48 uses for PET bottles.

Some of the best are towards the end, so have a good look.

1. Measuring volume of exhaled air.

Fill bottle with water, place cap on, place upside down in a basin of water, so that the bottle neck is submerged. Now remove the cap while it is still underwater. Blow air through a hose bent up and into the bottle, mark the edge of the bottle with a pen where the air reaches. This volume can be calculated by filling the bottle with water to this level and then pouring the water into a measuring cylinder or by weighing the bottle and subtracting the mass of the empty bottle (1 gram of water = 1 millilitre). You may need a big bottle for adults, I can nearly fill a four litre wine cask (out of the box) in one breath.

2. Loop, strap.

Sections of bottle, say strips 2cm wide by the circumference long, can be nailed to timber and used to support upside-down bottles, around the neck and around the circumference.

3. Rain gauge.

An inverted bottle with the base cut off. A neck section can be inserted, as a funnel, to reduce evaporation. Attached with loop/strap - see #2.

4. Wall-mounted pot plant holder.

An inverted bottle with the base cut off and a hole in the cap or no cap. Several in a vertical row could use the drips from the one above. Attached with loop/strap - see #2.

5. Terrarium.

I first saw this in 1980, when PET bottles were quite new to Australia.

6. Water Rocket.

Compressed air in the bottle forces out water, providing thrust. See the Danger notice if you don't know much about these.

7. Windmill, direction or speed indicator.

8. Submarine.

Maybe. Maybe a partly gravel filled bottle and the rest water filled could have a hole in the cap, alka seltzer could be added producing CO2 gas and expelling water so the bottle would gain bouyancy. Put it in the water, at first it sinks, then fills with gas and floats back up. The gravel would be at the cap end, with a small hole in the cap, gas accumulates at the base of the neck-down bottle, water leaves through the hole, unimpeded by the gravel.

9. Air supply for staying under water.

Be careful not to drown. Sand filled bottles could be weights to hold down the air filled bottles, a hose could be used like a snorkel. I wouldn't mess with pressurised bottles and my lungs, get a real SCUBA tank if you want to do this. Don't dump sand filled bottles in the sea.

10. Vertical extension for a fish tank.

An inverted bottle with neck removed could protrude above the water line. Or perhaps remove the base and hang the bottle by the neck with a string.

11. Reservoir to capture hydrogen gas made by hydrolysis.

Perhaps these could be linked by a thin hose so that a number of bottles could be filled simultaneously. ie. all bottles inverted in water, hoses filled with air between the tops of bottles down under the opening, would require some air in bottles and hoses to begin with.

12. Soggy newspaper receptacle.

Squash the paper in a bottle with holes in the bottom. Maybe two bottles could be placed on opposite ends of a spinning pole, centrifugal force speeds exit of water. You can burn the dried results as a fuel, if you insist on open fires.

13. A funnel.

14. An ant farm.

15. A closed environment for mould experiments on pieces of bread.

16. Gravity demonstration.

Can demonstrate that a falling water-filled bottle with a hole in the bottom will not lose water while accelerating under the influence of gravity. Cheaper than putting holes in perfectly good buckets.

17. To stop dogs pooing on lawns.

Water filled bottles often discourage dogs from relieving themselves in the immediate area. In Melbourne it is not unusual to see water filled bottles left lying on lawns.

18. Timber protector.

Timber beams may be kept dry when sections of PET bottle are tacked on top to provide protection from the weather. The tops of fence posts may be covered with round bottle sections, horizontal beams may be protected by straight sections from the bottle. This may be used to protect timber letterboxes from the weather.

19. Headlight protectors for cars.

Probably better than nothing, flatten out the cylindrical centre section.

20. Drip catcher.

With top cut off may be placed under taps to catch drips, providing a bowl of water for animals.

21. To put home-brewed beer in.

22. Mini compost heap.

23. Hourglass.

Two bottles may be connected by cutting holes in their caps and pushing the caps into either end of a film canister with the base cut off. Find the right sand/hole size combination to get an accurate time piece.

24. Whirlpool demonstration.

Connect bottles as for hourglass, with holes in cap as large as the neck of the bottle. One bottle is mostly filled with water. When inverted, the water will bubble into the lower bottle, if first given a spin, the water will fill the lower bottle much more quickly, due to air travelling up through the middle of the spiral.

25. Stained glass windows.

I don't know how this might be done, but coloured rockets have been made, so it is possible. Eucalyptus oil (and other substances) will clean label residue from PET bottles. Gary has a link about coloured rockets

26. Electrostatic motor.

Somewhere on the www I once came across an electric motor than was powered by the high voltage difference than exists between the ground and high in the air (5000V or so). A weather balloon was put in the air with a multi-needle charge gatherer (like a metallic echidna), a thin wire ran back to the ground. I don't know that there is any practical application, but it was interesting, and made mostly with PET bottles.

27. Crumple zones for road barriers or telegraph poles.

A lot of bottles could placed around solid objects, maybe water filled with an easily breakable cap. They could be enclosed in plastic roofing sheeting like a large cylinder. A cheap solution, probably better than nothing.

