Ketchup is a non-Newtonian fluid | Hacker News Reader

Ketchup is a non-Newtonian fluid

scientificamerican.com

132 pointspseudolus82 comments

So we should be able to walk on the surface of a pool filled with ketchup?

I've seen this video of people walking on custard on brainiac: https://www.youtube.com/watch?v=Iz9KnPZWOgs

No, ketchup is shear-thinning, meaning it’s less solid when under stress.

I wonder if these properties are used in analog devices... I recently learned that ovens had thermal switches based on wax (and expansion under heat).

https://en.wikipedia.org/wiki/Dilatant#Applications

I'd say that shear thickening fluids as used in traction control systems can be seen as an analog clutch.

ahh sadly the kevlar-fluid combo is already a thing.. i always thought it would be a fun thing to build

The lock in a washing machine door works like that, which is why it takes two minutes to unlock.

I had assumed it was magnets!

magnetic wax

Melting / Solidifying wax is also the basis of old-school steam radiator thermostats.

And current-day car thermostats. If it fails, your engine overheats, and that's an expensive repair. If you ever see a high temp warning light on your car, you can take it out and test its functionality in a pot of hot water (or replace it for ~$20)

Also, was how the lunar rover handled cooling. Big block of wax used as a radiator. Well, not radiator exactly!

I don't think the LM used wax for thermal management, but the Lunar Roving Vehicle did, as a "thermal capacitor" [1]. That is, heat was stored in a block of wax while driving, and then radiated away between uses.

[1] https://en.wikipedia.org/wiki/Lunar_Roving_Vehicle#Wheels_an...

That’s what I said. Lunar rover.

https://en.wikipedia.org/wiki/Wax_motor

If you've flown, you put your life in a wax motor's waxy hands: "Wax motors are used...to control fuel, hydraulic, and other oils critical to safe flight today in modern airplanes."

Even today the thermostatic valves you find on home heating radiators are actuated by wax.

Yes, he needs to fill the pool with a dilatant fluid not a thixotropic fluid.

Braniac is back? I miss that show

Unlikely - a spoon sinks in it.

Just because it's non-Newtonian doesn't mean it's identical to oobleck. All it means is that it's not Newtonian.

Besides, you can run on water (or at least, some lizards can) at high enough speeds, though I'm not sure if water still behaves Newtonian in those situations.

For a human-sized object running on water, it's more about inertia - viscosity doesn't really come into it at that speed and scale. In other words, the Reynolds number is high in that situation.

Shake and shake

The ketchup bottle.

None'll come,

And then a lot'll.

As someone who can use almost an entire bottle of Heinz 57 on an order of French fries, this made me laugh. Whenever I ask for ketchup at a restaurant and they bring me “only” 4 packets, I do my best not to roll my eyes in disappointment because I know how ridiculous I am.

If I were you, I'd slow down with the ketchup alright, that sounds obsessively much. Consider that commercial ketchup tends to have lots of sugar and sodium.

Armchair nutrition advice on the internet, that’s a first! What’s next? Ice cream and cigarettes are bad!?!? The gall!

It’s alright. I balanced it out with a Diet Coke.

You could have a problem processing the red die.

Doesn't sound ridiculous. Those little plastic packs with enough sauce for just a few chips are ridiculous! Anywhere that does that shouldn't be allowed to call themselves a restaurant. I guess the idea is people will never ask for enough packs, so they save sauce. Uses a lot of plastic though, not to mentioning ignoring what the customer wants.

My Grandma said:

Silly silly ketchup bottle

First a little

Then a lottle

Same meaning :)

I find this with some brands but not with others, so assumed it was a solved problem and some manufacturers are just cutting corners on bottle design. Is this not the case?

Through decades of experimentation, I have proven that hitting the 57 on the bottle is the best way to get the shearing force going.

I've always heard this is by design.

Hold the bottle in one hand as normal and instead of hitting the back of it, hit the underside of your wrist instead ie hitting upwards not downwards.

The bottle and the liquid are two "things" which are loosely connected together via "fluidy" friction etc. When you hit the back of the bottle, you are effectively trying to force the bottle around the ketchup that is trying to dribble out downwards. Gravity is trying to drag the ketchup out. The impact will make the ketchup a bit more liquid. Some ketchup will flow. We know it does because it does!

When you make an impact upwards, then you are making the bottle try to leave the ketchup behind (inertia). Combine that with gravity and the impact liquidising the ketchup and more of the stuff comes out.

There are other considerations such as the shape of the bottle. If you want the fastest deposition then probably something like a conical bottle with 45deg at the apex or whatever minimises internal surface area for a given contained volume. However that will dump an entire bottle in one go and you will impale your hand if you tap the back of it. It's quite a tough problem. The squeezy jobbies seem like a bit of a cop out somehow!

