Wikipedia:Reference desk/Archives/Science/2014 November 16

= November 16 =

Width of gas lines.
I was running some gas lines for a unit heater i bought and the manual said i needed larger diameter pipe run depending on the distance the pipe was traveling.

I assume this is to keep a steady pressure, but the pipes throttle at the beginning and the end to a much smaller diameter, so i would think that the throttling would bottleneck the system no matter if i increased the pipe diameter AFTER the throttle.

but apparently it doesn't matter. Why exactly do i need larger diameter piping if i'm going a larger distance? how does an increase of diameter allow for an increase of flow rate? and why does it not matter if there is a reducer on either ends of the pipe?

70.210.70.252 (talk) 02:37, 16 November 2014 (UTC)


 * Same thing happens with electricity. Longer extension cords need to be heavier gauge wire for the same load. Pipes exhibit resistance to flow based on their diameter AND length. For short runs the differences can be miniscule, but natural gas pressure in household lines is measured in ounces, so even tiny differences can affect the flow rate. 50.126.104.156 (talk) 04:11, 16 November 2014 (UTC)


 * Just because it's restricted to being narrow at either end (pressure loss for those lengths), it would be even more restricted overall if it were narrow between them too. That is, there is resistance (and increasingly so, as the IP mentions) all along the way, not just a limit based on the narrowest point (as you seem to suggest by the idea of throttling/bottleneck). For lots of gory details, see . Not to say that a very narrow inlet couldn't have an overall limiting effect, but it's also the on-going effect between the ends too. DMacks (talk) 03:39, 18 November 2014 (UTC)


 * Lot's of reasons and electrical analogy is only one. Another concern is venturi effects.  Larger pipes reduce the pressure drop as the velocity is slower.  The danger is a high BTU appliance at the end of the run with taps along the way.  You don't want your gas furnace to draw air in from the stove burner due to velocity pressure drop.  It's important to calculate distance and BTU requirements and taps.  There are standard distance/diameter/BTU building code formulas that you can find (I don't have them handy but I've used them before). I believe throttling out of the meter is intentional to maintain a large pressure diff across the diaphragm (outlet is lower pressure during flow and it's not a limiting case).  --DHeyward (talk) 22:28, 18 November 2014 (UTC)

Rosetta Orbital Period
Since the comet has such low gravity, will Rosetta be able to maintain a conventional orbit around the comet? If so, how long will that orbital period be? I am guesstimating about a day (24 hours). Altitude 3 miles, orbital path 20+ miles, escape velocity 1 MPH. 50.126.104.156 (talk) 04:05, 16 November 2014 (UTC)


 * I believe that Rosetta isn't in a 'free' orbit. It does several powered 'turns' in each orbit (I think, every 60 degrees).  So, in effect, it's flying a bunch of nearly straight lines at much higher than escape velocity.  I read someplace that Rosetta's speed relative to the comet is about 25 meters/second (sorry, I don't remember where I saw that).  According to our article, the orbital distance is 29km (roughly) - although at times, they've reduced that to as little as 10km and started out at 100km.  If the orbit was circular, then the circumference of that orbit is 2 pi x 29000 meters, which is around 200,000 meters.  At 25 m/sec we get an orbital period of around 7000 seconds...around 2 hours.  For a more exact answer, we'd need more details about the shape of the orbit and the fuel burns to keep it like that.  When it was out further from the comet, I believe the 'natural' orbit was 26 days.
 * An orbit that long would be useless while interacting with the lander because there would be periods of many days when they'd be unable to communicate. Hence the powered turns. SteveBaker (talk) 15:45, 16 November 2014 (UTC)

Signals from UFOs
If there as many UFOs out there as people would have us believe, why dont we pick up some electromagnetic signals from them via, for instance, the SETI program? Also, if UFOs exist, what do they want?--86.182.54.46 (talk) 13:13, 16 November 2014 (UTC)


 * We don't hear little green men talking on their walkie-talkies because they are not here. There is almost certainly life out there somewhere (it being a big galaxy and an even bigger universe), but there is no reliable evidence that we are being visited.  Alien UFOs, the Bermuda Triangle, the Loch Ness Monster, and ghosts are all more cultural phenomenon than they are scientific ones. Do you want to believe? -- ToE 14:29, 16 November 2014 (UTC)


