Introduction: Solar Hot Air Balloon Message-in-a-Bottle

Picture of Solar Hot Air Balloon Message-in-a-Bottle
This is a hot air balloon made from trash bags and heated by the sun. Once airborne, it should stay up 'til the sun goes down or behind the clouds. Needless to say, it can travel a long, long way. Attached to it is a "message-in-a-bottle" asking anyone who might find it to email their location, just to see how far it flew. There's just something romantic about a message seeking out who-knows-whom in far away who-knows-where.

As a note, as boys, my brother and I lived on a tidal river in Florida. Walking the mangroves, we found a couple of messages-in-bottles that people sent. One came from another state. It said something like, "Send a postcard with your address and we'll send a present." My brother sent a note and sure enough they sent back a King James Bible (it was a "Fishing for Men" outreach project by a Georgia church). He still has that Bible. It was inspiring to think of how far that message had come and the path that it took. The magic of a message-in-a-bottle is to imagine, "Where will it go?" and, "Who will find this?"

Step 1: Materials and Tools

Picture of Materials and Tools


1. Trash bags -- They must be THIN, I used 0.6 mil but the thinner the better. Most quality bags are heavy, at least 1.0 mil. We want the cheap-O bags.
2. Tape -- I used regular masking tape. Likely scotch tape is okay too. Don't use the wide package tape though--too heavy.
3. Thread
4. Pen and paper
5. Plastic bottle -- I actually had to get rid of the bottle because it added too much weight.

1. Scissors
2. Blow drier

Step 2: Layout and Taping

Picture of Layout and Taping

This may look harder than it actually is. To go with the pictures, I tried to sketch some diagrams. Just realize that it's pretty simple.

Get 4 bags and cut them open by cutting the bottom and ONE side. It'll unfold then to a big rectangle. Lay out all 4 opened bags like in the picture/diagram. Tape them together to make a huge rectangle.

STEPS 2 and 3
Fold the huge rectangle over then tape the two sides closed. You now have only the bottom untaped and open.

STEPS 4 and 5
Hold the center of the open seam and lift it open so that the points marked A & B in the diagram come together. Tape and seal off the last open seam.

Step 3: Write Your Message and Inflate It

Picture of Write Your Message and Inflate It

Get your message ready. Once it's inflated, it's go-time! I scratched the plastic bottle after it became clear that it was weighing down the balloon. I just rolled up the message, then tied it off with a piece of thread about a foot long. Essentially, the message asked for an email back to me simply saying where the balloon was found.

Just as a note, since this is a SOLAR balloon, so you'll want to do this on a bright sunny day.

Cut about 3 inches off of one corner. Just cut enough to shoot hot air in it from your blow drier. Simply start blowing hot air into the balloon. Be careful not to burn or melt the bags. The balloon will quickly take shape.

As soon as it's inflated, twist the opening so it closes, then tie your message onto it. Once inflated, I moved into the sunlight so the sun would start heating it up.

Step 4: Watch It Go!

Picture of Watch It Go!
Nothing much to say here, launch it and watch it go!

After floundering around a bit, it started to gain some altitude, bounced off some power lines and shrubbery, then finally got above the treeline. Then it was gone!

I intended to chase after it on my bicycle. I quickly saw that was pointless. Within 10 minutes, it was out of sight last seen heading north--still gaining altitude. It's hard to guess the distance, but I'd say 5 miles in 10 minutes (that'd make it 30 mph once it got up high).

Now, it's just wondering where it went, how far, and hoping that someone finds it and shoots back an email.


mentalman (author)2011-08-02

THis is TOO FUNNY a big argument over the moisture content of the air in tha bag BUT WAIT ! There's MORE .That bag can get caught in the JET ENGIONE of a plane. when that happens the plane will come down or land and They will read your message and know where you live. We used to set off huge bags with helium in them . and Like fools the bags had the company Logo on the side.
They were 10 feet long and we would watch them at the "Lunch Launch. But one day The cops showed up because they were getting in to the flight path of the Air port 15 miles away. We got 1 warning to stop. Next they would have put us in jail YEP that's fact.

srodocker (author)mentalman2011-08-05

you're a real d-bag, you know that?

KJ4ZVQ (author)srodocker2011-08-12

plus, if it gets in a jet ENGINE, in would likely be destroyed. might not even hurt the ENGINE.

shomas (author)KJ4ZVQ2015-07-14

Plastic bag versus super heated pressurized air plus jet fuel inside a jet engine with titanium blades?????? Lets say shredded and burnt only to become fuel for the engine and adding to the its thrust.

shomas (author)2015-07-14

The volume of 1 mole of any gas at slandered temperature and pressure is 22.4 liters.

