Ambient Temperature for 3D Printing

We’d been discussing mercury actually (with me having a giggle about how it used to be used as a cure for VD). I used Cr6 as an example of bad science, not as something to derail the thread because it was raised as part of the discussion.

Did I ever suggest otherwise? Or were you attempting to build a straw man?

Sarcasm is unbecoming as is copying huge lumps of Wikipedia without citation or quotes. We used to call this plagiarism but my college days are a fading memory.

You clearly don’t like science that doesn’t agree with you. Here’s a simple article for everyday people run in a nasty little British tabloid that’s rarely pro environment, being that it’s only slightly less right-wing than Donald Trump.

Was Erin Brockovich, the single mother who claimed her town’s water was poisoned wrong? | Daily Mail Online

The facts (and remember level of Cr6 was above “safe” limit then) speak volumes. I don’t choose to believe red or blue, I’m a science writer (retired) and I’m interested in facts. The facts behind this article come from a professor of epidemiology and once again, show that Brockovich was full of it.

Some chemicals get a bad name and when people follow what they believe (usually the people with the flash website who speak in hyperbole) then that becomes fact.

Aluminium salts are also in the frame for a number of ailments and yet the evidence to back that up is suspect at best. Much of that derives from a terrible incident in Camelford, Southern England when tons of aluminium sulfate was dumped into drinking water, resulting in a level 3000 times that considered safe and people got sick. At least one lady died and aluminum was found in her brain matter. The details are really O/T here but you’re welcome to read up and cross-reference scaremongering sites, there are plenty of them.

The point here is that when we focus on the wrong compound, bad or misleading statistics, or just close our minds to new evidence, we miss what is right under our nose. Blaming glyphosate (and GM tech) for cancer and god knows what else in the tobacco regions of Argentina masks the real environmental catastrophe where the poor are ingesting toxic amounts of heavy metals in their drinking water. But it was easier for a documentary crew to blame Monsanto/Bayer and give those people the idea that they would make enough money to get themselves out of crushing poverty caused by American tobacco buyers like Philip Morris.

And children continue to suffer there for that very reason. The insidious nature of lead (Pb) in particular means this won’t go away if the lead is removed from the water supply either. You might read from that, I have very little truck with people who look to prove their own ideas and ignore contrarian evidence that is presented. Remember what Richard Feynman said.

Various (and very vocal) voices have claimed that glyphosate causes cancer (based on sketchy evidence and bad science) and then went on to point out there are “detectable” levels even in organic wines.

That glyphosate is present at such levels is questionable since the assays were based on unpublished techniques but they found what they were looking for. Not that it mattered, the outcry was as sudden as it was loud.

But there’s a far more insidious toxin/carcinogen in wine. Alcohol. And it’s present at far greater levels than glyphosate. Ethanol causes cancers through the entire digestive tract, it’s toxic to our liver and brain and is fetotoxic too even in relatively small amounts.

Yet save for prohibition, there hasn’t been any serious attempted to limit alcohol consumption in the US; nor pretty much anywhere in most of the West. That’s one thing Muslim countries do have right.

To quote you, “opinions are not facts”.

It seems (and I could be wrong) that you’re finding articles that agree with your own belief but not following or even reading them.

This is a natural mistake we’re all prone to called “selection bias”.

The Livescience piece which isn’t written by a science writer and quotes from the EWG, an advocacy group known for playing fast and lose with the facts. In this case, apparently conflating environmental Cr6 with Cr3 - but it’s all chromium to them, just like ethyl mercury and methylmercury are mercury compounds. One is used in vaccines, one is a dangerous environmental pollutant. Antivaxxers don’t know the difference either but it matters.

Cr6 in the tiny (but detectable) amounts in drinking water is destroyed before it can ever get into our systems.

This is a fact. It’s not my opinion, it’s backed up not just by multiple respected doctoral level chemists but supported by the evidence from Hinkley as discussed in that article about Brockovich and it’s not the only one. Here’s another that’s light on technical terms but sources actual indentured scientists from respected universities,

EWG and Erin Brockovich recycle discredited chromium claims – Food Science Institute

Copypasta is a term I use when people copy and paste something from a source without attribution in an attempt to make themselves appear more learned or invested in the subject. It’s also become a form of spamming depending on how they are used.

