EXPERIMENTAL GLASS BLOWING

Boys, glass tubes are made in the sizes shown in Fig. 2, and in larger sizes. You will use sizes 2, 4, and 6 in the followingexperiments.

FIG. 2SIZES OF GLASS TUBING

Hold a piece of No. 2, with both hands, in the flame of the alcohol lamp, and turn it constantly (Fig. 3). Do you find that when the glass becomes nearly red hot, it becomes soft and bends easily?

FIG. 3HEATING GLASS TO SOFTEN IT

Take the tube out of the flame, bend it into any shape you wish (Fig. 4), and allow it to cool. Do you find that the glass hardens when it cools and retains the bent shape?

Heat the tube near the first bend, turn it constantly, take it out of the flame, and make another bend.

Repeat this and make all kinds of fantastic shapes.

Place all hot glass on the cooling blocks, not on the table.

Glass is used in many, many ways by the human race; for example, to make bottles, tumblers, window glass, and so on, andall of these uses depend upon the facts which you have just illustrated, namely, that glass becomes soft when heated and hard when cooled again.

FIG. 4BENDING GLASS

The wick should be cut straight across and should project above the wick holder about ⅛ inch (Fig. 5), or a little more if you require more heat. Burn wood alcohol or grain alcohol, because they give flames without soot or smoke. Fill the lamp to within a ½ inch of the top only; it will burn one hour. The hottest part of the flame is not down close to the wick, as most beginners suppose, but up just beneath the tip.

FIG. 5THE LAMP

Buy your alcohol at a drug store in quantities of one pint or more. When you are through experimenting for the day pour the alcohol from the lamp back into the pint bottle and cork the bottle tightly. Alcohol left in the lamp gradually evaporates and is lost.

Do not let the lamp stand with alcohol in it for any considerable time—overnight for example—because fuel alcohol contains water and when it evaporates from the wick, the alcohol evaporatesfirst and leaves the water in the wick. Then when you try to light the wick again, you will find that you cannot do so, because, of course, water does not burn. If this happens to you, take the wick out, dry it, and start the lamp again.

FIG. 6MAKING A SCRATCH

It is perfectly safe to use kerosene in the lamp, but it gives a very smoky flame which deposits soot on the glass and fills the air with soot particles. Your mother will object very strenuously to this because the soot particles settle and blacken everything. Burn alcohol only, at least in the house.

FIG. 7BREAKING THE TUBE

Cut off a six-inch length of No. 2 as follows: Lay the tube flat on the table, mark the six-inch length and draw the file across the tube at this point, pressing hard enough to make a good scratch (Fig. 6). Grasp the tube with both hands near the scratch, as in Fig. 7, pull apart and bend slightly. Do you find that the tube breaks across easily?

Repeat this with No. 4 and No. 6 tubes.

Experiment 3. To make the edges smooth.

FIG. 8MAKING THE EDGES SMOOTH

Hold one end of the six-inch piece of No. 2 in the tip of the flame (Fig. 8), and turn constantly until it is just red hot. Take it out and let it cool on the blocks. Do you find that the edges are smooth?

Repeat with the other end.

Repeat with both ends of the six-inch piece of No. 4.

If thick glass is heated quickly it may crack, because the hot exterior expands more quickly than the cooler interior and produces internal strains.

FIG. 9THE BLOWPIPE FLAME

The No. 6 tube is comparatively thick and should be heatedgraduallyas follows: Hold the end in the flame for about 1 second, then withdraw it for about 1 second; hold it in the flame again for 1 second, and withdraw it for 1 second. Repeat this eight or ten times, then hold and turn it in the flame until red hot.

Smooth both ends of the No. 6 piece in this way.

Hold the small end of the blowpipe just inside the flame at one edge, about ⅛ inch above the wick (Fig. 9), and blow air through the flame parallel to the top of the wick.

Keep your mouth closed on the blowpipe,breathe through your nose, andpractice keeping a steady stream of air going for a long time. You will be able to do this with a little practice.

Do you observe that the blowpipe flame is pointed, also that it is made up of a pointed cone inside and a lighter-colored cone outside? The hottest part of the flame is inside the outer cone just beyond the point of the inner cone.

FIG. 10CLOSING ONE END OF A TUBE

The blowpipe flame is hotter than the lamp flame because the heat of the burning alcohol is concentrated at one point by means of the air blast, and because the alcohol is more completely burned by the extra air.

