I've got two.

A lab freezer's seal broke in the middle of a humid Michigan summer, so everything got encased in frost. In the process of chipping away the frost, the ink on many of the labels rubbed away, so we essentially had a bunch of mystery flasks. One such flask had a septum that was stuck really tight. When I yanked it out, the recoil caused some of the mystery liquid to splash onto my mesh shoe. Within a couple minutes, my foot started stinging. We later identified the contents to be acetyl chloride, so it was probably reacting with my foot sweat to make acetic acid and hydrochloric acid. I took my shoe and sock off and rinsed my foot in the lab sink.

I was putting sodium hydride into an empty round bottom and a good bit of it got stuck to the ground glass in the neck. Genius that I am, I turned a nitrogen line on with low flow thinking I could blow it into the flask. I didn't realize that the nitrogen had to go somewhere and the only place it could go is back out, blowing NaH all over my face. There was very much safety-glasses-unless-there's-an-inspection culture at my old university, but I was never more thankful that I made it a personal rule to wear splash goggles. Would not have liked for the moisture on my eyes to bubble off.

Not as cool as the original story, but I was working with a big carboy of dilute HCL in a CHEM 101 lab. The previous person that used the carboy had managed to spill dilute HCL all over the stopper. I was not aware of this.

The protocol was to grasp the stopper between middle and ring finger, pull it out, then pick the carboy up with both hands and pour into the beaker. That way, the only thing the business end of the stopper ever touches is the inside of the carboy.

I'd just started pouring when I felt the skin between the two fingers start to itch. It was obnoxious, but I had a heavy piece of glassware in my hands trying to measure out a precise amount. So I ignored it until it started to burn. By that point I almost had enough in my beaker so I topped it up. Then I lowered the carboy and replaced the stopper.

Then I ran over to the sink, turned it on full blast, and washed the acid off my hand. I had a red, tender patch there for days. After that, I always wiped the stopper off with a paper towel before I pulled it out.

Warning: FAFO is not a good way to learn about hydrofluoric acid.

When working in a 100 degree server room on some solar batteries (AC was still being installed), sitting on the floor in your sweaty underwear and pants will give an 52V positive terminal a path to ground, though the contents of your underwear.

Unfortunately it was significantly on the pain side of the pain/pleasure scale of my nether region.

body weight acts upon pool cover... i was a kid and almost drowned

I have a small concrete patio inside my house that is open so it's perfect for the pets (2 cats and 2 dogs) do poop and pee. I went traveling for 2 days and left the pets home and when I came back there was a lot of pee. I was out of cleaner and, since I'm a genius, I used BLEACH to clean the pet piss. Well, we had to evacuate because I just created a chemical weapon inside my house. Almost fainted.

I was seven.

My dad didn't give me a paintbrush so I made one by taping a chunk of styrofoam to a stick so I could paint my wooden airplane. It was oil based paint.

When my war vet father saw the styrofoam dissolving, he grabbed the can away from me, remembered the cigarette in his mouth, then shoved it back and made me put the lid on first.

And that was when I learned how to make ~~nitro glycerine~~ *napalm.

Put some lye and aluminum foil in a cup without a handle.

Place a can over the cup with a small hole.

Wait a bit.

Light the hydrogen.

It will also hurt a lot if your finger is on top of the can when you light it because the can will simply dissapear for few seconds.

What i tell you now must never be repeated to my parents. I will deny every word, except for the latter part that resulted in me burning a hole in the driveway since they already know about that.

When I was a teen, I spilled some gas on the concrete floor of the garage while filling up the lawn mower. I thought to myself, "What's the fastest way to clean this up?" Clearly the fastest option was to burn it. This did in fact work and produced a controllable flame, but I had neglected to move the closed plastic gas can away from the puddle of gasoline. As it turns out, plastic is made of flammable petrochemicals. The outside of it immediately caught on fire.

