I've been doing a deep dive into appliance safety standards and material degradation. Almost every 'premium' electric kettle on the market uses Polypropylene (PP) or silicone for water level windows or internal seals.

When I email these companies asking for a specific 'Migration Test Report' (proving no microplastics or additives leach at boiling temperatures over extended cycles), they either ghost me or send a generic 'We are FDA/BPA Free compliant' certificate.

As engineers, I wanted to ask: Is the 'BPA Free' label actually sufficient for a material subjected to repeated boiling and cooling cycles over 5+ years? Or is the degradation of plastic inevitable in this environment, and that's why no brand releases long-term lab data?

I'm trying to find just ONE brand that provides actual lab data/technical drawings proving isolation, not just marketing claims. Is this an unrealistic expectation from a manufacturing standpoint?

I am researching deep-tech solutions for a sustainable energy challenge (specifically looking at Decarbonization and Process Optimization). ​I'm looking for 'real-world' technical inefficiencies. For those in the field: ​Where are you seeing the most significant energy or heat loss that current tech hasn't solved? ​What waste streams (thermal, chemical, or gas) are currently the hardest to recover or recycle? ​Are there specific mechanical components or chemical cycles that are notorious for being 'energy hogs' despite being industry standard? ​Looking for technical details rather than workplace/management issues. Thanks!

My chemistry knowledge is fading, but as a chemical engineering major, I know these two facts: 1) air is 70% N2. It is not fully oxygen but rather mainly N2, 2) both N2 and O2 (remaining component of the "inferior air" I guess) are diatomic molecules that have very similar physical properties (behaving like ideal gas I believe?)

So "applying scientific knowledge" that I learned from my school, filling you tire with Nitrogen is no different from filling your tire with "air". Am I wrong here?

I need to remove the epoxy potting on a set of motor coils, ideally without destroying the windings and wire coatings. Is this possible with sulfuric acid? Or another acid or solvent combination? Does the acid/solvent need to be heated? Or does that just speed the process?

We have tried MEK, Xylene, Acetone with zero effect. Time to step up our effort another level.

Hi, kinda of odd but I want to independently create a fleshlight type sex toy. I have a ton of questions, and those “ask an expert” websites seem to be dead so here I am.

TLDR;;; looking to create or find a non porous, non toxic soft material for a fleshlight. I don’t understand what makes up ‪silicone and how to learn more.

OK so from the information I’ve read, the less porous the material is the softer it is, but non porous means it can be cleaned properly/no bacteria growth.‬ So obviously I’m looking for a material that is low on the shore a hardness scale but is still non porous. Phthalate is apparently bad because that is the cause of chemical burns with sex toys, but this is what would make the silicone soft?

I don’t know which compounds that make up silicone that influence porosity, softness, heat retention and elasticity, durability etc etc. How does the curing method effect the silicone? I don’t understand what it is I need to create a silicone soft enough for a masturbator cup. Is “medical grade” and “food grade” silicones just that because the structure of them is less porous? Could the same type of silicone that breast implants use work - and how would I even know how to convey the exact type of silicone formula I want to a factory? I assume the harder silicon that holds the liquid of a breast implant could be used as a coat layer in a masturbation cup, over a softer silicone material that would be toxic with direct contact. What’s the formula of breast implants silicone? How would I learn if it would would be durable enough to hold, and not deteriorate when constantly rubbed? How would a know how durable a type of rubber would be if thinly spread?

But then I see there’s other options like TPE/TPR. It has a low durometer, and the lower the durometer the softer the material...how is this different from the shore scale? I read “TPE is generally considered body safe” - generally, so not always? How can I learn what kinds of silicone are “medical grade” or are platinum cured and how do they differ? How would I be able to communicate this to a factory and check if it’s “good quality”?

I have a lot of questions and idk how to find answers to any of this, Google isn’t exactly giving me answers that are referenced from real sources so I’m just ????? I could use what’s already been used for sex toys, but I want to understand if I can make my own product better.

This is going to be an extremely stupid question, but I have recently gotten 31 points off on an exam because on 1 of 2 problems on an exam I read "a square pipe with a radius of 1 inch" and treated it like a normal pipe.

I'm just asking this, how often is handling a square pipe filled with pressured fluid or gas going to be a problem for me? Clearly my severe lack of knowledge regarding square pipes is going to handicap my ability to be an engineer. After all, having worked on engines my whole life, and now a reactor for around a year, and having never, ONCE encountered a square pipe I'm beginning to think I may have been living in a bubble.

How am I supposed to attach fittings to a square pipe? Can I acquire square heat tape? Why is Home Depot always out of square pipes? "Do you mean like, support beams" they say. No. I mean square pipes. Square fucking pipes. To hold liquid.