Hold one end of a piece of No. 2 tube in the blowpipe flame (Fig. 10), turn it slowly, and heat until the end closes. Does it close nicely?

Close one end of a piece of No. 4 in the same way.

You can close No. 6 tubing in this way, but it leaves a large lump of glass which may crack on cooling or on reheating. You will practice closing No. 6 tubing later.

The “why” of it

The glass becomes soft when heated because it becomes almost a liquid, and if it is heated sufficiently it becomes entirely a liquid. In this respect it acts very much as pitch, rosin, and wax act when heated by the sun or by a fire.

FIG. 11MAKING A GLASS BUBBLE

The end of a glass tube becomes smooth, or closes entirely, when heated, for the following reason: The surface of any liquid tries to take the smallest possible area (this is explained in detail under “Surface Tension” in the Gilbert book on “Experimental Mechanics”), for example, a small particle of water takes the shape of a drop, a sphere, and the surface of a sphere has the least area for a given amount of water. Now when the end of the glass tube is heated it becomes a liquid, and the surface of this liquid contracts the glass into a smooth rounded surface of least area. If the tube is heated still more, the surface contracts still more and closes the end.

Smooth one end of a piece of No. 2 tube and allow it to cool. Close the other end in the blowpipe flame, turn it slowly, and heat until it is very hot. Take the tube out of the flame, put the smooth end into your mouth quickly, and blow as hard as you can (Fig. 11). Do you get a fine big glass bubble which bursts with a pop?

If you get only a small bulb at the first trial, heat the end, and try again. Do you find that the bulb shrinks when heated but blows out again readily?

FIG. 12BLOWING A BULB

When you get a big bubble, place the bubble end of the tube on a cooling block and break all the thin glass away from the tube by striking it with the file or blowpipe. Then close the end and blow another bubble.

Repeat until you can blow bubbles easily.

Repeat with a piece of No. 4 tube.

FIG. 13A WATER BALLOON

Do you find that the thin glass of the bubbles shows colors, especially in sunlight, just as soap bubbles do? You boys who have had the Gilbert set on “Light Experiments” will know that these colors are due to “interference.” The colors produced by a thin film of oil on water are also produced by “interference.”

Close one end of the No. 2 tube in the blowpipe flame again and while it is still hot blow carefully into the open end until you have a bulb about ½ inch in diameter (Fig. 12). Now let it cool.Make a scratch with the file about ¼ inch from the bulb, break the tube at this point (Fig. 13), and smooth the rough edge.

FIG. 14THE BALLOON SINKS AND RISES

Put the bulb in a tumbler of water. Does it float? If not, make another balloon with a larger bulb.

Find a large bottle made of clear glass, the neck of which will fit your solid rubber stopper.

Fill the bottle with waterto overflowing, insert the balloon, and then the stopper.

Now press down hard on the stopper. Does the balloon sink in a most magical manner (Fig. 14)?

Release the stopper. Does the balloon rise in an equally magical manner?

FIG. 15A BALLOON RACE

Make another water balloon. Put the two balloons together in the bottle filled to overflowing with water.

Insert the stopper and press down hard. Do the balloons sink (Fig. 15), and does one sink more quickly than the other?

Release the stopper. Do the balloons rise, and does one rise more quickly than the other?

The most buoyant balloon sinks last and rises first.

The “why” of it

FIG. 16DRAWING A THIN TUBE

You boys who have the Gilbert set on “Hydraulic and Pneumatic Engineering” will know the “why” of the last three experiments. Any body floats in water if it is lighter than an equal volume of water, and it sinks if it is heavier than an equal volume of water. Water is practically incompressible but air is very compressible: thus when you press down on the stopper, you force water into the balloon and compress the air in it; when you release the stopper, the compressed air in the balloon expands and drives the water out. When the weight of the balloon and the weight of the water in it are together greater than the weight of water displaced by the balloon, the balloon sinks; when they are less, it rises.

Hold a piece of No. 2 tubing in the lamp flame and turn it constantly. When it is red hot and soft,take it out of the flameand pull your hands apart until the tube is stretched ten or twelve inches (Fig. 16). Is the tube in the shape shown in Fig. 17?

