The Tea Bag Phenomenon

The air in the bag is at room temperature. As the hot boiled water covers the tea bag, the air in the bag is heated. Then the pressure of the air increases. Secondly, the water covers the bag and the surface tension of the thin layer of water forms a seal on the tea bag holding the air in the bag. The result is the hot air pressure in the bag causes the bag to inflate.

Not only that, the tea itself expands. If you make a pot of tea the 'proper' way, the tea you take out on emptying the pot is a lot greater in volume than the dry tea you put in.

Then there's the question of out-gassing.

agree the gas generation from tea that high temperature is causing.

I do not totally share that tea itself is increasing by termal expansion, so shoud do the paper too: rather i would say that the dry leaves of tea are adsorbing water and unroling so the total increase of volume is a measurable appearence rather than real.

Query no.2:

• Why does the bag centre upon the jet?

I was going to say 'Bernoulli' then checked myself thinking this was only applicable to compressible flow. Quick look at Wiki seems to suggest his theorem can also be applied to liquids.

Bernoulli is used in all fluid flow applications (liquid or gas). Bernoulli is an extremely versatile formula. Remember though, if you give bernoulli junk, he will give you nothing in return!

COLD water also makes the tea bag float. But not as well. why: Tea is somewhat poreous as well as being less dense than water. So it would float with or without the bag. The bag actually helps keep out water making the whole float even better.

Its the blowing the ping pong ball thingy that you get in the Christmas crackers!

Or the fun fair water jet with a ball staying the flow....bernoulii and all that.

Beckham curling the ball, faster airflow on one side, isn't it..oh.. piles of sweaters for goal posts..don't they?..oooh suits you sir!

When's my Indian Takeaway coming?

It's the same reason that the wad of tissue paper in the toilet always moves toward the stream when your taking a leak - to splash and make a mess!

The jet of water breaks thru the surface tension of the water and by gravity forces its way thru and into the a lower levels, this creates a vacuum behind it which in turn sucks the surroundings with it.

But water on the surface is most able to move and so more of it goes into the vacuum , (along with that anything that is floating). WHy: Becasue the water at the surface has less pressure on the air side holding it in place so there is less friction to overcome.

Thats why surface ships can move faster than subs for same amount of energy expended.

BUT the tea bag has enough floatation inside from the heated air to overcome the downward force of the vacuum and so oscillates in the jet (stays centered almost on the jet with some up and down and side to side oscillation as the forces compete).

IE when a ship sinks it sucks surrounding things on the surface (like pieces of wreakage, etc ) down with it.

Why does the bag centre upon the jet?

Water flows through the bag and down to the bottom of the mug. Because the water can't continue down and more water is coming in, it flows to the sides and then up the sides. When it has gone up as far as it will go the pressure of more water coming in will push it back towards the center and pushes the tea bag with it.

Something similar happens in the atmosphere. Sunlight heats the ground at the Equator, and the ground heats the air. The air rises and expands towards the poles. At the poles the air cools and sinks back to the ground. The air then spreads back towards the Equator where it heats up and rises again.
This is a general explanation. The air over the Equator rarely travels all the way to the poles. The rotation of the Earth is also a factor. For more detail, look up global atmospheric circulation or Hadley cells in a meteorology textbook or other reference source.

You probably want the bag to stay under the jet as this gives maximum water flow through the tea. Increased water flow means more flavor.
I make tea a gallon at a time for iced tea. I start with two quart-sized bags and a half-gallon pitcher. I twirl the stings of the bags together to keep the bags close to each other. I hold the tags under my thumb with the bags resting against the side of the pitcher near the bottom. I hold the pitcher so the bags are under the tap when I run hot water into the pitcher at a fast speed. Then I dunk the bags 100 times and let it sit for about half an hour.

Heat and motion are the keys to unlocking flavor from tea. Because I don't boil my water, I make up for it with motion. My tea is plenty strong enough for me.

Heres my formulai for quick 5 minute easy ice tea making for either half or full gallon. (forget dunking 100 times, tedious). First put one big or 4 small tea bags into coffee maker ( you don't need filter since they are in bags. Then brew one half pot of hot tea (usual method as for coffee). Then pour hot concentrated tea over pitcher full of ice. Bawalla ! You're done!! Patent pending.. lol

Oh yes if you want sugar in it .. put it in either with the tea bags in the coffee holder or put in coffee pot . Either way mix sugar while tea is hot.. then pour over ice into pitcher.

If you want artificial sweetner.. same method or for some like sweet n low either before or after heat is removed.

Adjust procedure for more or less concentrations.

As a texan I have no idea what it could be.

Would you like, instead, to discuss the methane per patty ratio?

cr3

Because air trapped in the bag by preasyre expands as it heats.

I boil my water in an electric kettle unpressurised. I also live in a bungalow. Would it be alright if I put the Mug on the floor and stand on the table to pour the water? This is about .15 bar I could always go and find a tall building. But I suspect some one would take my Mug while I was climbing up with the kettle, and the water would get cold. So I think I will just agree with Del

Thank you to all contributors. The chimps' tea party will never be the same again!

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Can Post #1 and #7 give the name of the supplier of their teabags in the solid bags.

The ones available to me is all porous.

I need some of those to give to a friend who do not like the taste of the tea.

He then can use these bags without getting the flavour into the water.

Thinking of it the bag seems to inflate beyond the expansion of the leaves.

Does it have a lot of check valves?

Question 2

I think it rather stays in the centre because the water flows through the bag and will rise along the perimeter of the cup.

Does this phenomenon apply to herbal tea bags, square and ones with tags seem to act differently.

"Place circular tea bag [brand name witheld], of slightly smaller diameter, into the base of a cylindrical ceramic mug"

Better yet get a glass Cup of Tantalus for a real surprise ending.

I wish I drank tea to see what all the fuss was about! It makes my teeth squeak which inturn vibrates through my head! I can't stand the stuff, sorry! Any ideas on why this happens?

could it be your water?

No, I've lived all over the place and the same thing always happens! It only happens with tea bag tea, the infusions don't have the same effect, ie herbal stuff! I wish I knew what caused this effect!

I have the problem with baking powder and rhubarb (oxalic acid?), what do you take with your tea?

I don't drink it for this! but when I was younger, I tried it with milk and sugar, only milk, without milk, but still it made my teeth squeek! Does my head in!