The Stress Ball Squishiness Experiment

Questions We Had to Answer

This experiment centers on a question you, like us, probably hadn’t considered before: What is squishiness?

The answer I came up with is, when you squeeze something, how easily does it give way? If the answer is “very easily,” the thing is very squishy. If the answer is “not easily” it is not squishy – or unsquishy, to use a technical term.

Here are some common examples to get us all on the same page:

• Jell-O: Extremely squishy – quite possibly the squishiest substance ever invented.

• Tomatoes: Moderately squishy.

• Butter left out in the summer: Very squishy.

• Butter straight from the fridge: Very unsquishy.

• Bricks: Extremely unsquishy (don’t even try it).

That answer prompted a follow-up question: How do you objectively measure squishiness? The method we came up with was measuring how hard we needed to squeeze a thing to make it give way. In other, better words: How much force do I need to apply to this object to make it compress a specified distance?

How We Tested Squishiness

I’ll tell you what we didn’t do, we didn’t google “squishiness testing machine,” because that would be embarrassing. Ahem.

We could have found some stressed-out people and asked them to systematically squish and rate our stress balls. But that wouldn’t be objective, and besides, people under stress don’t tend to be up for taking part in unpaid science experiments.

Instead, we got the kind of motorized stand that’s usually used for lab-testing industrial equipment. Its real name is the Mark-10 ES30 Motorized Test Stand. Until somebody stops me, I’m going to call it the Squishomatic. We also got a force meter, also called a force gauge, also called (exclusively by me) a force-o-meter. And a very large pile of our best-selling stress balls.

Two important pieces of information:

1. 1

   The Squishomatic is a stand with two round, flat metal plates. One acts like a base where you can put stuff, and one lowers automatically when programmed. You can see it in action in our videos.

2. 2

   I’m talking about stress balls, but just know that these are all different shapes. My personal favorite is called “Cool Dog,” and you can tell he’s a cool dog because he wears sunglasses. I also enjoy the unhinged chicken.

OK, here’s what we actually did:

1. 1

   Placed the stress ball victim on the lower plate of the Squishomatic. This is super easy if it’s a truck or a turtle, less so if it’s a round. And so many of them are round.

2. 2

   Attached and calibrated the force gauge.

3. 3

   Set the top plate of the Squishomatic: We told it to move until it was 0.2” from the bottom plate.

4. 4

   Started the Squishomatic squishing, and the data software recording force measurements.

5. 5

   Once the Squishomatic’s top plate had traveled its set distance, waited five seconds, then raised the top plate.

Units of Measurement

We measured our results in pound force. If you already know what that means, good for you, skip ahead. Or feel free to judge my explanation. If you don’t know what it means, or you’ve heard of it but don’t really understand, don’t worry: I found out so you don’t have to.

The short answer: On Earth, where this experiment was conducted, 1 pound force (lbf) = 1 pound (lb).

The long answer: Although we commonly use “pound (lb)” in reference to both mass and weight, they’re actually two different types of pound. Mass is measured in pound mass (lbm) and weight is measured in pound force (lbf). If you’re wondering, what even is the difference between mass and weight, welcome: you’re in good company.

Mass measures how much of something there is, while weight measures how much force that mass exerts on its environment – which on Earth, means how that mass is affected by gravity. (Specifically, weight = mass x gravitational acceleration.) Gravitational acceleration on Earth is always the same: 32.1740 ft/s2. (Physicists: now is not the time.) But the bigger the mass, the more of it there is for gravity to pull on, so the higher its weight.

Here’s a useful experiment you can do to understand the difference. Buy a cake. (Or any food item.) To test its weight, pick it up. That pushing force you feel on your hands is the combined effect of the cake’s mass and the gravity acting on it. To test its mass, eat it! Every mouthful and crumb constitute part of the cake’s mass.

Converting lbm to lbf, and vice versa, is so easy you can do it in your head. That’s because 1lbf is defined as 1lbm under the effect of Earth’s gravity. So a cake with a mass of 5lbf weighs 5lbf.

Essentially, pound force serves as a shortcut way of acknowledging the relationship between weight and mass. When you see a weight of 10lbf, you know that it’s an object with a mass of 10lbm that’s being impacted by the Earth’s gravity.

The Videos

Watching stress balls get squished might be more stress-relieving than squeezing them ourselves.

Results

Since the Push Pop Bubble Stress Ball required the least amount of force to compact, we can officially name it the squishiest stress ball in our test. Which makes the Basketball Stress Ball (Q154) the least squishy.