FIG. 17A GLASS TUBE STRETCHED

Allow the tube to cool, break the large ends away from the thin tube, place one end of the thin tube in a glass of water, andblow into the other end to make air bubbles in the water (Fig. 18). If you can do so, it is a real tube.

FIG. 18AIR THROUGH TUBE

Does the thin tube bend easily and does it spring back when released?

Repeat the experiment with another piece of No. 2 tubing, but make the thin tube as long as you can.

Can you blow air through the thin tube, and does it bend very easily indeed?

Repeat with a piece of No. 4 tubing.

These thin hairlike tubes are called “capillary” tubes, from the Latin wordcapillus, meaning a hair.

FIG. 19WATER RUNS UPHILL

You have always heard that water runsdownhill, but you will now see it runuphilland remain there in a mostmagicalmanner.

Cut off 5-inch lengths of No. 6, No. 4, and No. 2 tubing, stand them side by side in a glass full of water (Fig. 19), and move them up and down in the water to wet the inside of the tubes.

Now look at the water level in each of the tubes. Is it above the level of the water in the glass, and is it higher the smaller the inside diameter of the tube, that is, is it higher in the No. 2 than in No. 4, and in No. 4 than in No. 6?

Now take the thin capillary tube which has the largest inside diameter, place one end in the glass of water, suck it full of water and blow it out. Now with one end in the glass of water notice quickly how the water rises inside the tube. Does it runuphillin a most magical manner (Fig. 20), and does it remain there?

FIG. 20WATER RUNS UP TUBE

Repeat this with your other capillary tubes. Does the water run uphill in each, and does it rise higher the smaller the inside diameter of the tube?

The “why” of this is explained in Gilbert’s “Experimental Mechanics” under “Capillarity.”

Common glass is made from three substances with which you are all more or less familiar; namely, sand, sodium carbonate (washing soda), and lime.

If sand and soda or potash are mixed and heated to a high temperature, they melt together and produce a glass which dissolves in water. This is known as “water glass” and it is used in many ways: to preserve eggs, to cement fire bricks, to make fireproof cement, and so on. If, however, lime is added and the mixture is heated to a high temperature, a glass is produced which is not soluble in water. This is the glass you know.

The three most common kinds of glass are: Venetian glass, made from sand, soda, and lime; Bohemian glass, from sand, potash, and lime; and crystal or flint glass, from sand, potash, and lead oxide.

FIG. 21SECOND STEP IN MAKING WINDOW PANES

FIG. 22IRONING THE CYLINDERS FLAT

HOW ARE THINGS MADE OF GLASS?

The glass mixture is heated to a high temperature in fire clay pots or tanks in large ovens. The surface is skimmed from time to time and the heating is continued until all air bubbles have escaped from the mixture, usually about three days.

The glass is now quite fluid and it is allowed to cool somewhat until it is viscous; then the objects are made by blowing, pressing, or rolling, as described below.

The finished articles are finally “annealed,” that is, they are placed while still hot in a second hot oven, which is then sealed and allowed to cool slowly, for four or five days or for as many weeks, according to the kind of glass.

If a glass object cools quickly, it cools more rapidly on the surface than in the interior. This produces a condition of strain in the glass and the object may drop to pieces when jarred or scratched. This condition of strain is avoided by allowing the objects to cool very slowly, that is, by annealing.

Window glass is blown in exactly the same way as you have blown glass balloons; the process is illustrated in Fig. 1.

The glass mixture is heated for about three days in fire clay pots and is allowed to cool until it is viscous. The glass blower then attaches a lump of the viscous glass to the end of a straight iron blowpipe about five feet long and blows a bulb. He then reheats the glass and blows a larger pear-shaped bulb and in doing so rests the glass on a pear-shaped mold of charred wood (see center of Fig. 1). He again reheats the glass, holds the pear-shaped bulb over a pit, and blows a long cylinder (see left of Fig. 1).

The ends of the cylinder are now cut off and the edges are smeared with molten glass to prevent splitting (see right, Fig. 21). The cylinder is next cut lengthwise with a diamond(center, Fig. 21), and is placed in a second hot oven, where it is ironed out flat (Fig. 22).

FIG. 23BOTTLES BLOWN IN A MOLD

The flat sheets are finally annealed in a third oven for a number of days and are then cut into panes, sorted, and packed.