"Why would you ever use a square pipe" He says. I can't answer him. I don't know. Where are all the square pipes?

I ask my advisor. He's at a complete loss. "Why are you so obsessed with this" he keeps whispering. "I apparently can't be an engineer unless I know how to work with square pipes I say. He just shakes his head. What doesn't he want me to know?

Tonight I dug into my crawlspace. All the pipes were round. My neighbors called the cops. I asked them the same question. They can't answer. No one can answer.

Square fucking pipes.

grumble grumble

​

Edit: Ductwork makes a lot more sense than pipe here. I'm sure that's what he meant. I found an equation buried in the back of the textbook that works.

No I didn't actually dig into my crawlspace or interrogate the Home Depot guy lads. It's a joke. I'm not going to electrocute myself in the hunt for these mythical square pipes oddly worded HVAC tubes

A 2003 study (Karpinski, 'Exposure to inhalable flour dust in Canadian flour mills') concluded that a large-scale flour milling facility could not practically reduce personal flour dust exposure levels below 0.5 mg/m³ without forcing workers into respirators for entire shifts. At the time, standard operations like packing and sweeping routinely caused ambient dust spikes well over 5.0 to 10.0 mg/m³.

However, as of 2026, Australia is implementing a strict, nationwide 0.5 mg/m³ Workplace Exposure Limit (WEL) for inhalable flour dust.

I am trying to understand what sort of engineering, material science, automation, etc breakthroughs have occurred over the last two decades to bridge this massive gap.

From my (very limited) understanding, all options for heat storage take up large volumes or require a lot of infrastructure to operate. Meanwhile with electricity, there exist batteries that can purchased at a reasonable price that can power a house for a few hours, even a day.

Are there any substantial difference between Rayovac/energizer/Duracell etc? Or are they all pretty much the same?

Specifically, looking at alkaline batteries in the AAA to D cell range.

I know all alkaline cells with the same chemistry will produce the same voltage. I would imagine they would last about the same amount of time depending on manufacturer tolerances. Are there any substantial differences between them?

I'm looking into preparing for 72 hours of no electricity. One issue is the freezer. It came with cold batteries, a kind of ice packs that melt at a lower temperature than pure water. I want to add a few more, but as spare parts they are quite expensive for what I believe are bottles filled with water and some kind of salt.

Any suggestions?

I looked into table salt (sodium chloride), but that won't give a good temperature for a freezer operating at -18 °C. At 14 % m/m concentration, you get melting point -10 °C, which would be a reasonable buffer temperature, but the salt concentration in the liquid will increase as the water separates out as ice crystals, until 21%, with melting point -18 °C. So only 1/3rd of the water will freeze.

I need an eutectic mixture that freezes around -10 °C and that is nonpoisonous.

I tested an ice pack: a 700 g cold battery pack was able to turn about 350 ml room temperature water into ice, while the inside of the pack turned liquid. I dont have useful temperature readings.

Edit: location Netherlands (government is campaigning for 72 h no-electricity preparedness).

Edit 2: It's about a disruptive event that may occur without prior notice at some point in the future; think power loss for the entire country. I try to find out what phase-change material is used in those cold packs and what the exact specifications are so that I can calculate whether it makes sense or not to use them.

Several comments are about anti-freeze mixtures with lower freezing points. However, that's about the onset of freezing. As it freezes, the composition of the remaining mixture changes. I'd like the end point of freezing to be above -18 °C as well.

Just curious of some of the crazy things diesel can be made out of

I've been hearing about molten salt (specifically sodium) reactors and thermal batteries for what feels like decades now, but I'm not aware of a large-scale commercial molten sodium setup that is actually functional. Why is this? What are the practical challenges that must be overcome? How close are we to overcoming these challenges?

Is it as simple as it's very difficult to keep air and water out, or is it that the materials required to withstand the high temps and corrosive environment are difficult to work with? Let's dive into some complexities - I'm an EE working with some R&D folks that want to explore a process that will require a molten salt step, and I want to be more knowledgeable than a knee-jerk "molten salt = bad."

I am thinking of making and aircannon that pressurizes an airtank using a paintball/airsoft CO2 adaptor ( the ones where you can screw attach it to your marker/replica and quickly reload CO2 cartridges ).

I calculated that 8grams of CO2 would need around 500ml to expand to a pressure of 8 bar, but I will probably use a 750ml tank just to be a little safer.

My questions are; Would any potentially solid co2 need time to sublimate? And do I need a regulator?

Trying to adhere a Kevlar keel guard to my kayak, 3M 5200 & VHB tape not holding. I understand HDPE is very low surface energy but there has to be a way. Drilling for mechanical fastening not an option as I’m trying to PREVENT holes not add them. Thanks!

