Just for those who delight in useless trivia: According to this article, siphons work by gravity, not air pressure differences. Therefore, siphon fed airbrushes are not really siphon fed. I wonder, what would the correct term be, and why are the airbrush companies lying to us? [:D]
Don
LOL!
Siphon is still the correct terminology to differentiate between a gravity and siphon feed airbrushes. Gravity feed requires nothing other than gravity to feed the paint to the needle, where siphon feed requires air pressure to start the siphon process.
Besides, Hydrostatic Pressure feed is too much of a mouthful!
Some people have far too much time on their hands. Probably a nerd physicist with nothing better to do. [:D]
Actually that makes since and siphon fed airbrushes actually aren’t even based on the flawed dictionary definition. A siphon moves from high to low, so it is obviously based on gravity. If you have ever tried to siphon fluid you know you have to put the hose exit below the fluid level or you will empty the container you are trying to fill.
Vacuum or venturi airbrush would probably be a more accurate term, since vacuum will raise a fluid. High pressure (atmosphere) will push a fluid towards an area of low pressure even if it is higher than the source. Of course a gravity fed air brush also benefits from the effect.
Hey I run fire pumps for a living so I have to be familiar with these concepts, however I never took the time to think about the physics of a siphon, I’ll look smarter the next time I each a pump ops class. [:)]
Not that I’m suggesting we change the well established use of siphon for a “siphon” fed airbrush.
As a retired nerd, I resemble that remark. [:)]
By the way, I think simpler and more accurate terminology would be: bottom fed, side fed, and top fed.
Now, who wants to write all the airbrush manufacturers and tell them to quit trying to fool us? [:D]
Don
Well, Badger uses both siphon and bottom, so they’re already on board!
I personally don’t like bottom feed. Bottom feeder sounds like a lawyer (no offense to any lawyers out there! Well, maybe a little!).
HEY! I’m a lawyer…but i use a gravity fed a/b - does that make me a better type of lawyer? [:P]
Chris.
LOL! [:D]
The English word “siphon” came from Greek that meant pipe or tube. I believe most of the siphon feed aribrush have a tube in it. So, the airbrush company might not have lied to us.
Siphon is used also in zoology for tubular organ, especially of aquatic invertebrates such as squids or clams, by which water is taken in or expelled. In verb, it means suck off by any means. For example, “to siphon off profits into a secret bank account”.
Siphon does not work in vacuum. The liquid was “pumped” by the atmosphere pressure difference created by gravity, but not gravity directly.
Ok, ok, I am splitting hair.
Well, whatever we end up calling it, since most of us prefer gravity fed, we should be able to agree that siphon fed airbrushes suck.
Sorry, couldn’t resist that!
A “siphon feed” airbrush works wonder in Don Wheeler’s hand. I can’t say it sucks.
Then how does it pick up the paint? [:D]
On second thought, the aribrush company does lie to us. All airbrushes “siphon” paint into the nozzle to “spray” out.
There is no such thing as a “gravity feed” airbrush. If so, we could have save the dollars for the compressor and buy more models instead. You can test it. If you have a “gravity feed” airbrush, turn off your compressor and see how much paint will come out. Not nearly enough under gravity-feed only.
All airbrushes “siphon” paint into the nozzle by the low pressure created by the air stream instead of a lower gravity point like the traditional siphon. Gravity either works against it in airbrush with bottle below the body or assist it with cup above the airbrush body.
(The noun “Siphon” is a tube or conduit bent into legs of unequal length, for use in drawing a liquid from one container into another on a lower level. The verb “siphon” can apply to drawing fluid using lower pressure created by a siphon or other means.)
If so, siphon should work in a vacuum. But it is NOT the case.
Alright, enough hair splitting. [*-)] This post is for nerds only.
Online, with it’s credit card!
I am in tendency to agree that siphon is incorrect, in the same manner that gravity fed is also incorrect. like suggested it should be top or bottom fed.
Neither the “Siphon” or “Gravity” brushes & guns operate in accordance with their names, both work using an aspirator / eductor jet pump & utilise the Venturi effect - ?
If correct, this means that we have the Italians to thank for all the wonderful Japanese, American, European & Chinese spray toys we use! It also means that the Gravity & Siphon products are really not that different, although I still will not be rushing out any time soon to get a bottom feeder.
Isn’t this merely a restatement of the old article about whether a vacuum (or reduced pressure) sucks or pushes?
They both work in the same way. They all suck! One just has a cap (jar bottom) on the reservoir to keep the paint in.
I think siphons suck (personal opinion).
I have noticed that there seems to be whole lot of argument all over the interweb in regards to weather a siphon can work in a vacuum or not. I understood that a siphon relied on hydrostatic pressure alone, but looks like it may rely on atmospheric pressure to start the process?
It’s pretty amazing that in this day & age that argument still goes on about something that on the surface looks so simple?
I suppose surface tension is another discussion altogether.
Ah, but doesn’t atmospheric pressure decrease as altitude increases? That would mean the air pressure on the tank would be less than the air pressure at the end of the hose. The difference would tend to push the water back up the hose. The area exposed to air is much greater in the tank, but pressure is measured in pounds per square inch (or other units) so that shouldn’t matter.
I’ve seen arguments both ways on whether a siphon works in a vacuum. I would vote yes, but I wonder if anyone has ever actually tried it. I love the picture. It looks like something by my hero, Rube Goldberg.
Boy, this is getting nerdy. [:)]
Don
That pic is a drawing by Slug Signorino, who illustrates for Cecil Adam’s syndicated column “The Straight Dope”.
Siphons do work in vacuums, but only under special circumstances:
Personally, I don’t think the “new” answer is 100% correct, either. I suspect that it’s a combination of air pressure, gravity, and the tensile strength of the material being siphoned. After all a siphon is limited to the same height restrictions a barometer is, and those rely completely on air pressure.
Gravity fed works as a term to describe that form of airbrush, as the paint medium is fed via gravity. The airbrush needs air pressure to create the venturi effect to atomize the paint, but paint will drip from the end of an opened airbrush through gravity alone.
Siphon is used to mean a liquid passing along a tube, and siphon fed airbrushes do that, so I’m sticking with the name. If one wants to get nit-picky “Venturi Siphon” would suffice as a term.
Boy, you are one smart nerd. I was just trying to split hair and out nerd you. The siphon action is driven by the pressure difference of a liquid height between the inlet and outlet of the siphon. In a sense, you are right the first place saying that siphon is gravity driven.
The picture is just for fun. It is NOT a real representation of siphon. Siphon does not work in vacuum because the liquid boiling point will be so much lower than room temperature, the liquid will evaporate before the siphon starts. It is a theory vs. reality question. I am an engineer and naturally drawn to the reality. If someone discovers a siphon working in vacuum video, it will be amazing to see.
It is better nerdy than nasty.