Boiling Water Bath or Pressure Canning? What's the Difference?

Boiling Water Bath Canning
Boiling water bath canning is a method of home canning in which sealed jars of food are immersed into a pot of boiling water for a preset amount of time. There are a few universal rules to water bath canning, but not all foods get treated the same. 
For high acid or high sugar foods only:
- Fill jars to within a half inch of the rim of the jar with hot food or hot liquid.
- Check for air bubbles trapped under the surface of the food or liquid.
- In the case of pickles or other free floating food, a butter knife is handy to knock air bubbles loose.
- Removing air bubbles allows the air to escape the jar during canning which gives you a better vacuum.
- Apply lids and rings finger snug, not tight.
- Place jars into the boiling water and make sure they are covered by a minimum of 2 inches of water.
- Put a lid on the canner or pot to help hold in the heat.
- Start the timer when the water comes back to a full boil.
- When the time is up, turn off the heat and wait until the water stops boiling.
- Remove the jars from the water bath and set them aside for two minutes.
- After a minute or so, tighten the lids fully to “complete” the seals. A silicone oven mitt is a good tool for this purpose.
- This step is unnecessary, but greatly increases the chance that your jars will seal.
- Place the finished jars aside at a minimum of one inch apart to cool.
- Within a couple minutes, you should see and hear the first jars sealing. (Listen for the "ping" of a successful seal!)

Pressure Canning
If you are going to get food poisoning, it is likely to be from low acid and low sugar home canned foods that were improperly preserved. This doesn't mean not ever to even try pressure canning, it means to follow the tried and true guidelines. If you do this, you won't have any problems and you’ll love the results! Pressure canning MUST be used when preserving food that doesn't contain enough acid or sugar to kill the worst bacteria. Also, pressure canning relies totally on heat to kill the bacteria spores that are almost certainly found in the food.
- Most pressure canners come with an instruction manual, which will help a lot with the details.
- Depending on the type of canner you have, you’ll want one to two inches of water in the bottom to begin with.
- Distilled or rain water is the best because it leaves no calcium or deposits on your jars. These are sometimes very difficult to remove.
- If you want to use tap water, add a little vinegar to avoid these water deposits to some degree.
- Here's one way that pressure canning differs from water bath canning: the jars don't have to be completely submerged. 
- Now is a good time to preheat the canner, but make sure it isn’t sealed so that it builds up pressure yet.
- Put hot food and or liquid into hot jars to within a half inch of the jar rim.
- Check for air bubbles trapped under the surface of the food or liquid.
- In the case of green beans or other vegetables, a butter knife is handy to knock air bubbles loose from around the food.
- Put lid and ring on and tighten it to finger snug, not tight.
- Put the jars of food into the canner and apply the lid.
- It’s very important to turn the heat up high at this point and allow the canner to vent steam steadily.
- Once the water begins to boil, it usually takes 10-20 minutes for the steam to force out any remaining air in the canner.
- You’ll notice the air escaping the canner going from white to clear even though it is blowing air out the entire time.
- This means that steam is replacing air inside the canner, which is important.
- Steam will give you a more accurate pressure reading and it cooks the food more completely. 
- When it blows out steam constantly, it’s time to apply the weight and build up pressure.
- When the pressure reaches (a minimum of) 10 pounds, it is time to start the clock.
- At this time you must reduce the heat to just maintain 10 pounds (or more) of pressure.
- If you don't have a gauge, use the weight as your guide. If the weight is moving, you are at pressure.
- If you allow the canner to get too hot, the jars will lose liquid and might not seal properly.
- The pressure and time are both variable to your specific food and altitude.
- When the time is up, you simply turn off the heat and wait for the canner to cool down and de-pressurize all on it’s own.
- Pressure decreases as the temperature decreases, reducing pressure prematurely will cause big problems for your efforts.
- If you manually release pressure at this point, you could break jars or force liquid out of the jars.
- When the pressure is zero (between 30 and 90 minutes), you can begin to check your canner.
- Start by lightly jostling the canner weight to see if the pressure is gone.
- If the canner still has pressure on it, leave it for another 10 minutes or more to cool on it’s own. Don’t get in a hurry.
- When you are very sure the pressure is gone, slowly open the canner lid until it is loose and peek at your jars.
- The jars will still “boil” for quite some time, which is normal, but taking the lid off too quickly could result in fluid loss or worse.
- Allow them to cool for a few minutes with the lid loosely attached, this will help cool the jars more slowly than fully open.
- You should be able to safely remove the jars no more than 20 minutes later.
- Many times, the jars will start sealing right inside the canner, which is normal.
- Remove the jars and wait a minute or so before “completing” the seal by tightening the lids firmly.
- This step is unnecessary, but greatly increases the chance that your jars will seal.
- Set them an inch or more apart to cool and you are done.


*From www.survivalistboards.com