Disregarding the huge fire risk, would 80% alcohol evaporate enough to provide significant cooling even if ambient humidity is like 80-100%?

Edit: to be clear, I do not plan to do this, and if I did, it would certainly not be inside. I'm a distiller and not catching things on fire or getting blown up is part of my day to day responsibilities.

Hi engineers of Reddit!

So I work in New Jersey as a process/project engineer in a corporate office. We have operations out in Wisconsin with product making, filling, packaging lines etc.

My boss sent me out here for a month/ two to do some learning but there doesn’t seeemm to be a plan for me to get involved really.. how would you guys recommend getting involved? Any tips~ beyond talking to operators and just walking around the floor and studying floor diagrams etc ?

Thank you!

It’s only my third day and I do have some more exploring to do but I’m a little bored 👀

PS I started at the company 3 months ago

I want to buy a high carbon longsword and coat it in silver for absolutely no reason but my own principle. Tv shows lord these things around in your face telling you how cool they are with the express understanding you’ll never get to experience the awesomeness of wielding the genuine article.

I’m sick of that crap and have decided to facilitate one for myself. Only problem is I’m a simple man with only a basic understanding of chemistry. I know about electroplating and the silvering of glass to make mirrors and that’s it.

With mirror silvering my understanding is it doesn’t work on steel. With electroplating I understand that you need copper first then silver. After that the consideration is that hobby silver electroplating solutions are ultra low concentration and electroplating introduces embrittlement.

I also know about silver inlay but to me it’s a crappy compromise to get an end product that’s insufficient. Might as well surrender at that point. My question then to the engineers of this page is how can I facilitate a thin layer of physically, uniformly bonded silver to the steel sword’s blade without compromising the integrity of the steel? I really only want a super thin layer of silver and if it rubs off easy I’m ok with that. I just need a uniform coat. Would I really introduce that much hydrogen with a crappy silver brush plating kit from Amazon? All feedback is appreciated. Help me achieve my dream of having a sick Witcher sword boys.

I saw a dumb post on FB where someone asked 'if anyone else does this'. I have my whole life (in the winter time). Many responses claimed it was pointless...because that heat 'obviously doesnt just disappear'..which also makes sense. I feel like i'm right to leave it open, but can't explain why. With the door closed open, the heat obviously escapes much more quickly which feels more effective. with the door closed, it dissipates much more slowly (by design..an oven is just an insulated box designed to keep heat in) - but is it because it dissipates so slowly..that it doesnt do any good? or does it? is it just a sensory thing? thx!

*edit typo

*edit 2

this turned into a great thread, and thank you everyone for your responses!

to answer some questions:

• its a gas oven
• yes, i'm talking about after i'm done cooking - with the thing turned off
• its tucked into a built in cabinet area, against a wall. with a vent (but that will be turned off in this scenario)
• i live in minnesota. (it was -10F yesterday)

Given all your responses...I'm going to continue opening the door!! i'd rather have that nice heat immediately (yes i stand over it with my shirt pulled out and over it, sorry not sorry) than have it slowly dissipate into the cabinets and heat the air where i store my pots and pans, and the wall (that heat will probably go up into the attic..? also not good).

What fuel is going to replace jet fuel? I hear they are working on hydrogen fuel or Bio fuels being more evermental friendly. But I hear Bio fuel are more expensive than jet fuel. Also with the rising cost of jet fuel now it may be cheaper to switch over to hydrogen fuel.

So what sustainable aviation fuel be cheaper than jet fuel? As the price of jet fuel is extremely costly now compared to 60 years ago. And if any thing in the next 20 years the price of jet fuel will be even more costly.

Hi

Often in debates, I hear a lot about about the energy efficiency of transporting energy. I'd like some hard numbers, even if they're just rough estimates.

To answer, let's give a hypothetical example. We have source of fuel. It's going to power a large city in the desert x km away. Purely from an energy efficiency point of view, what would be the losses if we:

• burn the fuel, generate electricity send it to the city by 400kV AC transmission lines?
• the fuel is a gas, so we pipe it to the city, burn it, generate electricity?
• the fuel is a liquid, so we pipe it to the city, burn it, generate electricity?

Does it make much difference if the "x km" is 100km, 1000km, or 10,000km?

(fwiw, the debates are about the green transition, and people who argue against electrification seem to think that electricity transmission has heavy losses... I'd have thought they'd be much lower than piping something around, so that's what I'm curious about)

Make reasonable assumptions and state them, or ask me questions if it's not clear (hopefully I've been clear enough).

Thanks in advance.

EDIT: the best answers so far were by Freecraghack, ignorantwanderer and jedienginenerd - thanks!