From "The Complete Guide to Home Canning"
To
determine the elevation at your location click on the Topozone elevation
database
http://www.topozone.com/findplace.asp
Using
process time intended for canning food at sea level may result in spoilage
if you live at altitudes of 1,000 feet or more. Water boils at lower
temperatures as altitude increases. Lower boiling temperatures are less
effective for killing bacteria. Increasing the process time or canner
pressure compensates for lower boiling temperatures. Therefore, when you
use the guides, select the proper processing time or canner pressure for
the altitude where you live.
|
Pounds of Pressure |
Boiling point of water (F) |
Boiling point of water (C) |
Process
time |
Process Time Weighted Gauge (min) |
|
Sea Level |
212.0 |
100.0 |
10 |
10 |
|
1,000 ft |
210.2 |
99.01 |
10 1/2 |
15 |
|
2,000 ft |
208.5 |
98.03 |
11 |
15 |
|
3,000 ft |
206.7 |
97.05 |
11 1/2 |
15 |
|
4,000 ft |
204.9 |
96.08 |
12 |
15 |
|
5,000 ft |
203.2 |
95.12 |
12 1/2 |
15 |
|
6,000 ft |
201.5 |
94.16 |
13 |
15 |
|
7,000 ft |
199.8 |
93.21 |
13 1/2 |
15 |
|
8,000 ft |
198.1 |
92.26 |
14 |
15 |
|
9,000 ft |
196.4 |
91.32 |
14 1/2 |
15 |
|
10,000 ft |
194.7 |
90.39 |
15 |
15 |
- Actual boiling points are based on barometric pressure which is a function of altitude and changes with the weather conditions each day.
- To determine your real-time barometric pressure and the exact boiling point of water in your location visit http://www.biggreenegg.com/boilingPoint.htm
To compute the air
pressure (p) for each altitude, the formula used is p =
poe-ay
where
p = pressure in Pascals (Pa)
po = pressure at sea
level = 1.013x105 Pa
a = 1.16x10-4 m-1
y = altitude (m)
(see
Halliday & Resnick, Physics pp. 374-375, John Wiley & Sons, Inc.
(1978))
This formula assumes temperature and acceleration of gravity
are constant over the range of altitudes. T = 20 °C, and g = 9.8
m/s2.