This is a quote from the EPA source you’ve cited above and (again) it agrees with the science that Cr6 in the levels we’re exposed to is safe and might even be beneficial. Emphasis is mine.

“Chromium-3 is an essential human dietary element. It is found in many vegetables, fruits, meats, grains, and yeast. Chromium-6 occurs naturally in the environment from the erosion of natural chromium deposits. It can also be produced by industrial processes. There are demonstrated instances of chromium being released to the environment by leakage, poor storage, or inadequate industrial waste disposal practices.”

Now there’s an irony here that Professor Morgan might have accidentally unearthed too. His analysis of the data shows that the rates of cancer in Hinkley (contrary to my memory) are not the same but actually LOWER than the average. Which might suggest that a miniscule amount of Cr6 in water, which results in Cr3 the essential element in our diet when it hits the stomach, might actually prevent some cancers.

I wouldn’t bet on it. The sample size is far too small.

But Brockovich tried the Hinkley play again more recently only this time a judge demanded to see the data and threw the case out. In fact, she seems to show up every time there’s a $$$ to be made only to sublimate when it becomes clear there isn’t, leaving people in these areas rudderless. Brockovich and those lawyers aren’t just hurting the people they claim to want to help, but they leave a tidal wave of bad science in their wake which then gets amplified by social media and on the Internet. Why? Because people feel let down (who wouldn’t) but they tend to believe the honeyed words and let’s be honest, science isn’t easy.

As a writer I have to rely on my sources, but I can evaluate them coldly and without emotion even when they don’t agree with what I believe. Because if what I believe is wrong, then I’m wrong. Like a butterfly, I can flit between the various specialties and learn from each one forming a view that is supported and informed by evidence.

There are other sources in that Mail article that prove what I’ve been trying to say - people far more educated in this subject than I am and people without an axe to grind.

Here’s Dr. Henry Miller, MD (full disclosure, we know each other, but we’re not colleagues) Don’t buy into the chromium-6 hysteria :: Henry I. Miller M.D. (henrymillermd.org)

And here’s Dr. Joe from McGill University explaining this in more detail at Quackwatch:

Erin Brockovich Story Largely Fiction

and Michael Fuemento (retrieved from the Internet archive):

Bestselling author Michael Fumento reports: “The Dark Side of Erin Brockovich.”

The experts say one thing but people tend to believe the Hollywood fiction which is then amplified by scaremongering self-interest groups like the EWG, another one whining about glyphosate in wines but seemingly unconcerned about the real carcinogen in there.

Even the “woke” Californians with Prop. 65 don’t seem overly concerned about alcohol, but that legislation which was well meant has given groups not limited to the EWG a plentiful supply of extra-large cudgels to beat us all with.

Back with 3D printing, much the same applies there too. People are scared that their hot ends will autoignite PLA and burn the house down and yet seem oblivious that poor quality power supplies and badly routed wiring are the real culprits. Because it’s easier to blame what you can see and touch rather than the thing you can’t. Bad or worn wiring, the most frequent cause of these fires is hard to see.

This is a little outside of my area Bob, but I can tell you what I know which isn’t much and in many ways isn’t definitive, so do take this with a grain of salt! I hope @Ender5r can jump in and correct anything I’ve misrepresented, they seem to have a better handle on chemistry than I do.

PTFE:

I don’t have my birds any more - and that might have accidentally gone to demonstrate (if cruelly) the risks.

Birds have a very different respiratory system to us as they have evolved to burn energy at an enormous rate to power the muscles required for flight. Where mammals have a tidal system (we inhale and exhale, with gas exchange occurring during that process) birds have a one-way process where gas exchange occurs not just in the lungs, but even through their hollow bones. Where our lungs are a dead end street (so to speak) birds have a freeway.

It’s a little more complex than that (penguins, for example, don’t share the same respiratory system as modern songbirds) but that will suffice for this discussion.

Even when not in flight, birds are still absorbing gases much more quickly than we are and because of their small blood volume compared to a full-grown “hooman” little songbirds like canaries and finches will succumb to gaseous or particulate air pollutants much more rapidly than we do. The dose makes the poison as the old guys used to say.

Mammals are susceptible to certain atmospheric pollutants because of our tidal respiration though. Diesel particulates are highly carcinogenic and by their nature, can get lodged in our alveoli (the little sacks where gas exchange takes place) and cause neoplastic growths: lung cancer. Birds are probably less susceptible since the gas never really “rests” but rather passes over the tissues due to the Coanda effect.