GLASS TUBES

FIG. 24ROLLING PLATE GLASS

The glass tubes with which you do the experiments in this book are made in the same way as window glass up to the stage of blowing the cylinder; then the blower’s helper attaches an iron rod to the opposite end of the cylinder (see right of Fig. 1), and the blower and helper walk backward away from each other to pull the cylinder into a tube. Of course, they use a small amount of glass to make small tubes, and larger amounts for large tubes.

Many articles of glass are made by blowing the glass in molds. Bottles are made in this way (Fig. 23), and large machines are now in use which mold many bottles at one time in this way.

Many articles are made by pressing glass into molds, that is, the molten glass is poured into molds and is pressed against the sides of the mold by means of a plunger. Imitation cut glass is pressed in this way.

The large sheets of plate glass used in store windows are not blown, but rolled. The molten glass is poured from the fire clay pots upon a cast-iron table and is rolled flat by means of a large iron roller (Fig. 24). The glass is then in the shape of plate glass, but is rough on both sides. It is annealed for a number of days and then is ground smooth on both sides, first with coarse emery, then with finer and finer emery, and is finally polished with rouge. The result is the beautifully polished plate glass we see in large windows.

The United States and Great Britain made great strides in the manufacture of optical glass during the war and there are now many kinds on the market. They are used in making the lenses, prisms, and mirrors for optical instruments.

Optical glass is made in much the same way as ordinary glass,but great care is taken: first, to see that the materials are pure; second, to stir the glass constantly, as it cools from the molten to the viscous state, to make it as uniform as possible; and third, to cool it very slowly in the annealing process, to avoid strains.

FIG. 25A POLLYWOG

An entirely new glass has been placed on the market in quantity in recent years. It is made by melting very pure quartz sand at a temperature of 3000° F. and cooling it fairly rapidly. It has the very valuable property of expanding and contracting very, very slightly when heated and cooled. Thus there is practically no internal strain set up when it is heated or cooled quickly and it does not break. It can be heated red hot, for example, and then plunged into cold water without breaking. It is probable that this glass will be in universal use in a very few years.

Smooth one end of a piece of No. 2 tube to put in your mouth, close the other end in the blowpipe flame, take it out and blow a bulb about ½ inch in diameter.

Allow the bulb to cool, then heat the tube about ¼ inch from the bulb and draw it out into a thin tube. Now bend the thin tube at right angles near the bulb and break it off (Fig. 25).

Place the bulb in water. Does it float? If not, blow another with a larger bulb.

Experiment 13. Magic.

FIG. 26ACROBATS

Place the pollywog in a bottle filled to overflowing with water, insert the solid rubber stopper, and press it down hard. Does the pollywog sink?

Now release the stopper quickly. Does the pollywog turn somersaults in a most magical manner (1, Fig. 26), and also rise?

Make one or two more pollywogs, place them all in the bottle together (2, Fig. 26), and entertain your friends with a pollywog circus.

The pollywog sinks when you press down on the stopper because you compress the air in it and force water in until it weighs more than the water it displaces.

FIG. 27DANCING POLLYWOGS

The pollywog rises when you release the stopper because the compressed air drives the water out until the pollywog weighs less than the water it displaces.

The pollywog turns a somersault because the water rushes out sidewise in one direction and forces the nozzle in the other direction.

Air may escape from the pollywog when it is turning a somersault; if so, water will take its place, and may make the pollywog too heavy to float. You can restore its buoyancy by sucking out the water.

FIG. 28DRAWING GLASS SPIDER-WEBS

Make a pollywog as in Experiment 12, but bend its tail twice as shown in 1, Fig. 27; the nozzle is at one side and points sidewise.

FIG. 29THE SPIDER TRICK

Put it in the bottle full of water, then press down and release the stopper. Does it sink and rise, and does it also whirl around most beautifully as it rises?

Make another pollywog (2, Fig. 27), but bend its nozzle in the opposite direction. Does it whirl in a direction opposite to that of the first pollywog?

Put them in the bottle together and treat your friends to a pollywog dance.

The pollywog whirls because the water rushes out of the nozzle in one direction and forces the nozzle in the opposite direction.

Experiment 15. To make glass spider-web.

Heat the end of a piece of No. 2 tube in the blowpipe flame until it is melted and very hot. Now touch the end of another piece of glass to the melted glass, remove from the flame, and quickly pull the two pieces apart as far as you can (Fig. 28). Do you find that you have pulled part of the melted glass out into a very fine glass spider-web?