1 mole of oxygen gas (O2) = 32 grams. 1 mole of nitrogen gas (N2) = 28 grams. 1 mole of water (H2O) = 18 grams.

In terms of density (O2) = 32G/22.4L; (N2) = 28G/L; and (H2)=18G/22.4L

Water vapor, at 18 grams a liter has a lower density than the two main components of our atmosphere. liquid water is is not governed by gas laws and has a density of 18 grams per milliliter over a wide range of temperature. You don't need to separate the compounds in water to determine its density, but you do need the atomic masses of the atoms that make up water to determine molar weight.

rimar2000 (author)2011-07-26


Damp air is lighter than dry air. Maybe you can inflate the balloon with your lungs (many persons, because it is a great volume) instead of the hair drier. That should give it longer scope/range.

csnowman00 (author)rimar20002011-07-28

Maybe you can get a spray bottle and 'spritz' the air going into your hair dryer. That possibly could make the air damp, especially if you put the heat on high.

devonfletch (author)csnowman002011-07-28

The water will make the thing too heavy to fly, and you'll be too dead to observe the effect.

shomas (author)devonfletch2015-07-14

The volume of 1 mole of any gas at slandered temperature and pressure is 22.4 liters.

1 mole of oxygen gas (O2) = 32 grams. 1 mole of nitrogen gas (N2) = 28 grams. 1 mole of water (H2O) = 18 grams.

In terms of density (O2) = 32G/22.4L; (N2) = 28G/L; and (H2)=18G/22.4L

The bigger issue is with air a few degrees above ambient temperature, how do you keep water in vapor form rather than in condensed form. The answer is that it can hold only as much water as 100% humidity for a given temperature and pressure. at 100% humidity, a drop in temperature will cause water to condense to smaller than 1/1,600 its vapor form.

skylane (author)csnowman002011-07-28

Incredibly DANGEROUS and stupid idea...
Your post should be removed
Spraying water into a hair dryer? surely you jest!

csnowman00 (author)skylane2011-07-28

as long as you don't spray salt water you should be fine. Saltwater conducts electricity more than tap water. Everybody knows that.

pdionne (author)csnowman002011-07-28

Distilled water would be the safest. Tap water has all kind of minerals and iron in it. Ever see rusty water? That's iron and it is conductive.

badcoconut (author)csnowman002011-07-28

Too Funny!!!....... true salt water does conduct better than tap water..... Tap water will still kill you ... maybe you will not be as dead with tap water as with salt water but dead is still dead :-)

pdionne (author)csnowman002011-07-28

HERE's your sign!!!

jester_rob (author)rimar20002011-07-28

just wondering how you came to the conclusion that damp air is lighter than dry air? 0_o

deitzgen (author)jester_rob2011-07-29

Air is about 78% Nitrogen (N2) , about 21% Oxygen (O2) and about 1% other gases. Nitrogen has a molecular weight of 14 so a N2 molecule has a molecular weight of 28. Oxygen has a molecular weight of 16 so an O2 molecule has a molecular weight of 32. given the ratios of air and the molecular weights of the components, air has a molecular weight of 28.6 (0.78 * 28 + 0.21 * 32 = 28.6).

Water is made up of two hydrogen and one oxygen atoms (H2O). Hydrogen is the lightest element and has a molecular weight of one. So a water molecule has a molecular weight of 18 (2 * 1 + 1 * 16 = 18). Water is a very light molecule and much lighter than the average weight of the molecules found in air.

as you can see above water vapor is lighter than air, and when the air is moist, water vapor displaces an amount of air (replacing heavier air with lighter water vapor), thereby making the moist air lighter. Of course the temperature and pressures must be the same for this to be true.

Included is a link to calculate weight of dry air, moist air and amount of water vapor in moist air.

devonfletch (author)deitzgen2011-08-01

Yes, water vapor is a little lighter than air, but when it condenses on the bag, which is cooler than the air inside, it turns to liquid water, which is hundreds of times heavier.

Paymeister (author)devonfletch2011-11-12

Yes, liquid water is indeed heavier than water vapor by volume, but you don't just add mass. You keep the same mass you had, but it's in a smaller package.

Here, you have X grams of water in the form of vapor inside the bag (if you do the trick he suggested). Once the surface of the bag cools below the dewpoint for that humidity, those same X grams will drop out of vapor form into liquid water on the inside of the bag. But you won't ADD mass - it will just be in a different form.