Assume a spherical, infinite ketchup bottle. Be careful with your aim.

Don't hit the bottle. Keep the lid on, invert, and shake vigorously, until flow. Then remove the lid and shake gently to apply.

That's also Heinz's own recommendation.

* https://hpsauce.co.uk/trivia

Are you still able to find the glass bottles? I read a couple years ago, to my dismay, that Heinz was discontinuing them.

Yes! And it's the opposite of oobleck. Meaning, it is shear-thinning (mayo is similar)

There's also a 3rd category, the thixotropic fluids, they do become thinner with stresses but they take a while to solidify again

I was trying to find the best way to clean copper pots. Sometimes people note that ketchup works, but it's hardly cost effective. The most basic option seems to be salt and vinegar, but what could you add to it (from a minimalist perspective) to give it the clinging consistency and homogeneity of something like ketchup? I thought maybe cornstarch, but it did not suspend; it settled out.

I don't have any copper pots, but vinegar is my go-to cleaner around the house. Try adding about 5 to 10 percent by volume to a fully flooded pot and let it soak for an hour or two, bring to a boil of you are impatient. This works wonders for my pots, shower, sink, etc.

You have to boil cornstarch to disperse it. Arrowroot can disperse at lower temperature but it's kind of obscure (around $3–5/lb but lasts a while). Powdered sugar might be a more practical option?

Bar Keepers Friend is great for most copper/metal cookware and other things around the house like sinks as well.

Cornstarch water is shear thickening, wheras ketchup is, I assume, shear thinning.

Cornstarch mixed with water is shear thickening, but when boiled, it becomes shear thinning (AFAIK), and that is basically what ketchup is. If boiling it, you should use way less starch - it goes a long way. You can also use other other flours as well (not sure how different the performmance is), like you would in Béchamel or custards. I think the shear thinning effect comes from starch gelatinization [1].

I don't have time ATM to go through the whole paper, but it seems like [2] is covering exactly this topic in detail.

I think (but [2] might correct me, I'm just guessing at this point, please don't quote me) that there is no special connection between the mixture being shear thickening before, and shear thinning after boiling - just a coincidence in this case.

Source: sciency-cooking dabbler, don't trust what I say too much.

[1] https://en.wikipedia.org/wiki/Starch_gelatinization

[2] https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.85...

neat!

Yeah, I kept doing that for my copper pots once a month with different things: ketchup, bar keepers friend, etc. It was never an easy wipe away experience like I imagined.

The baseline for me is vinegar poured over salt, which magically removes tarnish in seconds without even wiping, in some spots. But in others, it doesn't and then it takes a fair amount of scrubbing.

So what I'm looking for is a way to make the reaction more uniform, perhaps slow it down. Maybe corn syrup.

Put a lid on it, 1 cm of vinegar in it, then boil. Put it under an extractor hood or outside though.

Wet paper towels cling to the walls of a container and suck up vinegar from the bottom.

Hmm, is it possible to add exactly so much corn starch to ketchup that the thinning and thickening effects cancel out?

If it is then most likely only for a particular force applied because it seems unlikely that the effects are exactly opposite?

Edit: it should have occured to me that combining ketchup with thickeners might be a well-researched topic in food science already.

Would make a magnificent youtube video.

> it should have occured to me that combining ketchup with thickeners might be a well-researched topic in food science already.

There were articles during the Gulf War about armed forces being unhappy with thin ketchup, so they brought in standards for flow rate. (I'm struggling to find those for some reason).

Here's the FDA spec for consumer ketchup.

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFR...

> (b) Quality. (1) The standard of quality for catsup is as follows: The consistency of the finished food is such that its flow is not more than 14 centimeters in 30 seconds at 20 deg.C when tested in a Bostwick Consistometer in the following manner: Check temperature of mixture and adjust to 20+/-1 deg.C. The trough must also be at a temperature close to 20 deg.C. Adjust end-to-end level of Bostwick Consistometer by means of the spirit level placed in trough of instrument. Side-to-side level may be adjusted by means of the built-in spirit level. Transfer sample to the dry sample chamber of the Bostwick Consistometer. Fill the chamber slightly more than level full, avoiding air bubbles as far as possible. Pass a straight edge across top of chamber starting from the gate end to remove excess product. Release gate of instrument by gradual pressure on lever, holding the instrument down at the same time to prevent its movement as the gate is released. Immediately start the stop watch or interval timer, and after 30 seconds read the maximum distance of flow to the nearest 0.1 centimeter. Clean and dry the instrument and repeat the reading on another portion of sample. Do not wash instrument with hot water if it is to be used immediately for the next determination, as this may result in an increase in temperature of the sample. For highest accuracy, the instrument should be maintained at a temperature of 20+/-1 deg.C. If readings vary more than 0.2 centimeter, repeat a third time or until satisfactory agreement is obtained. Report the average of two or more readings, excluding any that appear to be abnormal.