Repeat, but ask a friend to touch the second piece of glass to the first and run away as fast as he can.

Do you get a much finer spider-web?

Is the glass spider-web fairly strong and very flexible?

FIG. 30ATTACHING A HANDLE

Attach an imitation spider—or the dead body of a real spider—to the end of the glass spider-web and surprise your friends, as shown in Fig. 29. The glass spider-web is much less visible than a thread for this purpose.

You can save glass in many cases by attaching a short piece of glass to the piece you intend to work with, as follows: Heat an end of each piece in the lamp flame until red hot, press them together, remove from the flame, and hold until solid. The short piece then serves as a working handle (Fig. 30) for the large piece.

You closed small tubes in Experiment 5 by simply heating the end in the blowpipe flame. This method does not serve forlarge tubes, however, because it leaves a very large lump of glass which may crack on cooling or reheating.

FIG. 31CLOSING A LARGE TUBE

FIG. 32MAKING A SUBMARINE

Practice the following method of closing a large tube; first with a piece of No. 4 tube, and then with a piece of No. 6: Attach a working handle to the end to be closed, heat the tube ½ inch from the end in the blowpipe flame, turn constantly, and when soft pull apart until the tube has the shape 1, Fig. 31. Heat, turn, and pull the end away to leave the tube as in 2. Heat the end and blow out until it has the shape 3. The end is now closed and the glass has about the same thickness as the remainder of the tube.

Experiment 19. To make a submarine.

Close one end of a piece of No. 2 tubing as described above, but leave the end somewhat pointed (1, Fig. 32). Heat the tube on one side at a distance ½ inch from the end and blow a bulb about ½ inch in diameter (2). Heat the tube ¼ inch from the bulb, draw it down into a fine tube, and break off the tube, leaving a small hole in the end (3). Place the submarine in a glass of water, and if it floats it is complete.

FIG. 33THE SUBMARINE SUBMERGES

Fill a bottle to overflowing with water, insert the submarine open end down, insert the solid rubber stopper and press down hard (Fig. 33). Does the submarine submerge?

Release the stopper. Does the submarine rise and does it also move forward?

Turn the bottle on its side and release the stopper quickly. Does the submarine shoot forward at a great rate (Fig. 34)?

The submarine acts in this magical manner for the reasons given in Experiment 9. When you press the stopper in, you compress the air in the submarine and force water in until the submarine weighs more than an equal volume of water and it sinks. When you release the pressure on the stopper, the compressed air forces the water out until the submarine becomes lighter than an equal volume of water and it rises. The water rushing out through the opening exerts pressure backward on the water in the bottle and the reaction drives the submarine forward.

If your friends do not know about the little submarine, you can mystify them as follows: Tell them that submarines arejust like other fish; namely, they lay eggs, and the little eggs hatch out after a certain number of days (of course, your friends will know that you are only joking). Pretend that you found one of these submarine eggs, hatched it out in lukewarm water, and that you have trained the baby submarine to do some simple tricks. For example, that you have trained it to submerge, rise, and attack, when you issue the commands “submerge,” “rise,” and “attack.”

FIG. 34THE SUBMARINE SHOOTS FORWARD

Tell them to watch the submarine carefully and to notice that it takes in water and submerges when you issue the command “submerge.” Stand the bottle on the table, issue the command “submerge” and, while your friends are watching the submarine, press down on the stopper unknown to them.

FIG. 35A SUBMARINE BATTLE

Tell them to watch the submarine carefully again and to notice that it expels water and rises when you issue the command “rise.” Issue the command and unknown to them release the pressure on the stopper slowly.

Repeat with the command “attack” and release the pressure quickly.

Make a second submarine, place it in a large bottlewith the first submarine, turn the bottle on its side, and make the submarines manœuver by moving the stopper in and out.

FIG. 36FLARING A TUBE

Finally arrange them so that they are on the bottom, facing each other bow to bow, two or three inches apart (1, Fig. 35), and release the stopper quickly. Do the submarines try to ram each other (2, Fig. 35) in a most realistic manner?

FIG. 37AN AIR GUN

Heat the end of a piece of No. 2 tube until it is red hot, take it out of the flame, hold the flaring wire inside the end, and press outward gently while you revolve the tube (1, Fig. 36). Do you find that the end is flared out (2, Fig. 36)?

