pressure canning at altitude (above sea level)

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    Pedro wyoming
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    For those of us that have headed for the hills already, we are accustomed to the altitude and do not consider the lower air pressure. We notice the bread has a different density and cooking spaghetti takes longer. We now know why there are instructions for “5000′ above sea level”.

    This past year, i have started canning. This pressure difference gets REALLY REALLY important when canning meat. The math formula is a bit complicated. I found the links below that can be used for any location if you know the elevation.

    http://www.westerndynamics.com/Download/boilingpointwater.pdf

    http://www.trimen.pl/witek/calculators/wrzenie.html

    First, look at the PDF and find your elevation and make a note of the pressure. Use any column below the “Barometer Reading” “Atmos. Pressure” boxes.

    second open the “trimen” link above and notice the box in the upper left corner. Put 14.7 in the upper left box and 100 in the upper right box. This is 14.7 psi and 100C boiling point of water at sea level.

    Next, enter the pressure from your elevation in the lower left box. Use the elevation that is higher than your location for a safety margin.

    The lower right box will display the actual boiling temp of water at your altitude.

    Copy these numbers to the upper boxes then put the desired temp (in Celsius) in the lower right box.

    The pressure that is displayed in the lower left box is the absolute pressure that is required for the correct temp. THIS IS NOT THE GAUGE PRESSURE!! You must subtract the number in the upper left box to get proper gauge pressure. See my example below.

    I live at 6800′ so i used the next higher elevation at 7000′ which is 11.3 psi. This is from the PDF shown above. This gives me a boiling point in an open container of 93C. With 11.3 psi and 93C in the top boxes, i put 116 in the lower right box for the desired temp of the canner. 116C=240F. The lower left box calculated that this temp occurs at 26 psi. Since i already have a pressure of 11.3 psi, i subtract this number from 26 and this shows 14.7 (15) psi for the gauge.
    Now that i know this, it can go in the front of my canning log for recall after the next EMP, CME, or crash my computer…

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