The manufactuer of Capricon tubing has some interesting analsysis with some citations about birds and more here: Safety

A similar process results in smoker’s lung over many years with the alevoli gradually filling with tar. Lovely! Our bodies have a system of tiny hairs (cillia) to remove foreign particles but smoking paralyzes them - another reason why smokers are more likely to suffer with a variety of particulate-based lung diseases than non-smokers. (You can see where I’m going with this I’m sure.)

So the good news is if you’re not a bird, you’re not going to suddlenly drop dead from a florine-compound neurotoxin - at least not suddenly.

Florine compounds occur widely in nature but as with the EWG, there are SIGs that have found a nice way to extort money from the ignorant by claiming all manner of hellfire and brimstone.

It’s this reactivity that sees it bound up into compounds and not just hanging around in the air. It’s slightly less reactive cousin, chlorine is similarly usually found bound with sodium to form table salt.

That’s not to say that florine is safe - it’s one of the most reactive elements in the universe, matched only by a woke millenial when someone points out how environmentally unfriendly their salt lamp actually is… (Mining pink salt for lamps is usually done by children who are exposed to crushing temperatures and are forced to breath iron-infused salt particles which in turn damage their lungs.)

So that segue is on topic.

PTFE is very safe when used according to manufactuer’s directions and that’s the key point here.

Teflon flu - the informal name for the symptoms we exhibit when exposed to PTFE under extreme heat is acute and usually resolves quite quickly. Symptoms are flu-like with blood samples demonstrating a increased auto-immune response. Chronically, no reputable studies that I’ve come across have found any link to cancer via the respiratory route. Welders and other workers have in the past sufered with a similar, “metal fume fever” but this is less prevalent now as standards, not to mention information, improve.

Of course, if you do a google, you’ll find any number of apocolyptic pages and even websites dedicated to this subject and floride compounds in general. Water floridation is commonly cited, but people exposed to it have much lower incidences of dental caries which means they are exposed to far less dental work. Dental caries (if left to progress) can also result in death through septicemia as bacteria from the cavity get into our blood directly. It’s a case of the lesser of two evils…

Perfluorooctanoic acid (PFOA) which is used in the creation of PTFE is the risky one but as I’ve mentioned in that long screed about Cr6, it’s HOW it gets into your body that matters. PFOA has been found in drinking water and that’s the most likely route into our bodies. This substance is being phased out as (and this is no comfort to Gen Xers like me) we could ingest it simply by consuming products cooked in Teflon-coated pans.

As I recall, 3M was sued over the danger of its (original) Scotchguard which is a related chemical, PFOSA. It’s a persistent organic pollutant too and really not the sort of stuff you want to be around.

Right now the IARC seems to consider these products as likely carcinogenic candidates (2B) but the IARC (much to the chagrin of many scientists) assesses HAZARD and not statistical risk. Just because someting can cause cancer doesn’t mean it necessarily will. This is a fact lost on many, but not lawyers who make a living relying on that simple ignorance.

Worker safety concerns everyone, but pyrolysis of PTFE , for most of us, should be a minimal concern since (again, so far as I able to find to date) there are no recorded incidencts of people actually suffering lasting harm from these fumes. The danger is likey at temps 400C and higher where perfluoroisobutene is produced. Now while interested parties might start carping about how toxic it is (and it IS Bob, it is) PTFE pans have been around for many decades and by simple numbers we can intuit that many a housewife or careless husband (waves hand) has let a PTFE pan burn until the place was filled with smoke.

The most serious danger from a teflon frying pan is more from the wife when she gets home from bingo and beats you senseless with the pan because you burned all the “non-stick” off.

Joking aside, as I mentioned about glyphosate earlier, just because it’s relatively harmless, doesn’t mean you should go out of you way to set fire to it and take huge lungfuls of the smoke. It’s not an incense (and those too can be harmful if not used with care).

(cntd.)

Nanoparticles

Your other question regards nanoparticles and the short answer is I don’t know (no one does for sure, yet) so some of this is speculation. Anyone who claims to know is probably misguided, lying or more frequently got something to sell you. Yes Dr. Mercola, I’m looking at you.

As Dunning & Kruger pointed out, a little bit of knowledge makes us think we know more than we do. Even though such a fact has been known since antiquity, but hey-ho.