Take a full length piece of No. 4 tube and flare both ends slightly. This is the air gun (Fig. 37).

Now to make an arrow, cut off the lighting end of a match and insert a pin in the other end (Fig. 38).

FIG. 38THE ARROW IS SHOT PIN-END FIRST

Insert this arrow in the air gun and blow it out. Does it come out with considerable speed?

FIG. 39A SHOOTING MATCH

Draw a target on a piece of paper and hang it up, away from the wall or at the edge of the table, where there will be space behind for the arrows to pass through. Now shoot at the target with your air gun (Fig. 39). Do you find that the arrow makes holes in the target and sometimes goes right through?

The bull’s-eye of a target is usually 1 inch in diameter, the next circle outside is 2 inches in diameter, the next 4 inches, and the outer circle 5 inches.

Get up a shooting match and keep track of the score made by each.

If the bull’s-eye is cut anywhere by the arrow, the count is 5 points; a cut anywhere inside or touching the 2-inch circle counts 4 points; anywhere inside or touching the next two circles counts 3 and 2 points respectively.

The one who makes the highest score in five shots is the winner.

It is more sanitary if each shooter has his own air gun and arrows.

Experiment 26. Height and distance contest.

Go outside and see which of you can shoot his arrow to the greatest height and to the greatest distance.

Give each contestant five shots.

FIG. 40THE PEA SHOOTER IN ACTION

You can make fair estimates of the heights if you shoot up beside a building or tall tree.

FIG. 41BENDS

Take a full length piece of No. 6 tubing, smooth both ends and flare them out slightly. This makes an excellent pea shooter. Try it with peas. Do you find that they come out with great speed?

Make a target on a piece of paper, hang it up away from the wall or at the edge of the table, and shoot at it (Fig. 40). Do you find that the peas go right through the paper?

Arrange a match with your friends and keep track of the score as in Experiment 25.

A good bend has the same diameter in the bend as in the remainder of the tube (1, Fig. 41). It is rather difficult to makebecause the tube tends to cave in on the inside of the bend (2) or flatten on the outside (3), or both.

FIG. 42A DRINKING TUBE

Make the bend as follows: Heat a piece of No. 2 tube about 2 inches from one end in the lamp flame, turn it constantly and move it back and forth endwise to heat a length of about 2½ inches. When soft, take the tube out of the flame, and bend the endsupwarduntil the angle is 90°.

If the bend is flat on the inside or outside, close one end of the tube in the blowpipe flame, smooth the other end and allow them to cool, then heat the flat side of the bend in the blowpipe flame and blow it out slightly. This makes the diameter of the tube at the bend equal to that of the remainder of the tube. Cut off the closed end, smooth the edge, and your bend is complete.

Make bends with No. 4 tube.

FIG. 43A SIPHON

Many times when there is sickness in the house, it is convenient to have a glass drinking tube (Fig. 42), through which the patient can drink without raising his head.

Make such a tube from a piece of No. 4 tubing. The short arm is equal in length to the depth of the tumbler; the long arm, or mouthpiece, is about 1 inch longer than this.

Cut off a piece of No 4 tubing 8 inches long, maketwo right-angled bends about 1 inch apart at the center, smooth both ends, and your siphon is complete (Fig. 43).

FIG. 44A SIPHON

Put one arm of the siphon in a tumbler of water and suck air out of the other end. Does the water start running and does it continue to run in a most magical way (Fig. 44) until the water is below the end of the siphon in the tumbler?

FIG. 45FROM THE HIGH LEVEL TO THE LOW

Fill the tumbler with water again, start the water running, put the outer arm of the siphon in an empty tumbler, and stand both tumblers on the table (Fig. 45). Does the water run up one arm of the siphon and down the other into the empty tumbler? Does it stop running when the levels are the same?

Stand the first tumbler on a book. Does the water run again and stop when the levels are again the same (Fig. 46)?

Place the lower tumbler on the book and the upper tumbler on the table. Does the water now run in the opposite direction until the levels are again the same?

Raise one tumbler a foot or so above the table. Does the water run up over the edge and drop into the second? Now before the upper tumbler is empty, lower it in such a way that an arm of the siphon is in each tumbler, and raise the second tumbler. Does the water now run in the opposite direction?

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