28. Crumple zone in your own car.

Fill the boot (= US trunk) up with empty bottles if you are worried about rear impacts, or the front in your VW beetle or Porsche. I can see this being a trend amongst Porsche drivers. I advise you seek the professional advice of an automotive engineer on this one. I don't know whether cap on or off would be better.

29. Fibre manufacture.

This is done commercially, I've heard of sleeping bags and coats having filling made from PET bottles. I don't know whether they mix it with something or whether there is any flammability problem. Also I think ropes have been made from old PET bottles. Randy Crawford tells me clothes and carpets are made from PET bottles in Canada

30. Sinking boat prevention.

A few well placed and securely attached PET bottles may be useful.

31. Pressurised spray gun.

It could also make a water pistol. Randy Crawford believes water rockets got started, way back in 1983, as a more out of control spray gun. He read about it in a magazine, you'd better ask him about it. rcrawfor@direct.ca

32. Emergency fire lighting.

A water filled bottle can be used like a lens to concentrate the sun's rays. I've got as far as getting things smoking. If you can't get the fire happening, you'd better put a message in the bottle and throw it in the sea.

33. Thermal mass / fire retardant.

Water filled bottles could be enclosed in wall cavities, providing thermal mass to buildings. In the event of fire they would burn open, releasing water. Lying them in a hexagonal honeycomb way would work well.

34. Raft manufacture.

Join a lot together and go for a sail. A wooden platfrom may provide some rigidity.

35. Rocket cars.

Like a flying rocket, but lies horizontally. Fill more than half full with water so the water is above the nozzle, the acceleration seems to ensure all the water is expelled by being forced against the rear of the bottle. In Japan these have been made with remote control cars. I think they could also be made in a more low-tech way. Less thrust is required than for a flying rocket.

36. Bird feeder.

Dave Johnson tells me a device is sold in the US that screws on to the bottle neck and turns it into a bird feeder. Perhaps with a cap with a hole as big as the neck, pushed into a film canister with a hole(s) in the sides near the base, then the base of the canister screwed on a platfrom, a do-it-yourself version could be made.

37. Bouy / Flag float.

Two bottles, one partly filled with sand, the other brightly painted, connected by a cord, used as a bouy and it's weight, a diver's flag could be attached.

38. Weight.

Filled with sand and tied to the edges of a tarp to hold it down in the wind.

39. Mini-greenhouse.

Cut the neck from the bottle and turn it upside down, stick it over small plants. This is called a "cloche" in Canada.

40. Ice pack.

Freeze water in them to put in the picnic cooler or wherever, as the ice melts it does not make a mess everywhere.

41. Flying insect traps.

Randy Crawford uses these to catch insects for his frogs. He uses two types of traps and has described them as follows:

Trap 1 is a bottle with the top 1/3 cut off, trimed so it makes 3 legs (holes for the flies to access the bait which is put under this affair) and inserted into the other 2/3. After the flies feed they always leave by taking off and flying upwards, thru the funnel and into the main chamber. They are too stupid to try to get out the hole, always trying to fly up. Yes, it really works.

Trap 2 has short pieces of tube inserted in the sides, pointing down. The bait is put in the bottom, the flies enter thru the tubes, and again are too dumb to get out that way. They actually sell a trap in Canada very similar in design (no 2 litre bottle, though).

42. Driving piston engine.

Dave Johnson told me about this. Commercially manufactured engines are made for model aircraft, the bottle contains compressed air which drives the engine to turn a propeller or whatever you connect it to.

43. Slow release watering system.

In Australia in the mid 1980s there was sold a screw on spike with holes in it. The idea was to have a water filled bottle and stick the spike into the ground near a young seedling so the water was released gradually. Probably a small hole to admit air in the base of the bottle would help.

44. Standard masses / density demonstration.

Fill bottles with appropriate amounts of water or sand or whatever to make a standard mass for use on a simple balance scale. This could give school students familiarisation with different mass amounts. You could also play guess the weight. Bottles filled with different substances, eg. rice, water, sand will demonstrate the concept of density, bottles made to be the same mass with different volumes of various substances are also a way of demonstrating density.

45. Candle-stick holder.

Cut the bottle a few inches below the screw-fitting. A candle can be stuck in the bottle neck, one way it can stand on a table, the other way it can be hand-held and will prevent dripping wax hitting the user's hand.

46. Aquarium CO2 generator.

Half fill bottle with water, add sugar and teaspoon of yeast. Hose in hole in cap allows CO2 to escape and be bubbled into aquarium.

47. Thermometer.

Like #46 but completely fill bottle with water, stand upright. As temperature increases the water expands and moves up the hose.

48. Expanding/contracting gas demo.

Run hot water over the outer surface of empty bottle, with lid off. This heats the air inside the bottle, causing it to expand. Now screw the acp on tight, remove from hot water, as the bottle cools the air inside also cools and contracts, the greater pressure outside pushes the sides of the bottle in. Can be done in reverse also, ie. heat with cap on, sides of bottle become more rigid, harder to push in makes different noise when tapped.

Any more? Please let me know. All comments appreciated.