Nanoparticles are just tiny particles that we’re only recently starting to be able to see. Many complex molecules are nanoparticles in isolation because it refers to an individual unit of a substance measuring between 1 and 100 nM (that’s really, really small but not as small as a large atom). We can’t see them with optical microscopes because they measure less than the wavelengths of visible light.

So what we’re really talking about is something that most of us would consider a gas and the two aren’t really that dissimilar. Visble smoke, for example, is a large cloud of particles that measure more than a wavelength of light (micro particles) so they disturb the light and we can see them.

The insidious-sounding name “nanoparticles” hides their true nature to some degree: we’re breathing the damn things all the time and our lungs have evolved with them so most (the ones that occur in nature) can generally be regarded as harmless because most are too large to enter through the lung tissue and most plastics are not water soluble (PVA - sometimes called Elmer’s or woodworking Glue - being a notable exception here).

Man-made nanoparticles are more of a concern but until we know more about them, the best we can do is tread carefully. I don’t know (as I’ve said, this is outside of my field) but I suspect that pyrolysis of PTFE creates what would be termed nano-particles since these chemicals are quite large molecular chains. (Poly- meaning many remember). There are many thousands of nanoparticles but unless stated otherwise, I’m talking about those produced by plastics we use in 3D printing.

Now refer back to what I mentioned about Teflon flu. Note that in cases where this has been noted by medics, blood samples have returned with an increase in the number of white blood cells. Not only that but patients recover after a few days of bed rest.

This strongly suggests to my limited understanding that unless the chemical has some way to enter our cells and cause damage through some hitherto undiscovered mechanistic action, our own immune and detoxifcation systems will come to the rescue as they have been doing from the moment we were born. It’s likely they leave the body via the kidneys within a few days of exposure as (so far as I’m aware) we’re unable to break such chemical down.

The sheer size of these particles may, in fact, be what protects us from them. My celluar biology is a little hazy now, but as I recall, one of the reasons we have to digest food is to split it into much smaller pieces: simpler, smaller molecules which can pass through the cell wall.

This suggests to me that although they might well be detectable in blood and urine (because they’ve entered through the lungs and directly entered the plasma) they are unable to do any actual cellular damage.

This isn’t the entire story of course, and I would defer to world’s experts hired by the CDC, EPA and other agencies rather than some dude on the Internet. What I can tell you is that I don’t have dog in the race other than a concern for the health of my team and those people I’ve worked with.

As I tell my kiddos: "Be informed and careful, not ignorant and fearful. Use ventilation and don’t go sniffing the fumes!

I would like to suggest we table the OT discussion & get back to 3D printing issues. We may differ on many other issues but I think 3D printing is 1 we can all agree on.

Agreed @Ender5r It’s a shame that a little bit of brevity way back up the thread triggered such a polarized response.

To be fair to @bobstro he was asking a question directly related to safety surrounding PTFE (not necessarily the environmental issues) and the nanoparticulates that are produced during 3D printing. There is a lot of confusion around how dangerous PFTE is when it’s heated beyond the level it’s designed to withstand. Capricon itself doesn’t make any claims about increased temperature resilience but I have seen mention of it elsewhere. The only thing I’m able to determine from Capricorn is they use a much more accurate production process so there is less “slop” inside the tube, resulting in less backlash and presumably that would lead to shorter retractions on machines like the Ender 5 which has fairly lengthy Bowden tube; presumably this applies too all CoreXY designs? My model came with Capricorn as standard. The reason I landed here in the first place was because I was discussing the heat/fire issue with out wonderful host over on YouTube and he suggested I brought it here.

There’s a lot of twaddle all over the Internet regarding the safety (or lack thereof) of various 3D filaments, particularly as there are so many of them in a bewildering array of colors and formulations. Personally, I tend to stick with what I know: PETG when I need the extra strength or heat resistance and PLA for convenience. I have upgraded my TronXY with a direct drive extruder based on a Thingiverse design but then I found myself asking, “did you really need to do that?” because I’m not really in the market for Ninjaflex or something similar so apart from being an interesting exercise in design since I had to covert from a triangulated STL to an ngon .blend and then work from there.

I’ve updated my digital thermometer design to handle two independent temperature sensors but it’s not production ready because I’ve been derailed by family issues. Even then, two sensors seems like overkill unless one was outside the cabinet? The DHT 22 sensor it uses measures temperature and humidity (not massively accurately, but fine for what we’re doing).

