Hypo heavier than water?

[Cor]

In a recent discussion on washing wet plate collodion plates after fixing with hypo the phrase "hypo is heavier than water" popped up again. (The advice being that collodion plates after fixing should be washed standing up, in say a bucket so that the hypo could "fall" to the bottom since it is heavier).

I always thought that that was an urban myth brought to life by Fred Picker. But I cannot seem to find back the reasoning. And I can be wrong off course.

For myself; (assuming rapid fix and thiosulphate the same in this context), I never shake my bottle of stock or diluted fix before using it, but if hypo would be heavier, one should, shouldn't one?

Or there is a fundamental difference in washing out hypo from a collodion plate versus a "normal" film or photo paper, but I somehow doubt that..

So Myth Busters: Is Hypo Heavier Than Water, and should we wash out B&W photo paper upside down (emulsion side facing the bottom) in a horizontal tray?

Best,

Cor

 

[Ian Grant]

Weigh a bottle of new Fixer, then weigh the same bottle full of water, there's quite a difference - over 300g for a litre bottle. So yes Hypo solution is heavier than water.

And yes we all know that some solutions separate over time But the reasoning here is wrong, separation happens in solutions that have ingredients in suspension, not dissolved.

However the reason for not washing flat is bits of emulsion, dust etc can drop down onto the plate surface & stick there, the hypo comes out by diffusion not gravity

You can try putting a totally soluble dye into water, it'll be heavier and initially may drop but if you leave it the solution will become uniform, in the case of hypo we agitate to help this diffusion happen

Ian

 

[Marco B]

To illustrate Ian's point:

When you mix orange syrup to make lemonade for your children, you don't expect to see the orange color end up at the bottom of the glasses after an hour or so, do you?

Only supensions or mixtures of water with hydrophobic liquids like oils, may separate in time.

 

[Robert Hall]

11 lbs per gallon of Hypo, vs 8 lbs per gallon of water. A recently purchased 55 gallon drum of fixer weighed 600 lbs. (my poor truck!)

 

[Mainecoonmaniac]

Yes fixer is heavier than water. I assisted a Brooks graduate and long time friend and he made this film washer that's just an old milk jug with holes on the bottom and a 1/2" tab cut on top of it. You would wash the film under running water. The heavier hypo get's drawn to the bottom into the holes. I've had this washer for over 20 years and it still works great. Low tech, cheap price. Way cheaper then Fred Picker's film washer and I'm sure it works just as well.

 

[dpurdy]

11 lbs per gallon of Hypo, vs 8 lbs per gallon of water. A recently purchased 55 gallon drum of fixer weighed 600 lbs. (my poor truck!)

I would be curious to know what sort of place sold you a 55 gallon drum. It has become increasingly difficult to get the 5 gallon cube of Kodak Rapid Fix part A locally. I've been resorting to the 5 liter bottle and it is very expensive like that. I am looking into mixing my own.

 

[Vaughn]

Yes fixer is heavier than water...

But fixer in water all weighs the same.

 

[Kirk Keyes]

Yes fixer is heavier than water. I assisted a Brooks graduate and long time friend and he made this film washer that's just an old milk jug with holes on the bottom and a 1/2" tab cut on top of it. You would wash the film under running water. The heavier hypo get's drawn to the bottom into the holes. I've had this washer for over 20 years and it still works great. Low tech, cheap price. Way cheaper then Fred Picker's film washer and I'm sure it works just as well.

Despite Fred Picker's faulty logic in his film washer design, as Ian points out there are other factors that really come into play in washing films so it's not at all surprising that your friends' print washer works. (I'm surprised someone that attended Brooks had not been set straight on this bit of folklore. Maybe if he had gone to RIT...)

A solution of concentrated hypo does indeed have a specific gravity that's higher than pure water. But after the bulk of the hypo rinses off the surface of the film, it's diffusion that does the washing and movement of the water that speed the washing up. After all - even in an absolutely still container of water (high is truely impossible to create), Brownian Motion will evenly distribute (i.e. dissolve) the hypo molecules into the entire volume of water given enough time.

Since all print washers, regardless of whether the drian holes are on the bottom or the top of the washer, use running water, the movement of the molecules from Brownian Motion is greatly augmented by the flow of the water which distributes the hypo much faster into the wash water. The specific gravity of the hypo containing water is going to be so close to the specific gravity of the wash water, that there is no issue from the difference in densities. The force of motion from the movement of the water greatly exceed the force of gravity.

If I had to wait for the hypo that's in solution to sink to the bottom of my film washer, I would literally be waiting for eternity as it will never happen.

"Hypo heavier then water" is just one of those old photographic equipment manufacturer tales that just will not die...

 

[Ian Grant]

Yes but Kirk you'd only have to wait over-night to see the orange juice (squash) separate - sorry Marco. (When you buy an orange juice here they Juice 3 fresh oranges).

I'd never heard the "Hypo is heavier than water" thing until this thread

Ian

 

[RalphLambrecht]

Yes but Kirk you'd only have to wait over-night to see the orange juice separate (sorry Marco).

i'd never herad the "Hypo is heavier than water" thing until this thread

Ian

Oh yes, it's one of the oldest myths! It even lead to a company name for print washers (Gravity Works). Like all these myths, it's here to stay.