 * There are a few scientists who have theorized that there may not be any complex life anywhere else in the Milky Way, based on extremely low values in the Drake equation. I am aware of one that said that the merger of the mitochondrion with the prokaryote was an extremely unlikely event.  Other, more commonly theorized values for the factors in the Drake equation compute the likelihood that there is life elsewhere in the Milky Way, but not within communicating distance.  Remember that the Milky Way is an astronomically large place.  If relativity is correct and the speed of light is invariant, then there are limits to how far intelligent beings, even long-lived ones, would travel.  Even if superluminal travel is possible, the Milky Way is still an astronomically large place.  Robert McClenon (talk) 21:25, 17 November 2014 (UTC)


 * As to whether UFOs are a cultural phenomenon, Carl Sagan has theorized that there is something about humans, maybe even in brain wiring, so that humans want there to be other beings with whom we can communicate. In the past, this desire resulted in various sorts of folkloric humanoids such as, in European culture, dwarves, trolls, and elves, having other names in other cultures.  In modern times, they are extraterrestrials.  So maybe they are both a cultural phenomenon and a psychological phenomenon.  Robert McClenon (talk) 21:30, 17 November 2014 (UTC)
 * If by "UOFs" you were not referring to aliens sighted visiting Earth but instead you were speaking metaphorically of extraterrestrial intelligence in general, and your question was why SETI has not been successful to date, then you should make that clear. -- ToE 14:42, 16 November 2014 (UTC)


 * Upper atmosphere objects. Do YOU believe these? []--86.182.54.46 (talk) 14:47, 16 November 2014 (UTC)


 * There is a large community of people out there who take NASA imagery and "enhance" it. Sadly, because they are unschooled in how to do image enhancement correctly, they make stupid mistakes and generate 'artifacts' that look just like UFOs or alien cities or whatever their fevered imaginations can come up with.  My favorite way to demonstrate that is this from a post I did here back in 2009 were I take the period at the end of the original question and 'enhance' it until there is a really clear picture of an alien city, complete with buildings, streets and shadows that are convincingly cast by those buildings!  I use it so much, I made a copy on my own website:


 * http://sjbaker.org/wiki/index.php?title=Alien_City_hidden_in_Wikipedia_post


 * I've seen photos of UFO's that were the result of this exact same thing. A tiny white speck in an image (could be dust on a lens, or a star or something) get "enhanced" until you get a nice blurry image that looks just like a classic UFO.
 * SteveBaker (talk) 15:17, 16 November 2014 (UTC)


 * Aliens are bound by the same laws of physics that we are. Getting from wherever they live to us would take hundreds to thousands of years - and they'd have been unlikely to detect our civilization hundreds or thousands of years ago.  It's unlikely that they'd even be able to detect that we're here.  With our present technology, we'd be unable to detect a human-scale civilization orbiting a star more than a couple of lightyears away.  So:
 * "If there as many UFOs out there as people would have us believe"...well that number would be zero...assuming you're listening to people who have seriously thought about it!
 * "if UFOs exist, what do they want?"...they don't exist, so the question is moot.
 * If you really want an answer to the hypothetical question of what it would be like if they DID exist, then I suppose the chain of reasoning is something like:


 * If they could get here at all, they'd have to have some pretty amazing technology.
 * If they wanted to destroy us, and they are that advanced, they could easily do before we ever knew they were there. If they were prepared to spend hundreds of years patiently getting here, they could spend 50 more years to gently deflect a dinosaur-extinction-event sized asteroid to wipe us all out...and we'd never even know they'd done it until we were all dead.  So, clearly that's not what they want.
 * If they wanted us to detect them, they could very easily make themselves known by any number of impressive and undeniable ways - and they clearly haven't done that either.
 * So they must want to remain hidden and so they certainly wouldn't go around broadcasting radio signals that they know we can detect.
 * Ergo, if they exist at all, we're unlikely to be able to detect them.


 * If there were UFO's in orbit around the earth, they might communicate with each other using lasers or some other sort of directed signal that avoided splattering light or radio in all directions. They'd undoubtedly use stealth technology that would prevent us from picking them up with radar or other such tricks.
 * SETI goes to a lot of trouble to eliminate signals that are too close to earth to be a signal from another star system - so even if they could pick up UFO's, they'd be actively ignoring them...but there are lots of other people out there who track space debris and look for unusual satellite activity from potential (human) enemies who could detect an easily-detected alien ship.