Since we’re back on track, I was wondering that in the case of a ventilation system, @roon4660 suggested a wax-based greenhouse lifter (clever stuff those) but that has the potential to be a bit slow. I’m waiting to hear from a major manufacturer regarding activation times, etc. but I rather like the idea of using a louver - total overkill of course, but how utterly cool (cough) would that look? Sure, we could do that electronically too with stepper motor and gears, etc. but can you imagine how magical it must look to see what appears to the uninitiated to be something working without using any electricity at all! Now that is elegance from simplicity.

Using an MCU like an Arduino is rather boring by comparison but it does raise another couple of potentially interesting features that aren’t possible with wax-and-pistons.

  1. First of all, we don’t have to drive the heat out of the top and bring cool air in from the bottom, although this would be the way I think I’d do it. But by placing the blower at the top and forcing air down, rather than pulling it up with the natural flow of warm gas, we would push some warm air away from the heated bed, thus (perhaps) compensating for the iffy design of the Ender 3 and clone hot end designs.

  2. Hotstuff (out of the box) charts humidity and temperature so it’s possible to keep an eye on what’s going on inside the cabinet. This might be useful to see how effective a cabinet design is, but again, this might be overkill.

  3. Hotstuff (At Mega 328p) is probably totally over the top for such a simple application, particularly as all we’re doing is varying the rate of a fan from 0 to full-tilt based on the temperature presented by a sensor. I think the ATTiny would probably suffice quite nicely (although I haven’t run a test as yet) because all we’re doing is adjust in the pulse-width of a PWM to drive a simple computer fan based on the input from a sensor. DHT22s have a one-wire interface and directly report the measured temperature to the MCU. Something as simple as this wouldn’t even need a circuit board or even a timing crystal (speed isn’t vital here, the DHT22 reports every 2 seconds give or take) and IIRC it can produce a PWM output which could easily drive a small jellybean “power” Mosfet to regulate the fan speed. It’s even possible to do this discretely but that requires calibration which is a bit of a nuisance and no one ain’t got time for dat.

  4. I looked at solid state “smoke” detectors but as I think I already said, I wouldn’t trust my life to one! A cheap battery-powered one is less than $10 these days and they emit a piercing cry that even the dead would have trouble sleeping through. I have a couple of alternative air quality meters here (well, when I say “meter” I should really say, detectors) but I wouldn’t trust them in any mission critical application. (I once re-designed a patented industrial “safety” system when it became clear that the original designers had made it from a spec. sheet and had never actually put their theories to the test. As it happened the original design was already fail-safe, just a bit too trigger-happy, but that’s drifting O/T.)

Why use a time-tested mechanical solution when you can use an over-engineered IoT device? If you’re not controlling via at least one microcontroller and MQTT, you’re doing it wrong. I wouldn’t consider the design complete without an OctoPrint plugin with full touch GUI interface. Then you need the robotic arm to flip the light switch…

Don’t forget the thorium micro-reactor to power the robotic arm ?

HAHA! I like it

Well, as I’ve said before, there are potential drawbacks to the wax and piston approach, if we remove cost which is fairly negligible even if already have the bits.

The wax and piston mechanism converts heat into kinetic energy - pretty basic physics. But the response time is something and gradient of the hysteresis that rather intrigues me. Obviously (I hope this is obvious!) it’s not necessary for the unit to open full in order for some heat to escape but there is a question of how hot it could get in the cabinet while the metals and waxes get sufficiently warm or the window to open and begin to vent air.

That would rather defeat the object of having a ventilated cabinet if the temperature rose too high OR conversely, too much heat was lost as the wax and piston closed back down.

I’m not eschewing this idea, I still think it’s beautiful suggestion, but I question if the small amount of heat that’s generated (in real terms) can be matched to an existing greenhouse opening solution. Greenhouses get very hot, very quickly - just like cars. Which is why you should never leave your mother-in-law in one on a hot day. I’ll never live that one down as long as I live.

The IR energy from the sun even beating on a small car, I mean greenhouse, is not insignificant even on an overcast day. Give or take, it’s about 1,000 watts per square meter.