There was an 8.3lbf difference between that least squishy basketball stress ball and our second squishiest stress ball. (The Push Pop Bubble Stress Ball proved to be a bit of an anomaly – we’ll get to it.) That’s a bit less than the force required to crush an egg in your hand.

To make the results easier to digest, I focused on the peak force the machine hit while squishing each stress ball. In other words, the maximum force required to compact each one. All but the Push Pop Bubble Stress Ball had peak forces of over 180lbf, and most of those (74%) were over 185lb.

To understand just how much force that is, here are some real-life comparisons. Imagine that the stress ball is on the base plate of the Squishomatic, and this thing is standing (or sitting, I guess) on top of the top plate.

Q#	NAME	IMAGE + CLIP	PEAK FORCE (LBF)	THING OF ROUGHLY EQUIVALENT WEIGHT
Q154	Basketball Stress Ball	Watch Clip	190	A male English mastiff
Q14119	Horse Stress Reliever	Watch Clip	187.15	A female Sumatran tiger
Q43715	Building Block Stress Toy	Watch Clip	184.9	A small refrigerator
Q13906	Heart Stress Reliever	Watch Clip	181.7	Two twin size mattresses
Q90548	Push Pop Bubble Stress Ball	Watch Clip	162.2	A full ½ barrel keg of beer

That’s a lot of force! Way more force than any person could exert through grip. The average grip strength for ages 20 to 69 across both hands is 97.4lb for men and 60.2lb for women. And all of the stress balls bounced back to their original shape within seconds of the Squishomatic lifting off them. So it’s safe to say that no matter how stressful a day you’re having, you’re not going to destroy that stress ball.

As you can see, the Push Pop Bubble Stress Ball required much less force, and was therefore significantly squishier than even its closest contender. Unlike all the other stress balls in the experiment, this one is made of a soft, jelly-like plastic, instead of strong, foamy plastic. This made it much less resistant to the Squishomatic’s squishing. (It’s also one of the most enjoyable videos.)

Key Findings

Shape does not appear to determine squishiness

Going into this, I assumed that certain shapes would be squishier than others. I wasn’t clear on which shapes – maybe it would be harder for the machine to squish shapes that were already flat, like the hockey puck, or shapes that had some thickness to them, like the van and semi-truck.

Sometimes, there was a correlation between shape and squishiness. For example, two of the hockey pucks (Q491 and Q13922) were made by different manufacturers and were within 0.2lbf of each other. It was the same story with the two stars, which had a 0.25lbf difference, and two of the brains (Q13918 and Q670) which were only 0.05lbf apart. However, in other cases, the same shape from different manufacturers experienced significantly different peak forces: see the hearts, the spheres, and the footballs.

Stress balls from the same manufacturer tend to show similar squishiness levels

Our stress balls came from five different manufacturers. When we ranked all the stress balls by peak force, we noticed multiple instances where several stress balls from the same manufacturer were grouped together, producing peak forces within 0.5lbf of each other.

This probably indicates subtle differences in the formulas manufacturers use to create stress balls. All but one of our stress balls are made of polyurethane (PU), a type of plastic foam. PU is made by combining two chemicals and a catalyst right before it’s squirted into the mold, where it turns from liquid to foam. Differences in that PU mix can result in different densities, and manufacturers often produce PU stress balls at a range of densities. For example, one of our manufacturers told us that their stress balls range from 0.175 – 0.25g/cm³.

This seems like the most likely explanation for why different PU stress balls are different degrees of squish, even when they’re a similar shape.

What is optimal stress ball squishiness?

The Squishomatic told us how much force it had to apply to compress (squish) each stress ball – but it couldn’t tell us which ones were the most fun to squish. (That would have been one point in favor of our stressed-out focus group.) Which means that you have to take our data and decide your personal squishiness parameters.

Although 50 of our 51 stress balls all had peak forces within 8.3lbf of each other, that’s enough to notice a difference between the squishy and the firm. For maximum squishiness, choose from the stress balls with lower peak forces. If you like a stress ball with some resistance, look at those with the highest peak forces.

I’d also recommend considering size and shape. The Squishomatic doesn’t care about these, because it is a supreme squishing machine without opposable thumbs. But the smaller and more ergonomic your stress ball, the more satisfying it is to squish.

The Bottom Line

It’s hard to look at a photo of a stress ball and understand what it would be like to squish it. And that’s important information – maybe the most important information you can have when it comes to buying stress balls. (Unless you, like me, value stress balls exclusively based on whether they are shaped like a Cool Dog or not.)