 * What do they (hypothetically) want? Who knows?  We can't detect them.


 * A species that's capable of all of this wouldn't be dumb enough to show themselves to people by abducting them, doing experiments on them and letting them go afterwards...if they were trying to keep themselves hidden, they're doing a really terrible job of doing that.


 * All of these sad people with nothing better to do in their lives than make up stories are feeding you bullshit...and until a UFO lands on the Whitehouse lawn...we can probably ignore these reports. People are endlessly capable of deluding themselves and going out and making up a pack of lies to make themselves feel more important...it's a part of human nature.


 * SteveBaker (talk) 15:02, 16 November 2014 (UTC)
 * And Steve has only shown one of many types of image distortion only caused by a specific conversion artifact of the JPEG image compression algorithm. There are many, many other image artifacts that can be caused by camera optics, digital sensors, and all kinds of other complicated software processing, all of which are omnipresent on today's digital cameras!  If one is looking for noise, noise is easy to find!   Nimur (talk) 16:12, 16 November 2014 (UTC)


 * Yes, exactly. In my example, in addition to the JPEG compression artifacts, I also had our hypothetical UFO investigator use an "Edge enhance" function - which is great at highlighting edges at normal pixel sizes - but when you enlarge the image, you get dark and light fringes along all the edges - which make just dandy fake shadows.  I've seen dozens of supposed alien vehicles and buildings that had inadvertently been created from nothing more than edge enhancement and subsequent magnification. SteveBaker (talk) 23:32, 16 November 2014 (UTC)


 * As far as why an alien species might come to Earth and yet remain hidden, the obvious answer is for scientific study of Earth life, while following a version of the noninterference directive. Earth scientists would absolutely love to find any extraterrestrial life to study, even if it was only as complex as a virus or bacterium.  StuRat (talk) 15:16, 16 November 2014 (UTC)


 * This is a common idea - but if there is an 'noninterference directive', why are they (supposedly) kidnapping dozens to hundreds of humans, doing nasty experiments on them and then releasing them again? If a species that was that advanced wanted to investigate us without being noticed...I really don't think we'd notice them. SteveBaker (talk) 23:32, 16 November 2014 (UTC)


 * Well, either the infamous "anal probe" part is entirely made up, or perhaps their noninterference directive only applies on a mass scale. That is, they don't want to interfere with the human species, but individuals don't much matter to them.  We have similar attitudes towards many Earth species, where we want to protect them, on the whole, but still don't mind killing or experimenting on a few individuals. StuRat (talk) 19:00, 18 November 2014 (UTC)

A few scientists have actually addressed this question, but their scientific inquiries are usually drowned out by the sea of nonsense, fiction, and pseudoscience. As a start, you might look for Intelligent Life in the Universe at your local library. It was written by Iosif Shklovsky and adapted into English by Carl Sagan. The book provides insightful perspectives on intelligent extraterrestrial life from some very intelligent terrestrials. Nimur (talk) 16:21, 16 November 2014 (UTC)


 * What has not been pointed out is why there are so many UFO's up there. A UFO is simply any aerial object or phenomena that the observer can not recognise as (say) a Boeing 747, hot air balloon, atmospheric sounder, classified military drone etc. Hence the official term unidentified flying object or UFO for short. Just because a DEFCON alert is issued, does not mean that these (possible) alien objects are of extra terrestrial origin. They might be Russian reconnaissance aircraft or a publicity inflatable that has escaped it tether.  Most civilian observers of UFO's don't have  radar or any other apparatus with which to objectively record what they witness. If they did, they my well receive electromagnetic signals.  Also, people are easy fooled. I saw a youtube video shot at  night of which was claimed as an 'obviously' extra terrestrial craft because it was doing maneuvers that no known terrestrial craft could do – except I have seen   Airship Industries craft maneuvering the exactly same way. Airships can remain stationary, tilt their noses up and down and suddenly change their apparent  shape by turning nose or tail toward the observer. They (Airship Industries) demonstrated their craft to the US defense industry as a possible radar platform – in the very same desert -where the video was shot.  It obviously  had its  internal gas bag lights on – hence it appearance in the sky. This was maybe in order  that ground observers could see the maneuvers. These internal lights are there, so that they can serve both  day and night as  advertising bill boards.  But to the audience at this UFO convention, it was by definition a true UFO as no-one identified it for them. If the object escapes the observers experience, it is by definition a UFO and thus there are a lot of them about (both UFO's and observers).--Aspro (talk) 18:24, 16 November 2014 (UTC)