I realized that if the gas can lost structural integrity, gas would flood the garage floor, likely setting the whole structure ablaze. So, I picked up the flaming jug of death and ran out of the garage, setting it in the middle of the asphalt driveway downwind of any important structures. I now had the task of putting out a gasoline fire. How could I do this? Obviously, the best way to put out a fire is to spray it with a hose. So I grabbed the garden hose and aimed the nozzle at the melting jug of death.

This did not work. As it turns out, gasoline floats on water, and as such spraying water on a gasoline fire simply increases its surface area. It roared like a bonfire and the plastic can rapidly collapsed. Additionally, it turns out that asphalt is mainly composed of tar, which is a flammable petrochemical.

At some point I realized I had no idea what I was doing and called the fire department. By the time a fireman arrived, all that remained of the blaze was a smoking hole in the driveway the size of a small child, which was extinguished with a handheld chemical extinguisher.

My dad, at the time, was in charge of the safety training at the local chemical plant. My attempt to extinguish the flaming jug of death made an appearance in one of his PowerPoint slides as an example of what not to do with an oil fire.

I was trying to concentrate hydrochloric acid and had it in my boiling flask on a mantle. It was taking a while and I realized I hadn't added a stir-bar, so I tossed one in.

Then the superheated hydrochloric acid flash boiled and shot out of the flask like 8 feet in the air. Fortunately, I was outside.

Early in my career I did tensile testing on adhesive coupons. I was running an experiment to simulate heating and cooling cycles on a bond. I had a nice big thermal chamber from the 1960’s, lined with heating elements (and undoubtedly asbestos), a big old dewar of liquid nitrogen, some thermocouples, and a PID controller the size of a German Shepherd.

Problem is, cold air sinks. My samples are sitting on the bottom of this huge chamber and their temperature is fluctuating wildly every time a bit of LN2 is added. The ancient PID controller cannot cope with my shitty test setup, it’s trying to turn on the damned heaters to control the temperature when I’m trying to go cold and this is a multi-hour test and I just want to go home.

But… I have a cardboard box. Nice, insulative cardboard, just the right height to get my samples off the floor of the chamber and into a zone where the temperature is more stable. I am brilliant! Cardboard box deployed, I can finally begin my thermal cycling.

I learned a few things that day:

• thermal cycles include both hot and cold phases
• the floor of the thermal chamber has much less temperature stability while cooling AND while heating
• specifically the floor contains a heating element and gets ridiculously hot
• cardboard combusts at a temperature much lower than you might expect
• opening the door of a smoking thermal chamber to investigate allows in a rush of oxygen
• rapid introduction of oxygen to a smoldering cardboard box leads to very large exciting pretty flames
• fire extinguishers leave a fine dust of particles all over everything that you will be cleaning up for MONTHS

I remember one time when I was a kid and had read something mentioning spark gap transmitters. I of course found a bit of wire (tie wire because that's what came to hand, not anything insulated) and a radio and was playing around with a 9v battery making little sparks by shorting it with the wire and hearing the radio crackle in response. What I then thought was that if the little battery was making a noticeable effect then a bigger battery would obviously be better.

I got one of the drill batteries and shorted that out with my bit of wire to make a better spark and proceeded to discover that resistive heating is a thing and thin tie wire connected even briefly to a high discharge battery will get very hot very quickly. I ended up with a nice blister line across my fingers and a scar for a few years showing the position I'd been holding the wire...

Not me but years ago the inorganic lab at my uni was tasked with measuring heavy metals in whale fat and did what they normally did back then to disolve test materials. Mix nitric acid and hydrocloric acid in some heavy duty pure quartz reagent tubes, put in sample and microwave.

Well. Turns out mixing triglyceride (fat) with nitric acid and HCl as a catalyst makes nitroglycerine. And what does that do in a confined space and microwaved

It turns expensive heavy duty quartz tubes into expensive quartz dust and a fucked microwave.