Rather than squishing every stress ball by hand, we deployed the Squishomatic. It’s given us a useful, objective dataset of squishiness levels, which you can use to choose the right one for you. Or you can listen to your heart and choose the unhinged chicken.

Q#	NAME	IMAGE + VIDEO	MANUFACTURER	PEAK FORCE (LBF)	VIEW PRODUCT
Q154	Basketball Stress Ball	Watch Clip	A	190	View Product
Q43987	Round Stress Toy	Watch Clip	D	189.45	View Product
Q43625	Turtle Stress Toy	Watch Clip	D	189.1	View Product
Q43863	Rainbow Brain Stress Toy	Watch Clip	D	188.8	View Product
Q1942	Chicken Stress Ball	Watch Clip	A	188.4	View Product
Q43775	Cool Dog	Watch Clip	D	188.2	View Product
Q13909	Football Stress Reliever	Watch Clip	C	188.05	View Product
Q43743	Service Van Stress Toy	Watch Clip	D	187.95	View Product
Q91001	Golf Cart Stress Reliever	Watch Clip	C	187.8	View Product
Q488	Heart Stress Ball	Watch Clip	A	187.7	View Product
Q71390	Hockey Puck Stress Ball	Watch Clip	B	187.7	View Product
Q43640	Eyeball Stress Toy	Watch Clip	D	187.55	View Product
Q305	Hard Hat Stress Ball	Watch Clip	A	187.55	View Product
Q13914	Earth Stress Reliever	Watch Clip	C	187.2	View Product
Q71360	Brain Squeeze Toy	Watch Clip	B	187.15	View Product
Q14119	Horse Stress Reliever	Watch Clip	C	187.15	View Product
Q13911	Basketball Stress Reliever	Watch Clip	C	187.1	View Product
Q246	Capsule Stress Ball	Watch Clip	A	187.1	View Product
Q43692	Hard Hat Stress Toy	Watch Clip	D	187.1	View Product
Q43637	Tooth Stress Toy	Watch Clip	D	187	View Product
Q43753	Semi Truck Stress Ball	Watch Clip	D	186.8	View Product
Q43731	Gallon Drum Stress Toy	Watch Clip	D	186.7	View Product
Q670	Brain Stress Ball	Watch Clip	A	186.55	View Product
Q13912	Soccer Ball Stress Reliever	Watch Clip	C	186.55	View Product
Q13918	Brain Stress Reliever	Watch Clip	C	186.5	View Product
Q13910	Golf Ball Stress Reliever	Watch Clip	C	186.45	View Product
Q43833	Whale Stress Toy	Watch Clip	D	186.35	View Product
Q676	Small Football Stress Ball	Watch Clip	A	186.25	View Product
Q70194	Round Foam Stress Ball	Watch Clip	B	186.2	View Product
Q43628	Corn Stress Toy	Watch Clip	D	186.15	View Product
Q71358	Soccer Stress Ball	Watch Clip	B	186.15	View Product
Q71386	House Shaped Stress Ball	Watch Clip	B	186.1	View Product
Q71355	Dice Shaped Stress Ball	Watch Clip	B	186.05	View Product
Q13922	Squeezable Hockey Puck Stress Reliever	Watch Clip	C	185.75	View Product
Q13908	Baseball Stress Reliever	Watch Clip	C	185.65	View Product
Q491	Hockey Puck Stress Ball	Watch Clip	A	185.55	View Product
Q43909	Toilet Bowl Stress Toy	Watch Clip	D	185.05	View Product
Q43715	Building Block Stress Toy	Watch Clip	D	184.9	View Product
Q62985	Poop Emoji Stress Ball	Watch Clip	C	184.9	View Product
Q13932	Star Stress Reliever	Watch Clip	C	184.5	View Product
Q14038	Breast Stress Reliever	Watch Clip	C	184.25	View Product
Q17459	Round Stress Reliever	Watch Clip	C	184.25	View Product
Q2106	Star Shaped Stress Ball	Watch Clip	A	184.25	View Product
Q43951	Metro Bus Stress Toy	Watch Clip	D	184.15	View Product
Q653	Round Stress Ball	Watch Clip	A	184.05	View Product
Q679	Soccer Ball Stress Ball	Watch Clip	A	183.95	View Product
Q13948	Apple Stress Reliever	Watch Clip	C	183.75	View Product
Q17435	Drop Stress Reliever	Watch Clip	C	183.5	View Product
Q152	Baseball Stress Ball	Watch Clip	A	182.15	View Product
Q13906	Heart Stress Reliever	Watch Clip	C	181.7	View Product
Q90548	Push Pop Bubble Stress Ball	Watch Clip ✖	E	162.2	View Product