 * Indeed. As my father-in-law (ex-RAF) used to say, "Any FO is a UFO until it is I". (Any Flying Object is an Unidentified Flying Object until it is Identified) --TammyMoet (talk) 20:39, 16 November 2014 (UTC)


 * That reminds me of the RAF identification friend or foe system. It worked well at night too, so everybody was told that fighter pilots ate carrots to help them see in the darks, to hide the real reason from the Luftwaffe high command (namely the gravitationally challenged Hermann Göring) for so many successful RAF night-time intercepts. To be pedantic, should mention also, that they donned  red goggles  whilst on the ground to preserve their night vision and they were very well trained. --Aspro (talk) 21:37, 16 November 2014 (UTC)


 * There is somewhat of a disconnect between the strict dictionary definition of UFO vs. the way it's used in popular culture. These supposed extraterrestrial vehicles were initially being described as "flying saucers". Donald Keyhoe's organization NICAP called them "aerial phenomena". The term UFO was eventually latched onto, and over time its pop culture meaning usurped its natural meaning. ←Baseball Bugs What's up, Doc? carrots→ 13:55, 17 November 2014 (UTC)


 * I really doubt that there are many people left in the world who use "UFO" to mean anything other than alien spacecraft...just like nobody uses "gay" to mean "happy" or "computer" to mean a person who does arithmetic for a living. The word has changed meanings and we're all just waiting for the dictionaries to catch up and mark the old meaning "(archaic)".   I'd bet that when someone officially reports an unknown object in the sky these days, the official parties involved steer well clear of calling it a "UFO"...just because every time they do it and the nut-jobs get to hear about it, it's a whole major nonsense-fest.  So there are almost certainly new terms used to replace the original sense of "UFO" - maybe "non-specific aerial contact" or something.  However, this doesn't prevent people from telling us that the term has some dusty old archaic meaning.  Well, I got news for you - it doesn't.  Here in 2014, "UFO" means "Aliens spaceship" and any other interpretation is mere pedantry. SteveBaker (talk) 21:28, 17 November 2014 (UTC)


 * Steve, since this is a reference desk, this is not the place for your scorn and ridicule of people no matter how correct or not you may happen to be in your assessment. Furthermore, you will need a citation for the formal meaning being archaic, since the Wiktionary entries include both meanings: https://en.wiktionary.org/wiki/flying_saucer https://en.wiktionary.org/wiki/UFO and https://en.wiktionary.org/wiki/unidentified_flying_object#English -Modocc (talk) 00:20, 19 November 2014 (UTC)

I also take issue with the
 * I can't believe that no-one has mentioned it earlier, but the Fermi paradox of relevance here. CS Miller (talk) 13:39, 17 November 2014 (UTC)


 * All the above is all very well, but how do you explain the strange objects moving at high speeds as shown ON NASAs OWN SHUTTLE CAMERA? as linked to in my second post??86.180.139.169 (talk) 18:12, 18 November 2014 (UTC)


 * The article UFO sightings in outer space has some references listed that may be helpful to you. --Modocc (talk) 00:54, 19 November 2014 (UTC)

