endgroup$ Jun 25, 2018 at 14:18
  • 4
    $\begingroup$ The biggest problem is that to make PTFE your cows must be over 550°C in order to undertake the necessary pyrolysis of chlorodifluoromethane to form the TFE monomers that go into making it. $\endgroup$
    – Ash
    Jun 25, 2018 at 14:28
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    $\begingroup$ If your cow is producing fluoroantimonic acid it is dead, there is nothing it can do to shield itself because even the glands producing it will be destroyed, fluoroantimonic acid is probably the most biologically destructive agent in existence. It also explodes when exposed to water, so making inside a living tissue is not going to work. Those acids are also not stable when mixed. you can't ask us not to unbuild a mixture that will explode as soon as it comes into existence. $\endgroup$
    – John
    Jun 25, 2018 at 16:05
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    $\begingroup$ @Ummdustry You may want to consider writing up an answer considering the level of knowledge you seem to have on the subject. $\endgroup$
    – James
    Jun 25, 2018 at 20:49

3 Answers 3


Okay, I’ll throw in my two cents to this question. First of all, this is not going to be a happy cow and I really hope that you don’t have a farm in real life. Honestly, there’s a reason that nobody’s even bothered to attempt biological PTFE synthesis, largely because of the amount of wince-inducing enzymes I’m going to have to use for the synthesis pathway. Sadly, this setup certainly fails the ‘reality-check’ tag.


Curiously, it’s possible to construct a pathway to PTFE of which the only real diet change would be the addition of fluorite. I’ve sketched out this pathway below, which might be good to refer back to as we walk through it. Essentially, to get PTFE we need tetrafluoroethylene (TFE). TFE is made from chloroform and hydrofluoric acid (HF). To get HF, we need fluorite and a strong acid - sulfuric acid is what’s used industrially, but I’m going to argue that hydrochloric acid (HCl) could work alongside a catalyst to simplify the pathway. To get chloroform, we can mix ethanol and bleach. Of course, bleach isn’t a great food for living things so we should also synthesize that from ozone and NaCl.

Diagram of PTFE synthesis from plausible natural ingredients

The majority of the starting ingredients can already be synthesized biologically from normal feed, specifically ethanol, NaCl, and HCl. Ozone could be obtained in parts-per-billion quantities from normal air, which means that the only base ingredient we need to add to their normal food is fluorite.

Now, we should note that there are a couple immediate problems with this pathway. First of all, many of these reactions don’t occur at room temperature and instead require 500+K to occur. However, if we invoke the mystical power of enzymes we can reduce that activation energy to something like internal body temperature.

I use “mystical” to describe enzymes here, but they’re not magic or handwavium - just biological catalysts. Catalysts reduce the activation energy of a reaction by organizing, stabilizing, and orienting the molecules in such a way that it’s no longer brute-force random noise (high temperatures) that allow a reaction to go to completion, but instead a choreographed dance.

Second of all, most of these ingredients are awful. I’ve compiled here a list of the warnings on Wikipedia about various chemicals we’re using:

Ozone is one of the greatest oxidisers we know of, which is why it’s so dangerous. We can smell it at ~1-2 ppb (parts per billion), and it’ll start to damage us at ~100 ppb, with an LC50 of ~50 ppm (parts per million). Given these restrictions on the concentration of one of our reactants, this may be a very slow reaction even when operating at near-lethal concentrations.

Bleach is used to kill things. Plain and simple. We use it in bio labs to get things really really clean, and after we do so we usually label them “not to be used with sensitive organisms”. Here’s the warnings from Wikipedia:

“... ingestion of bleaches can cause damage to the esophagus and stomach, possibly leading to death. On contact with the skin or eyes, they may cause irritation, drying, and potentially burns. Inhalation of bleach fumes can damage the lungs.”

