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Lifting power of Soda Bottles**

Metric to English lifting power

Gallons to lifting power

1 & 2 liter bottles

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How much air does it take to float things?**

Most American bottles have their volume written on the label in milliliters (ml). The metric system was founded on a pure-water-base. ("Fresh" water is pretty close to "pure" water.) Each **1 ml = 1 cc = 1 gram of pure water**. If a soda bottle says “**591 ml**” it means it will support 591 grams minus the mass (weight) of the bottle, according to Archimedes Principle. Plastic bottles don’t weigh much, so you should be able to hold up about **561 grams in fresh water**. (It should float that much in a lake.)

Salt water is a little heavier, so it should float: **604.75 grams = 1.333 pounds** per soda bottle of that size.

Seawater weighs **1.025 grams/milliliter** or **1 gallon of air** should lift **8.556 pounds in seawater = 3,880.9 grams = 3.88 kilograms**.

Clear as mud?

Add up all the displacements of all your bottles in the water, minus the weight of the bottles, and that’s how much your bottles should float.

**How to Convert:**

**Pounds to Kilograms, pounds/2.2 = kilograms**

Kilograms to Pounds, kilograms x 2.2 = pounds

**Example:** If a small soda bottle of air will displace 591 ml (ignoring the weight of the bottle) it will lift 591 grams. That equals, 0.591 kilograms (kilo stands for 1000,) times 2.2 equals, converts to, 1.3002 pounds.

**1 gallon of air** displaces, and thus will lift (minus the weight of the container,) **8.333 pounds in fresh water**.

**1 gallon of air** should lift **8.556 pounds in seawater = 3,880.9 grams = 3.88 kilograms**.

So a 35 gallon hefty garbage sack of air, in theory, should lift 291.66 pounds. However, it’s not good to stretch one, so only fill it about half full. So it could lift about 145 pounds. Whereas a 50 gallon Hefty Garbage Sack, filled about half full should lift about 214 pounds.
It’s hard to know how much your island will weigh, but if you know how much it sinks down into the water, you should be able to make a good guess. That’s how they measure ships.

**Thus:**

A **1 liter bottle of air** will float about **1 kilogram** or **2.2 pounds in fresh water**; or **1.025 kilograms** or **2.255 pounds in seawater**.

A **2 liter bottle of air** will float about **2 kilograms** or **4.4 pounds in fresh water**; or **2.05 kilograms** or **4.51 pounds in seawater**.

(Without subtracting the weight of the bottle.

**Example:**

My **591 ml** soda bottle weighs about **30 grams**.

So, it should hold up about **560 grams** or **1.2 pounds in fresh water, 1.23 pounds in seawater**.

With amounts this small, you have to round, so it's "about."

**Underwater:**

Underwater, air is compressible, so a soft flotation component, such as a Hefty Garbage Sack will be slightly smaller, but since you’re not filling it over half way, it may not matter. But if you’re going to use these bags for deeper water, such as salvage work, you have to allow for expansion of the air as it rises to the surface, otherwise it might burst.

Ping-pong balls will float too, but I don’t know their volume.

As I run across helpful information I’ll add it to this website.