Plant respiration
Where can I find information about plant respiration? I'm looking for specific numbers which give plant respiratory rates during non-photosynthesis periods (aka night) for a variety of crops. A web search gives me several "online answers" type sites which suggest that plants give off CO2 at night at about 10% of the rate that they take it in during the day, but I've not been able to find anything more specific or anything at all authoritative. Our Respiration is a disambiguation page and Respiratory system doesn't have much useful to say. Do we have more on the subject? -- ToE 14:18, 16 November 2014 (UTC)
 * Go to Google Scholar and do a search on "dark respiration." There's plenty of info out there. Short Brigade Harvester Boris (talk) 16:14, 16 November 2014 (UTC)
 * In addition, check out the equations and references used by WIMOVAC, which is a mathematical model for plant physiological processes. The dark respiration model is explained here: . Mihaister (talk) 08:04, 17 November 2014 (UTC)
 * Thank you very much, both of you. "Dark respiration" was certainly the term I need to be searching on.  I haven't found a general table yet, but a few formulae suggest values greater than 10%.  For instance, McCree 1974's abstract states that clover and sorghum have a nightly efflux equal to 14% of the previous daytimes influx, plus and additional maintenance component of the efflux which is proportional to the dry weight of the plant, 1.43% of that weight for clover and 0.54% for sorghum (more details behind a paywall).  And I appreciate being pointed to WIMOVAC, as it is mathematical modeling I am interested in. -- ToE 12:44, 17 November 2014 (UTC)
 * Check out Ameriflux and FluxNet. You'll generally want empirical data more recent than 1974, as the eddy covariance tower technology has really changed how accurate measurements of dark respiration can be. Although it's not the primary mission, a lot of research on biofuels and greenhouse gas emissions associated with agricultural production will mention dark respiration numbers. So I'd also try searching google scholar for things like /dark respiration [crop] eddy covariance/ SemanticMantis (talk) 15:43, 17 November 2014 (UTC)
 * Here's a nice paper that covers dark respiration in few different crops . I actually know a small bit about the mathematical modeling of plant physiology (my research expertise is in applied math/theoretical ecology, and this stuff is tangentially related), so fee free to drop me a line at my talk page if you'd like to discuss further. SemanticMantis (talk) 17:46, 17 November 2014 (UTC)
 * Thanks SemanticMantis! -- ToE 18:26, 19 November 2014 (UTC)

Water on building demolition


What's the point of spraying water on a building demolition? Keeping down dust? Or should I simply assume that they had feared fire? Image context — it hadn't rained in a few days (this was last Tuesday, and there was a moderate rainstorm on the previous Saturday), with unusually high temperatures in the 60°s F, while "surrounding" days were in the 40°s and 30°s F. Although the demolition machine is pausing at the moment of the picture, the pause is momentary; its noise could be heard throughout the downtown for most of the afternoon. Water spraying continued, with both demolition machine and water hitting the building at the same time. Nyttend (talk) 15:11, 16 November 2014 (UTC)


 * Keeping dust down. Fire is unlikely to be caused by demolition, assuming they disconnected any natural gas lines first. StuRat (talk) 15:21, 16 November 2014 (UTC)


 * For that matter, dust itself can be a major hazard if it happens to be flammable. Considering what the dust from a building demolition is likely to consist of, you wouldn't expect it to be flammable, but hey, who knows what those people had stored in there? --65.94.50.4 (talk) 09:05, 17 November 2014 (UTC)


 * We even have an article: dust abatement. Some cities or counties require spraying water on certain types of construction sites.  As I recall, in North Carolina, where water was plentiful, they would even spray down the ground around the construction site.  Nimur (talk) 15:54, 16 November 2014 (UTC)


 * Many old houses have asbestos, mold and other toxic material, you don't want that dust to fly to the neighborhood Joc (talk) 17:50, 16 November 2014 (UTC)
 * My city requires it as well (Ramat Gan - Israel). The reason is as mention above: to keep dust down and to prevent the dust of the environment.213.57.28.207 (talk) 18:01, 16 November 2014 (UTC)
 * I doubt that if the building has asbestos, just springling water will be enough. Demolishing and decontaminating asbestos contructions is more difficult than that.Senteni (talk) 18:53, 16 November 2014 (UTC)
 * See Google Street View of the building; it's a modernist structure probably newer than US federal laws restricting asbestos usage. Nyttend (talk) 03:31, 17 November 2014 (UTC)

what is the difference between potentiation and synergism? (pharmacology)
213.57.28.207 (talk) 17:57, 16 November 2014 (UTC)


 * Is this a homework question?
 * Let's take a practical example. To make vaccines more potent aluminium compounds are often added. These compounds on their own have no anti-viral effect. Clavulanic acid in antibiotic is another example. Synergism is were 'both' substances  have an effect. For example: Alcohol and barbiturates  are both  depressants,  Taken together, the  depressant effect is greater because they work together. Incidentally, If one gets a pain around where the liver is, up to two weeks after finishing taking a  clavulanic acid enhanced antibiotics, see your doctor to have a yellow card submitted.  In the US it would be these people:  This bad reactions appears to be  under reported. These enhanced antibiotics should not be used as a first line  treatments IMHO. I'm not giving medical advice but directing readers to a professional. .--Aspro (talk) 18:52, 16 November 2014 (UTC)