Chloroform is also pretty terrible for humans - that’s why we pass out when we sniff it, and why it can kill us if we consume more than a thimbleful of it. Here’s some Wikipedia warnings:

”Prolonged dermal exposure can result in the development of sores as a result of defatting.” “Accidental splashing into the eyes has caused irritation.” “... causes depression of the central nervous system (CNS), ultimately producing deep coma” “use of chloroform [for anesthesia] has been discontinued because it caused deaths due to respiratory failure and cardiac arrhythmias”

Acids are not great for humans. They won’t melt you (well, most of them) but they can quickly ruin your day. Here, we’re talking about some of the worst. Sulfuric acid is pretty terrible stuff and hard to synthesize, so I opted for the tamer hydrochloric acid (HCl). It’s possible that you could synthesize sulfuric acid biologically, but HCl and an enzyme will probably work just as well together. However, it’s worth noting that HCl is still pretty terrible. We humans synthesize this stuff naturally for digestion in the stomach, where it constantly eats away at our mucus linings and causes heartburn and ulcers when it escapes.

But neither of those acids compare to hydrofluoric acid (HF). This stuff has been described as “movie acid” because it’ll eat through, like, everything. Metals, organics, whatever. The first video that pops up when you search for HF is “flesh eating acid”. The OP didn’t include HF in his acid cows because even PTFE is permeable to it. Please sir, may I borrow a little of that unobtanium?

Finally, tetrafluoroethylene (TFE) is not fun stuff either. I couldn’t find any specific hazards associated with it besides “weak carcinogenic effects” but it’s given 3/4 for health hazard, 4/4 for flammability, and 3/4 for reactivity by the NFPA, better known as the “fire diamond”.

And all of the above assumes that you’ve managed to insert suitable genes for these various, custom-designed enzymes into their genetic code in such a way that they’re properly duplicated, transcribed, and translated. Most enzymes (proteins) aren’t stable under strong acids, instead hydrolyzing into individual amino acids... which also aren’t stable under low pH. Also, DNA falls apart under low pH.

Fun, right? Your genetic engineers probably hate you and have all quit. You’ve turned your cows into essentially fume hoods for synthetic chemistry, and they’re unlikely to be much more than a pile of chemicals after a while. And they all have cancer. Oh, and while they were alive, you fed them rocks.

Cool question, murderer!
    - a vegan somewhere, probably

Tissue linings

You can pick whatever tissue you want to line with PTFE. I initially thought that the stomach would be a good choice for this because it’s already dealing with acids, but the substances we’re working with are so far beyond “normal” acids that the 5-6 pH unit difference body tissue and stomach tissue is blown out of the water by the ~20 pH unit difference between body/stomach tissue and fluoroantimonic acid. If your genetic engineers have succeeded at all of the above, they’ll have no problem turning the cow’s head or hooves into acid cauldrons. Which really begs the question of why we’re using cows at all.


So, the problems listed above arose from the creation of a single cow. You’re interested in making 264 million of them. I can not express strongly enough how much I would advise against this course of action. Problem #1 being that we’d actually run out of rocks to feed them. We’d also run out of ozone and have to synthesize that artificially, which the environmentalists will not be happy about because it’s a major pollutant at ground level. Heck, we’d even put a dent in the world ethanol supply.

Possible saves

Biologically synthesized PTFE fails the ‘reality-check’ really hard. However, there are some options if you’re willing to be a little flexible.


Biological silica production is a real thing. Diatoms make their frustules out of glass by secreting silica nanospheres which they then glue together. Glass is vulnerable to erosion by fluoroantimonic acid, but so is our stomach mucus vulnerable to normal HCl -we just secrete it continuously. I’m also confident your genetic engineers would be happier to insert eukaryotic diatom genes into a eukaryotic cow than archaeal bacterial ones.


As pointed out in a comment, waxes might also be a way to store these acids. Again, they’re not immune to the results but constant secretion might also solve that problem. In fact, they’d probably react with the acids themselves and substitute fluorines in place of the hydrogens, which would create a structure very similar to PTFE anyway. Even better, cows already produce fats which would simply need to be elongated/saturated, or you could borrow some honeybee genes (wow, same kingdom even! Maybe you’ll be able to re-hire some of your old engineers now that you’re making such reasonable requests) and do wax production directly.