By turning the vapor into liquid the bag's volume will decrease (since X grams of liquid water is a lot smaller than X grams of water vapor - remember the capped steaming tin can demo in high school). Thus the total mass of the airship will still be there but the volume will have dropped, making it more dense (density being mass/volume), so it will lose bouyancy.

devonfletch (author)Paymeister2011-11-13

Well, yes, Paymeister, I should have said 'hundreds of times heavier than the same volume of air', which is what I meant.

rimar2000 (author)devonfletch2011-08-01

Yes, that is possible, but if the balloon is at full sun, is not as easy.

Paymeister (author)rimar20002011-11-12

Should have incorporated this into my post above: to get to the dewpoint you'll need to cool it a fair amount, which won't happen in full sun.

rimar2000 (author)jester_rob2011-07-29

It is not my conclusion, it is a fact. I am guiltless!

shomas (author)2015-07-14

The volume of 1 mole of any gas at slandered temperature and pressure is 22.4 liters.

1 mole of oxygen gas (O2) = 32 grams. 1 mole of nitrogen gas (N2) = 28 grams. 1 mole of water (H2O) = 18 grams.

In terms of density (O2) = 32G/22.4L; (N2) = 28G/L; and (H2)=18G/22.4L

The bigger issue is with air a few degrees above ambient temperature, how do you keep water in vapor form rather than in condensed form. The answer is that it can hold only as much water as 100% humidity for a given temperature and pressure.

broccali (author)2013-12-01

maby if you get it to carry a heavier load you cen hook
up a solar panel to a
motor with a propeller

gwarbeh (author)2013-05-15

Awesome idea! I have to try this some day. I wonder how big you could make it, and whether making it much bigger would enable it to carry a heavier load.

georion (author)gwarbeh2013-11-20

10 foot weather baloons carr very littlt weight.

Titanica-art (author)2013-01-14

The idea might be good, but I hate the fact that this plastic probably will end up in the ocean where it can be deadly for mammals or other sea creatures. Or it may end up somewhere in the nature which is also a bad idea.

georion (author)Titanica-art2013-11-20


foobear (author)2013-07-11

Sooo... did anyone ever find it?

bradley.waldron (author)2012-10-15

Innocent until proven guilty? sigh...

jack.spigack (author)2012-09-23

they can do what ever they want. if you are poor or dont have connections in the government and the state takes you to court and knows they will lose if they dont lie they will lie and are allowed to because they arent "under oath" see how that work? and your attorney will side with the state prosecutor to protect the state government. its something called the state claiming sovereign immunity and it works great with the state bar code of ethics to make the government employee pulling some scam right even when they arent. have you ever wondered why it is that government people when they harm a non government person gets off the hook on a technicality when it is clear they are guilty? the exception to this rule is if they government person is televised red handed in the act. true story even if its just video taped and not televised the government people will get off the hook oops i just made myself a target for pointing out the obvious

calebgeb (author)2012-09-09


Velin9 (author)2012-06-30

i made one but the wind blew it into a thorny bush: (.

Gazan869 (author)2011-08-02

Just wanted to pass on some info as “food for thought.”
I'm a deputy sheriff in southern California and we've recently had several training bulletins about people filling trash bags with various explosive gases. The training bulletins described these as “improvised explosive devices (I.E.D’s)” and described an incident where one of these exploded when several officers approached it. This particular device caused injury to the officers.
Now I know that this “device” is harmless and uses nothing more than air but I would point out that should a “over-zealous” police officer/deputy sheriff/state trooper find one of these with a name, address or some other way of finding out who released one of these, they might try to prosecute that person for making an explosive device. If the bag has become deflated, it could be said that the explosive gas had escaped and dissipated. It would then be on the maker to prove that it was filled with nothing more than hot air.
Now whether someone gets convicted of this is another matter but whoever made one of these would have to go through the ordeal of court and all that entails. Yes, most of us in law enforcement are level-headed, common-sense type people but we all know that there are some in Law Enforcement and in the court system that go by the letter of the law, not the spirit of the law. We see some of them in the news from time to time. And what if you get a jury that believes the prosecutor over your attorney.
Unfortunately, in this day and age, something as innocent as this can be turned into something entirely different. Just a word of advice.

Below are two links to video of what I would call individuals of lessor intellegence using something similar to this "device." These links were actually part of the training bulletin.

bazeemuth (author)Gazan8692012-01-15

Gazan, I get two things out of this posting:

1) You're a law enforcement official within the borders of the U.S. who thinks the burden of proof is on the accused.

2) You're a law enforcement official within the borders of the U.S. who would advise citizens not to pursue certain lawful activities because it might trigger an incompetent reaction from your fellow law enforcement officials.

I guess there's no big problem with (1) since you're not going to be passing judgement on anyone and there are people who do know the basics of the law running the courts. On the other hand (2) gives me pause, since your advice is essentially to avoid doing things that reveal governmental incompetence and the underlying (systematic?) misallocation of power to those who would misuse it.