Proper adhesive
I have decided to make myself a custom tea infuser but I am struggling to find a proper adhesive for that purpose. Is there any glue for plastic that can have a direct contact with food and withstand up to 100 °C? Will cyanoacrylate do? It works for plastic. Water does not do much to it either. It must be non toxic as is used in medicine. But I failed to find info on how toxic it actually is other than its fumes may be dangerous. Another doubt is about the temperature it can withstand as I don't have much data no that. 128.69.7.196 (talk) 21:46, 16 November 2014 (UTC)


 * Groan....Epoxied resins are probably better as they are also stronger and the right ones are biologically inert. See: Personally, I would just use  a proper  Teapot and use real, genuine, lose leaf tea. See:ISO 3103 . Read and do! Lastly, enjoy your first cup of real tea. If you like milk, put it in the cup 'first'. No augments! Milk first.--Aspro (talk) 22:40, 16 November 2014 (UTC)


 * How about just buying a tea ball ? StuRat (talk) 22:46, 16 November 2014 (UTC)


 * Sacrilege! The leaves need to circulate. A tea strainer employed during the pouring out, shows one guests that you now how to brew a really good steaming hot cup of tea. Otherwise, you might just as well serve them up with something from a vending machine which fills the cup up with a liquid that is  almost, but not quite, entirely unlike tea.--Aspro (talk) 23:18, 16 November 2014 (UTC)


 * I have given up asking for a cup of tea in the US because all I get is a cup of lukewarm water and a pouch dangling on the end of a string and a little plastic thing that is supposed to contain cow juice but no cup of tea in sight and then they have the nerve to bill me for over a dollar for something that is only good as an insecticide. How is it, that a nation can put a man on the moon but can't achieve the simple art of brewing tea?--Aspro (talk) 23:35, 16 November 2014 (UTC)


 * Some might argue that the time saved over not obsessing over the precise formulation of warm water with tiny shrivelled up leaves in it is precisely what enabled them to reach the moon. The British effort to get to the moon foundered on the heated debate of when to add the milk in a micro-gravity environment.  But then, I'm a Brit who can't stand even the smell of tea...YUCK! SteveBaker (talk) 04:55, 17 November 2014 (UTC)


 * Astronauts made their way to the moon as the result of the efforts of a small group of people. Saying it was the nation that sent them to the moon is an example of metonomy. Similarly, the nation has never made, or attempted to make, a cup of tea. Cups of tea are made by individuals, not nations. Dolphin  ( t ) 05:31, 17 November 2014 (UTC)


 * I disagree. Sending the first man to the Moon required that massive tax dollars be spent on the project, which required a large, wealthy population, with the political will to spend that money in that way (or a dictator who gave them no choice). StuRat (talk) 19:49, 17 November 2014 (UTC)
 * Um...&lt;small&gt; comments are intended to be jokes - no need to take them so seriously. Of course a small group of people were responsible for all of the bravery, the clever science and engineering it took to get to the moon - and a very large number of people had to have the collective will to vote for politicians that wouldn't cancel the entire thing...but remember the &lt;small&gt; font ! SteveBaker (talk) 20:39, 17 November 2014 (UTC)