Good luck!!

(Shoutout to the Answer Sandbox for some help developing this answer!)

  • $\begingroup$ Just to make the long post easier to read, do you mind moving the alternate solutions to the top and mentioning that it fails the reality-check, and then explaining why further down? (Great post, by the way.) $\endgroup$ Jul 6, 2018 at 13:28

Let's assume a more complex process. The comments are correct that biologic, glandular tissue cannot protect itself against the acid. The problem requires that the acid both be contained, and that it be produced by a cow.

Let's suppose a complex chemistry when the mammary glands produce the precursors. To prevent the glandular tissue from being destroyed, there shall be several types of glands which produce a reactant. Let's also suppose some solvent, which from the comments must not be water.

The precursors are expressed into the milk ducts, which are muscularly restrained to prevent backflow to the glands. The milk ducts each conduct their particular chemical to mix with the next chemical, which then further reacts until eventually, the ideal gruesome mix reaches the udder.

The ducts are lined with materials that are impervious to the precursors and the products. Until the final steps, these may be able to be semi-permeable, so that water may be removed from the mixture, which concentrates the milk. It is also necessary to get all the water (if there was any) out of the milk before it is mixed with the fluoroantimonic acid, which can not exist in water solution.

The synthesis methods carried out in the mammary glands are beyond my knowledge of chemistry. At the least, you will need this sequence of synthesis approach, with the milk ducts becoming pure, non-permeable PTFE by the end.

The good news is that the cow can reuse the fluorine handling enzymatic systems both to make the PTFE and the fluoroantimonic acid.

Heaven help the calves looking for a meal.

  • $\begingroup$ A little tip about markdown: you need to hit Enter twice for a paragraph or have two spaces at the end of a line before hitting Enter once to get a soft linebreak, though most people prefer paragraphs. There is a little bar at the top of where you type your posts that can help you with markdown and you can also click on "suggest an edit" on other peoples posts to see their markdown if there is something you would like to use in your own posts (no need to submit the "edit" in such a case). $\endgroup$
    – Secespitus
    Jun 29, 2018 at 17:39
  • $\begingroup$ Thank you @Secespitus. I really need to spend some quality time with the markdown instructions. Is markdown fairly common now, or is it unique to SE? $\endgroup$
    – cmm
    Jun 29, 2018 at 17:51
  • $\begingroup$ Personally SE is the only place where I am regularly using markdown, but as far as I know GitHub supports it and I've heard that a lot of text editors are using it. Writing.SE is a smaller site, but they have a couple questions about markdown, which indicates that it's used in that area. And there are lots of questions on SO. $\endgroup$
    – Secespitus
    Jun 29, 2018 at 18:00

You need a molecular assembly style process.

Protein synthesis is accomplished by adding the correct nucleotide to the end of the chain and repeating until the protein is complete.

A similar molecular assembly process could convert long-chain hydrocarbons into long-chain fluorocarbons. I am not able to design the needed assembler, but I think it as least passes the plausibility test. A somewhat rigid assembler could walk down the chain (able to constrain the current section of the long-chain molecule during construction) , replacing hydrogen with fluorine 1 atom one at a time.

The assembler will require a steady source of fluorine, which is common in many foods as well as water sources. Too much fluorine is toxic, but with the right balance of intake and usage, this is also feasible.

It will be necessary to coat every organic surface in contact with your nasty acid. This limits the ability of the body to handle cell growth / death / replacement because a PTFE layer must remain in place at all times. The surfaces could be designed so that it sloughs off gradually allowing cell growth on the inner layers, and PTFE coated dead layers actually in contact with the acid to form the safety barrier.

You still have a problem, how do you get the PTFE to adhere to the underlying cells. The methods uses commercially are not going to work inside your cow. Might I suggest that the solution for this is constructing the PTFE/cell boundary into something similar to Velcro. This will not be a strong adhesion (especially if the cell material is the lipids layer used in animal cells), but it could be strong enough since it does not have to survive high shear / sliding stress, etc. common to to skin.


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