REASONS WHY JUICES ARE DRAWN FROM JARS WHEN CANNING WITH STEAM PRESSURE
1. Open pet cock after pointer or gauge has reached zero; test for pressure by opening pet cock slowly at first. The gauge does not register pressure until about one pound of pressure has formed, hence opening the pet cock before the pointer is at zero means that from one to two pounds of pressure is being relieved and this will draw the juices the same as allowing the boiler to stand and a vacuum to form.
2. Allowing the pressure to fluctuate during the time of sterilizing, such as running the pressure up to fifteen, back to seven or eight and then up again.
3. Wire bails can be and should be a little tighter when jars are put in a steam pressure canner. The clamp should be left up as stated.
4. There may be an escape of steam around the seal of the boiler and this would allow the pressure on the inside of the boiler to fluctuate.
Any one of those four things will always cause loss of juice.
OPERATION OF HOT-WATER-BATH OUTFIT
These four rules will help in the operation of the hot-water-bath canning outfit: Example, wash boiler.
1. Support the jars off the bottom sufficiently to permit the circulation of water under and around the jars.
2. Have the water cover the tops of the jars by at least one inch. The heat and pressure must be equal on all parts of the jars.