By the way, I just checked, 1 kg of hypo weighs exactly the same as 1 kg of water.

Sorry, couldn't resist.

 

[Vaughn]

Yeah, Ralph, but which would you rather have fall on you from a great height...a ton of loose gravel or a ton of loose feathers?

 

[Ian Grant]

Oh yes, it's one of the oldest myths! It even lead to a company name for print washers (Gravity Works). Like all these myths, it's here to stay.

By the way, I just checked, 1 kg of hypo weighs exactly the same as 1 kg of water.

Sorry, couldn't resist.

But 1 litre of Fixer doesn't weigh the same as 1 litre of water .

Ian

 

[ic-racer]

I believe that tall tales, urban legends, religions, and the like, get started with some subjective observation. In this case its not hard for me to see how this one got started. If you mix some dye with some fixer and drop it in a glass of still water it goes right to the bottom like dropping a rock in there.

 

[Marco B]

By the way, I just checked, 1 kg of hypo weighs exactly the same as 1 kg of water.

Sorry, couldn't resist.

That is only true if you measure them at exactly the same location. Gravity varies across the globe, and so does weight (but not mass) :

http://en.wikipedia.org/wiki/Mass_versus_weight

Marco

 

[ic-racer]

That is only true if you measure them at exactly the same location. Gravity varies across the globe, and so does weight (but not mass) :

http://en.wikipedia.org/wiki/Mass_versus_weight

Marco

Actually variations in gravity affect only the weight, not the mass as he has indicated in kilograms. (The weight would be in pounds or newtons).

 

[nworth]

Fixer is certainly heavier than water, but in the wash it simply diffuses into to water to make a uniform, but more dilute, solution. You throw away the wash water, usually on a continuous basis, so the solution becomes progressively more dilute until the concentration of hypo and its reaction products in the water is negligible.

 

[Mainecoonmaniac]

Thanks for busting the myth. So I'm wondering with the milk carton film washer, is it just the change of water that's washing out the hypo?

 

[Vaughn]

Yes, just the change in water -- with a little water flow to disperse the hypo leaving the paper (otherwise, locally the hypo concentration might build up too high right next to the paper for good diffusion of the hypo out of the paper) and no "dead" spots -- where there is no water circulation.

 

[CBG]

Thanks for busting the myth. So I'm wondering with the milk carton film washer, is it just the change of water that's washing out the hypo?

Just keep fresh water moving past the emulsion surface. The up or down or sideways direction of motion is inconsequential. Having a simple, workable design for your washer is most important. The rest is just details.

Currently I do not have a dedicated film washer. I just fill and dump right now. I do no less than ten total changes of fresh water, plenty of agitation, and no less than ten minutes washing for film. I would like not to be quite so handcuffed to the film washing process. I will soon get a film washer.

 

[RalphLambrecht]

Thanks for busting the myth. So I'm wondering with the milk carton film washer, is it just the change of water that's washing out the hypo?

Diffusion washing needs time for the diffusion to take place and water changes allowing it to take place. Slow running water prevents and equilibrium to be reached, keeping diffusion at the highest possible level.

 

[Martin Aislabie]

Actually variations in gravity affect only the weight, not the mass as he has indicated in kilograms. (The weight would be in pounds or newtons).

A Pound is a meassure of mass.

A Pound Force (which we often shorten to a Pound) if the weight of 1 Pound (lb) under the nominal gravitational force of the Earth.

I knew gravity varied with Latitude (its why Space Craft are launched from as near the Equator as possible - gravity is at a minimum there) but only recently found out that it varried with geographic position too - which is down to variation in thickness of the Earths Crust.

Martin

 

[Kirk Keyes]

I knew gravity varied with Latitude (its why Space Craft are launched from as near the Equator as possible - gravity is at a minimum there)

Actually, the reason for launching spacecraft from as close to the equator as possible is that there is greater rotational velocity at the equator than elsewhere. The poles have zero rotational velocity.

From http://en.wikipedia.org/wiki/Escape_velocity

"The escape velocity relative to the surface of a rotating body depends on direction in which the escaping body travels. For example, as the Earth's rotational velocity is 465 m/s at the equator, a rocket launched tangentially from the Earth's equator to the east requires an initial velocity of about 10.735 km/s relative to Earth to escape whereas a rocket launched tangentially from the Earth's equator to the west requires an initial velocity of about 11.665 km/s relative to Earth. The surface velocity decreases with the cosine of the geographic latitude, so space launch facilities are often located as close to the equator as feasible, e.g. the American Cape Canaveral (latitude 28°28' N) and the French Guiana Space Centre (latitude 5°14' N)."

 

[RalphLambrecht]

I was trying to get this thread back to photography.

 

[dancqu]

Ice Melt

I knew gravity varied with Latitude (its why Space Craft are
launched from as near the Equator as possible - gravity is at
a minimum there) but only recently found out that it varried
with geographic position too - Martin

Ice melt in the Antarctic will cause a noticeable shift in
the earth's center of gravity. That and ice melt will bring
sea levels up more so in some areas than others. Dan

 

[Q.G.]

That tiny bit of ice on that thin outer crust of earth, shifting earth's center of gravity noticeably?
Shows us how extremely sensitive the machines are they can produce nowadays.