This is what I come to HN for.

Mind blown that ketchup is such a specific science like this.

And here's one in action (with what appears to be ketchup): https://youtu.be/z_44kDWdhw8?t=53

Haha. That driving rock music is so...incongruous.

There is a paper where the authors use ketchup for polishing high precision lenses. The especially want to have the property of the shear-thinning for best results: https://www.spiedigitallibrary.org/conference-proceedings-of...

To be clear, there are better polishing agents in the scenarion than ketchup. On of the authors mentions that they wanted to do some research that could get them the IG Nobelprice.

> To be clear, there are better polishing agents in the scenarion than ketchup

Like, chocolate? https://www.wildwoodsurvival.com/survival/fire/cokeandchocol...

Also true for (some?) honey[1]. I remember learning about Ketchup and that, among many other things, from the Einstein Anderson books[2] when I was a child.

[1] https://www.sciencedirect.com/science/article/abs/pii/S02608...

[2] https://www.goodreads.com/series/101369-einstein-anderson

> Ketchup is famous for being hard to get out of the bottle

Whatever happened to that LiquiGlide stuff that was touted 10 years ago? Why isn't it everywhere?

Probably patented

Or carcinogenic.

Yes, the process is patented by them [1]. But they've been trying to commercialize it.

It just appears that if you're making something cheap and high-margin like ketchup and putting it into disposable plastic bottles, it's probably more cost-effective for you if the customer throws away an almost-empty bottle and buys a new one, than if you spend more on the fancy coating so the customer can get every drop.

[1] https://liquiglide.com/tech/

According to their FAQ, they have a product entering the market within the next year or so.

> Is there a product in the market with LiquiGlide?

> Not yet. We expect to see the first commercial applications of LiquiGlide in the next year.

For those who disagree that the squeeze-bottle solves the problems...

How about packaging ketchup in wide-mouth jars, as is often done with salsa?

There's no need to change the packaging, it's a solved problem that hasn't been implemented for monetary reasons.

https://news.mit.edu/2015/liquiglide-condiments-0630

If it’s being used for certain mayonnaise packaging in Europe (where mayonnaise is the “ketchup” of the continent), I can’t imagine lack of ketchup market penetration is for cost reasons alone.

What monetary reasons?

Producers not interested in consumers buying less of their product?

Asking honestly how does this work?

If I as a producer need to manufacture 100g of something, whether it’s all consumed or not I still need pay to produce all 100g, what benefit is there in paying to produce something that doesn’t get consumed?

Let's say all consumers collectively eat X kg of ketchup per month. If 10% gets left on the bottle walls, they are buying 10% more, thus ~10% more profit for producers.

It works the same way we are using much more laundry detergent and toothpaste than necessary.

I have an umbrella with a similar surface. It gets noticeably damaged over time and loses effectiveness, so I'd be wary of using it with food and particles from the damaged surface falling into the food.

Use a squeeze bottle. Problem solved

And mustard?

Is this not common knowledge?

I remember hearing about this quite a few years back on some youtube science channel..

Never underestimate the joy people derive from hearing something they already know. -Enrico Fermi ref: http://www.pas.rochester.edu/~tim/quotes2.html

i loved ketchup before this article and now i love it even more.

my toddler begs to differ. I will be cleaning the floors now.

Is solving the ketchup bottle problem like nuclear fusion, the solution is always 10 years away?

The flexible plastic bottles mentioned in the article are just as bad, for some reason they make them very thick.

Anyone know why ketchup doesn't come in a toothpaste like tube? That feels like it should work. What am I missing?

It's probably a sizing issue, given how much ketchup gets used, you'd need a lot of toothpaste tubes, and making them huge would lead the the same issues as you get with other containers.

Perhaps it's because the vinegars can settle out, so you want to shake the bottle? You can't do that with a tube.

I thought the article's reminiscing a bygone era now that the plastic bottle have sort of won?

I find them perfectly adequate to be honest, the full on red ones, or the upside down supermarket types...

It does, you’re missing “ketchup in plastic pouch” google search.

My supermarket here in the Netherlands has most condiments in such tubes. I like them in outdoor situations, like when going camping or in the park. They're more messy than bottles or jars when used on a table, which is why I think that packaging is relatively niche.

Hold the bottle parallel to the plate and tap it gently against your other hand. The ketchup comes out easily. It’s only hard to get out if you hold the bottle upside down (like you would with anything else). ;)

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