I feel boring - only thing I ever had to realize that if you work with solvents with a boiling point close to body temperature and have them in a flask with a glass cork, you shouldn't hold the flask in your warm hands while waiting - because after a few minutes the glass cork flies off and you have to pay for it 😕

Looks like when, as a child, I read on a bottle of bleach to avoid mixing it with acid. The first thing my dumb ass did was to look for a bottle of vinegar...

Water makes explosions worse.

I had put a bunch of dry ice into a Falcon tube (50 mL screw top plastic centrifuge tube) and suddenly realised that I wasn't actually in the mood for a loud bang, so I chucked it into a perspex water bath. The bang was muted but the water spout hit the ceiling and the water bath failed, drenching my supervisor's notes.

Mine is from when I was 14:

I mixed calcium carbide with water inside a glass bottle. Then I closed its lid. Then I waited until I got really concentrated acetylene. What I got was a scar on my right arm, a smaller one just above my upper lip (nowadays hidden by the beard), and a big scratch on my prescription glasses — without them I'd be probably blind from my left eye.

From that I've learned some valuable things:

1. I'm a muppet.
2. I'm a bloody muppet.
3. My mum was also a muppet, for letting me fuck with calcium carbide, sodium nitrate, concentrated sulphuric acid, sodium hydroxide, concentrated ammonia, gunpowder etc., since my teen years. (Guess where I got the calcium carbide from? Her brother's garage!)
4. My dog (rest in peace, Lana; you were the greatest girl) was probably traumatised with loud noises because of me. Now thinking, Lana was also with me the time I melted lead and poured sulphur on it, and instead of getting galena I got a whiff of Hell on my face.
5. You can tell people a different story every time they ask you about the scar, and they'll buy it. The one I just told was the true one, though.
6. Glass containers are fragile from the inside.

Anyway, that's my "nitric acid acts upon trousers" moment.

4 different valuable observations, science gained a lot that day.

My dad used to be a police officer in South Africa. He had several interesting artifacts from his time there.

One such artifact was an unmarked black cylinder with a spray nozzle. One day after school, I had managed to get locked out of one section of the house and could only get into the kitchen and my dad's office. (Houses in SA often have security gates inside locking off sections of the house.)

It was sitting in this office, waiting for someone else to get home and let me in that I absent mindedly started playing with this cylinder. I sprayed a small bit out. It made made a really cool heat haze effect in the air. Awesome, but what the fuck was this stuff? Well I'd just had a highschool science lesson on how to test an unknown gas... you waft it towards yourself, you do not sniff it directly. So I sprayed out a bit more and wafted it carefully towards my face...

Instant regret. My nose felt like I'd just done a netti pot of hot sauce. Eyes streaming, snot dripping.

Lesson 1 learned. Don't play with random cylinders of mysterious chemicals.

I found out later that it was tear gas.

Hey pop quiz: What's the worst thing you can do if you get tear gassed?

That's correct! My dumb ass ran straight for the kitchen tap. Lesson 2. DO NOT USE WATER to clean off tear gas. I will say that I knew IMMEDIATELY that I had fucked up a second time. Felt like my entire face was on fire. Baaaad times!

Mmmm not the same , but similar.

My single mother was changing a headlight in our garage. Like any poor person worth her salt, my mother was using a butter knife because we didn't have proper tools. I wanted to see what would happen if i crossed the cars battery terminals with the butter knife. I decided to make it look like an accident. I "bumped" the butter knife and it locked into place across the terminals. Sparks shot from both ends when it made contact. From the center out the butter knife started glowing red from the heat. It all happened so fast, i smacked the butter knife free with my right hand. 30 years later I still have the physical scar across my middle finger, and the emotional scars of what she called me (admittedly deserved).

It gets quite hot but only makes nitrocellulose (aka guncotton) reliably with unbleached cotton, which you rarely find in clothes.

I once decided to see what would happen if I connected the terminals of a 6v lantern battery with an unbent paperclip. Turns out it glows red hot and hurts like a motherfucker when you grab it in a panic to disconnect it.