Good information to have, in a way.

abarratt (author)Gazan8692011-08-16


I have to take issue with your comment,

"If the bag has become deflated, it could be said that the explosive gas had escaped and dissipated. It would then be on the maker to prove that it was filled with nothing more than hot air. "

Given that its possible for trash bags to end up all over the place, do the police really waste time treating them all as IEDs that have had the "gas dissipate".
Also, do you really thing that someone who has left a name tag on it, would do so if there was any nefarious intent.

Can you imagine, "Hey, if this IED didn't detonate properly, please call 1866 TERRORIST"


Gazan869 (author)abarratt2011-08-16

My only reason for posting what I did was to give anyone thinking of trying this some food for thought. I said that there is a possibility that someone could be prosecuted, given the training bulletins that have been going around. One more thing to think about is that if emergency services are sent out regarding a potential threat/explosive device/or whatever, the person who created the device or event, whether there was any ill intent or not, could potentially be charged for the costs of those services. I know with my jurisdiction, we submit a cost recovery for our services on any DUI related collisions. I also am aware that my department is pursuing cost recovery on an "open-carry" individual who called in a "man with a gun" call on himself.
I know that we're talking apples and oranges here, in regards to an inflated bag verses a criminal incident, but with the financial situation of the country, I don't see it as a great leap that cities/counties/states charging for the cost of law enforcement and/or other emergency service response. Heck, I know of some agencies that are going to start charging for law enforcement response to a traffic collisions. I'm not saying that I agree with it by any stretch, but it's been put out there and may be coming to a city/county near you.
Again, this is all just food for thought. It is best to think of the "worst case" of any situation before attempting it. If you plan for the "worst case" you might avoid it actually happening.

Paymeister (author)Gazan8692011-11-12

Gazan869, thanks for your service to the community by pinning that big target to your chest and running TOWARDS trouble instead of away from it. Yes, we all know that there are bad cops out there, but the vast majority are hardworking folks whose worst fault is letting the fertilizer they deal with every day color their view of people in general. I know: I was a schoolteacher and the few jerks in my class that took all my time and energy kinda colored my view of random kids for a long time. BTW - I taught in Southern California, and now live up in the hills, ten miles from the Appalachian Trail. You would take a pay cut of about 2/3, probably (ain't a war zone) but we need cops, too and the folks here are great.

Thanks for posting your comments - you obviously posted out of concern for Joe Instructablefollower and out of your concern for the wasted time of your brother officers called out on a 'dangerous trashbag' call.

To all the negative posters: please lighten up: he's not saying the *you* are jerks, just that some folks might overreact. He wants to protect you, for crying out loud, from overzealous cops in your area. Got level-headed folks out there in the country? Have at it. Live in Southern California or upwind from an airport? Might rethink it.

abarratt (author)Gazan8692011-08-25

your country is seriously screwed if the police feel the need to recover costs for chasing bin bags.

time to go after the real criminals.

a deflated bin bag, could have blown off the back of a garbage truck. People need to start applying some common sense.

xinistrom (author)abarratt2011-08-29

also, if this is really true, you can just frame some random person to get them in trouble ;)

akampen (author)Gazan8692011-08-04

Interesting to hear your take on Burden of Proof....I always thought that in free countries it rested with the state, not the individual.

zfolwick (author)akampen2011-09-05

don't forget... he's a cop too.

a little bit of power and they think they have a blank check.

Jaycub (author)akampen2011-08-06

Yeah no kidding, they can't put you in jail because they found a garbage bag with your name on it.

zfolwick (author)Gazan8692011-09-05

"It would then be on the maker to prove that it was filled with nothing more than hot air. "

It's a good thing that people are innocent until PROVEN guilty.

panzerfaust379 (author)Gazan8692011-09-03

1 bullet & a whistle I'll bet. Eh Barney.

Gazan869 (author)panzerfaust3792011-09-05

Well, now that you mention it, the town I work in is sometimes referred to as "Mayberry" and I've been call "Andy" a time or two since I've worked there for over 20 years.

panzerfaust379 (author)Gazan8692011-09-05


grt57 (author)Gazan8692011-08-21

I am winking and putting my tounge in cheek as I type this ok? But...

Every party needs a pooper, that's why we invited you...

Really I'm just kidding, please don't invoke the so called patriot act and come arrest me.



Gazan869 (author)grt572011-08-22


No offense taken. I've been doing this job too long (over 30 yrs and planning on "pulling the pin" next year) to get my feathers ruffled over stuff like that. Just ignore the black helicopters, tho. ;-)

Take care & stay safe.


srodocker (author)Gazan8692011-08-05

FYI, they sell kits for this at teachers stores.

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