 * Which plastic? Different plastics need different glues, but in general it's impossible to glue plastic. Cyanoacrylate won't glue plastic very well, truthfully nothing will.
 * Usually you can use acetone to dissolve the plastic, put the pieces together and wait for the acetone to evaporate, and then they are one piece. (That's how commercial PVC glues work.) Acetone is pretty non-toxic and evaporates really well, so that would be safe for food use. Ariel. (talk) 06:22, 17 November 2014 (UTC)
 * I own and operate a small business providing a set of very specialized repair services to the construction and home improvement industry in the United States. It is impossible to generalize about "plastics" in a question like this. The performance of adhesives on polyethylenes is completely different from the performance of the same adhesives on polystyrenes. I work most commonly with mineral filled sheet acrylic products, and sometimes with polyester/acrylic blends. In the past, I worked with plastic laminates, where rubber based "contact adhesives" are used routinely, but where urethane adhesives are used in higher-end custom work. In my day to day work, when high performance and a highly inconspicuous seam is critical, we use catalyzed acrylic adhesives most commonly, which we purchase in a wide range of color tints to match the background color of the sheet product. For rapid but more visible bonds, we often use cyanoacrylates. Silicone provides a very strong, flexible bond, but that is not truly inconspicuous. We use hot melt adhesives for temporary tacking and "clamping" but they shouldn't be considered permanent in exposed situations, as exposure to alcohol (such as vodka) will cause the glue line to fail. Construction adhesives (called "panel adhesives" in the U.S.) are strong, inexpensive but ugly. In our line of work, we rarely use epoxies these days, and their performance characteristics vary. Also worthy of mention are UV cured "dental grade" adhesives, which can be tinted and filled with particulates to simulate the substrate, leading to very inconspicuous bonds. Selection of the best adhesive is always a trade-off of factors including compatibility with the material being bonded, strength, appearance, cost, cure time, flexibility, toxicity, availability and things I have forgotten this late at night. There are no easy answers in this area. By the way, acetone is not non-toxic. Sorry. Cullen328  Let's discuss it  07:15, 17 November 2014 (UTC)
 * Actually Acetone is pretty much non-toxic. People are always surprised when they hear this, but go and look it up and you'll see. The reason it's mostly non-toxic is that the body naturally contains some, and is able to metabolize it rapidly. (It's not completely non-toxic, don't go drinking it, but as solvents go it's very safe. It's certainly safe to use as a glue and then let it dry.) Ariel. (talk) 19:09, 17 November 2014 (UTC)
 * I'm not nearly as well-versed about plastics as User:Cullen sounds, but I strongly endorse several of his points: "plastic" refers to many hundreds of different types of material. Even if we consider only those plastics that are readily available to consumers, there are many categories.  If we use resin identification codes as a guideline, we can loosely group consumer-grade plastic into six general "types" plus a catch-all "other" category.  These categories are completely different kinds of chemicals!
 * Just for fun, I checked the FDA's web-page for food-safe adhesives. They linked to 21 C.F.R. Part 175, Indirect Food Additives: Adhesives and components of coatings.  In the United States, food-grade adhesives must come from that list of pre-approved chemicals; but there is the wonderful catch-all phrase that you will find in almost all FDA regulatory writing, permitting all "substances generally recognized as safe for use in food."  In concept, if you used one of these chemicals, your product would be compliant with food safety regulations - which is, needless to say, conceptually distinct from a product that is actually safe.  Cyanoacrylate is not on the listing in 21 CFR 175 §105 c(5) and I doubt it meets GRAS requirements.  I would wager that cyanoacrylate is neither compliant nor safe for use in food products.  Henkel North America publishes a Material Safety Data Sheet for Loctite Cyanoacrylate glue (the kind of CYA glue you'd buy in a hobby model-store).  Among the statements in the MSDS: "Not expected to be harmful by ingestion"; "The product will polymerize rapidly and bond to the mouth making it almost impossible to swallow. Saliva will separate any solidified product in several hours. Prevent the patient from swallowing any separated mass;" "Surgery is not necessary to separate accidentally bonded tissues. Experience has shown that bonded tissues are best treated by passive, non-surgical first aid."  So, if you follow the advice of this vendor, ... it should be harmless!
 * If I were building a home-made apparatus for brewing hot beverages for my own consumption, I would be very careful about the materials and glues I used. I would avoid cyanoacrylate entirely.
 * Nimur (talk) 18:17, 17 November 2014 (UTC)
 * Cyanoacrylates are routinely used in medical applications, such as an alternative to sutures for closing wounds. Cullen328  Let's discuss it  03:43, 18 November 2014 (UTC)
 * ... and in temporary repairs of dentures, but it is slowly dissolved by water (and tea).   D b f i r s   08:17, 18 November 2014 (UTC)
 * Cyanoacrylate glues are not only used for skin suturing - that's actually what they were first designed to be used for!  It's therefore unsurprising that you can easily get your fingers stuck together while using the stuff! SteveBaker (talk) 17:03, 18 November 2014 (UTC)