Anyone want to punt some figures for a typical printer? (Asking because I don’t know). I’m feeling pretty crummy right now but right off the top of my head on the back of my last clean tissue, the E3 bed heater is about 0.4 square meters at about 50w and the hot end would add about what 20-30? A bigger machine would produce more of course, but anyone who can afford to run a 1 kw 3D printer isn’t going to worry about a putting a box around it to save a few bucks.

The sun isn’t just coming in through a single 1 M^2 window, it’s beating down over the whole structure - so you can see why things get so hot, so fast. This means there’s plenty of latent heat for the wax and piston to get nice ‘n’ 'ot and open with some haste.

This is just a wild estimate based on some figures I pulled out of my Thorium-powered Flux capacitor (see, I am paying attention and that made me LOL) but you can perhaps see why I’m suspicious as to the efficacy of such a solution.

However, I’m the first to admit when I’m wrong and I prefer simple solutions because if you saw my last patent application it was written in such a way that I couldn’t understand it and I designed the damn thing!

==== And now for some completely unnecessary levity ====

Why does it take a big man to admit that he’s wrong? Because who’s honestly going to go up to him afterwards, poke him in the chest and declare, “See! We told you so!”

I will try to stay on topic but I feel compelled to provide links for science and skeptical thinking:

https://www.skeptic.com/

Do activated carbon filters increase the safety of resin and other materials printers? Which resins are the safest?

This is STILL off topic, which is detailed in the thread title and widely discussed over a number of posts. I’ll keep the first part on topic and include a little more science for those interested before I indulge you again.

We’re discussing the merits of active and passive methods for controlling a micro-environmental temperature inside an printer enclosure. I’ll remind you that one author mentioned that although the E3DV6 head is designed to operate at ambient temperatures up to 40C, there are parts of the world where ambient (room) temperatures can exceed that.

I’m personally of the opinion that while the wax-and-piston method is an aesthetically pleasing and reliable method where there is a large heat mass (the sun beating down 1 Kw per M[SUP]2[/SUP]) on a greenhouse, there doesn’t appear to be sufficient energy in a typical 3D printer producing perhaps at best 150 W across around 0.5 M[SUP]2[/SUP].

One of the reason why thermistors (and similar devices) are small and/or enclosed in a highly conductive material is to ensure they are rapidly responsive to even minute changes in the temperature of the material they’re measuring. An easy way to understand this is to boil a kettle full of water and time how long it takes, then put just enough water in to cover the heating element and run the same timing. The energy entering the system (mostly from the heating element) doesn’t change, only the mass of material that’s being heated.

The thermal mass of a thermistor is negligible compared to a wax-and-piston mover such as might be used to open the window on a greenhouse and it’s this factor that directly affects their ability to operate in different applications. All that said, I could be wrong. The only way to be 100% sure would be to design an experiment to put that to the test.

I’ve already re-designed something I created last year to included this and I’ll probably publish a complete guide later this week (on Instructibles or Hackaday).

It won’t cool an E3DV6 head down below the ambient temperature of the forced air though - that’s a case of needing a better head.

As promised, I’ll now deal with your “query” which frankly comes across as rather impertinent.

If you want to know about activate charcoal filters or fume hoods, then you really should start a thread about that. I would be interested to see what others have to say. I should point out though that you have to first describe what the problem is. Resin printers are unrelated to FDM printers in their entire mode of operation and there are other systems e.g. SLS, SLM and EBM (not usually for domestic use) that use completely different materials to achieve the same result: a 3D part.

I’ve already gone to some lengths to explain my thoughts and what’s scientifically accepted on this and I’m not about to bore everyone else by repeating that ad nauseum. I’m a little confused as to why you feel it necessary to provide links to a bunch of links on science and skeptical thinking though. Have you not heard the old adage about “teaching granny how such suck eggs?”

Apropos to your claims in Post #37 where you linked not just “LiveScience” but also “Cleanwateraction” in relation to something you know very little about. Here’s a professional chemist with over 20 years in the field at one of those sites on both of these elements.

Perhaps you’d like to go over there and tell Mr Pearcey that he’s taken the wrong colored pill too?

Thank you for for using the links I shared, there is hope for critical thinking!

DrVax already has posted he does not like resin printers, I was hoping others had insights of the printing environment risks they wanted to share.

I was hoping you’d admit you’d been wrong about hexavalent chromium this whole time after admirably demonstrating you have absolutely no clue what you were talking about when you walked in this thread and stomped around like a pigeon in hob-nailed boots, clucking a famous quote from The Matrix.

If you want to be a skeptic young man (I’ll have to assume a gender here for the sake of simplicity) you need to own up when you’re wrong. And you were. Dead wrong. You relied on plagiarizing a chunk of text from Wikipedia and other badly-sourced material and then compounded that by lecturing us about science. Erin Brockovich is no environmental heronine - she struck gold simply because of a broken legal system and managed to exploit that in much the same way as the current litany of cases are being presented against Monstanto/Bayer in relation glyphosate.

One of the main skills of critical thinking is being able to evaluate evidence and, when that evidence shows your belief is wrong, you accept that and it’s usual to apologize, not to try and claim a victory that was never yours.

You owe this community that.

OK, you win, it will make you feel better.

I don’t think I defended Ms. Brokovich, ever, I perpetrated “copypasta”…

This isn’t about “winning” or “losing” it’s about humility and even now you’ve not demonstrated one iota of that; and I don’t appreciate your tone. My patience is wearing very thin.

You want to see what happens when I make a mistake (even a minor one)? Go back to page 2, post #28 regarding liquid mercury. I’d forgotten that while in liquid form, mercury is harmless and Ender5s corrected that:

The gaseous form or mercury is what used to cause millinery workers to go insane. To make beaver pelt hats, the mercury had to be heated quite hot, causing a lot of it to vaporize (liquid mercury will evaporate to some extent at room temperature). The milliners would breath in the fumes, which went straight to their brains. Thus, the term "mad as a hatter

You don’t see either of us putting up a pet lip and sulking. I accepted I was wrong and we moved on. I find it’s disarming to make light of a (non-critical) mistake because it demonstrates good will. You’ll see scientists get into heated debates and often raise voices or swear at each other, but once a consensus is established, we get behind that.

If you bothered to read my posts, you’ll note that I’m happy to admit where things are not my specialty and I’m perhaps speculating based on what I know. As a good rule of thumb, if a big flashy website makes a claim, particularly if it’s strident doom-gloom and Armageddon-like, you can probably take it with a pinch of NaCl. Natural News is one such odious collection, as are Mercola, Infowars, Prisonplanet, 911truth and even the Huffington Post and the Intercept! Real science websites are rarely flash and they are often text-heavy with numerous detailed citations and long discussions. I’m limiting mine here simply because I don’t want to belabor our host with complaints about me dominating a thread with stuff which is only tangentially related to 3D printing.

As for Ms. Brockovich…

Chromium-6 in Tap Water: Why the ‘Erin Brockovich’ Chemical Is Dangerous"

You are free to choose the red or the blue pill and believe what you choose to believe, opinions are not facts…

The emphasis is yours, although that could have come from lazy “copypasting”. Not to mention citing other dubious and basically badly informed sources before lecturing the rest of us about skepticism. You’re right that opinions are not facts, but right from the get-go, I was quite clear about the science surrounding this and my understanding of the science of PTFE pyrolisis. It was abundantly clear to me that you’d already taken up a position on Cr6 and selected the search results that supported your own preconceived ideas.

I was similarly unaware of the toxicology of Cr6 when the movie came out and I had to go look it up and talk to chemists before opening my mouth about it. It’s clear that there are still a lot of sites that maintain the idiotic suggestion that Brockovich was something other than in the right place at the right time and was lionized by a movie. If I was making a film about Brockovich (or similarly dishonest people) you can be damn sure that wouldn’t hold back on showing her for what she is. But selling a story like that in Hollywood is impossible - the same for Hedy Lamarr who, it’s widely and fallacious claimed invented FHSS.

People prefer convenient fantasies to hard truth, it’s human nature.

In a separate post, you said:

I would like to believe that the participants in the forum are of above average intellect, citizens of Lake Wobegon?

I’m struggling to understand how else that could be interpreted other than as a poke at myself or the others already in this discussion and the wider forum. That’s passive aggressive and it’s not smart to get in to a, shall we just say, competition with people who have already demonstrated a strong background in the topic.

“I would like to believe that the participants in the forum are of above average intellect, citizens of Lake Wobegon?” I don’t think our expectations pf you are that high.

https://www.atsdr.cdc.gov/csem/chromium/signs_and_symptoms.html

Over and out, discuss amongst yourselves