I generally preboil the wort for a few minutes to get a good hot break prior to canning. This allows me to keep a majority of the hot break out of the jars. When you fill the jars, the wort should be hot anyway. You get more even heating of the jars and contents as you approach processing temperatures. I still get a little hot/cold break in the jars, but I pour most of that into the flask with the wort. The hot break provides a few nutrients the yeast needs.
I leave about 1/2" head space in the jars. Make sure you
do not tighten down the rings prior to processing. Screw them on enough to keep them from falling off. This allows for steam to escape from the jars. As the jars cool at the end of processing, the contraction of air will suck the lids down tight and create the seal. As you take them out of the pressure canner, you tighten the rings down. Once the jar contents are completely cool you can take the rings off as they will no longer be needed once the rubber/plastic ring molded into the lid solidifies. I leave them on so I don't lose them before the next canning session.
Losing liquid out of the jars during process is due to one of three things. The first is overfilling. Don't fill them to the brim thinking you will allow for boilover losses. This can actually result in jars not sealing as you need a clean surface for the lid to seal.
A second loss can be do to too high heat during processing. Keep an eye on the pressure guage (if you have one) to make sure the pressure doesn't get over 16-17 psi. If you just have one of those weight thingies, turn the heat down to where it still releases steam and doesn't bounce around like it's going to fly off into space.
The most common reason for loss is rapid release of pressure at the end of processing. As the pressure increases the temperature at which liquid boils goes up and vice versa. At pressure you can have liquid at 230° that isn't boiling. If you quickly drop the pressure, the liquid in the jars will still be at a temperature above the boiling point and will begin boiling violently. Think about the boilovers you get when you are bringing wort to a boil in your brew kettle and forget to turn the heat down. The same thing is happening in the jars. You need to take the cooker off the heat and let it sit for an hour or so until the pressure drops on it's own. Resist the temptation to let a little pressure out from time to time. This is the biggest problem I have when I am canning 5 gallon batches of wort. I have to do 3 rounds of canning. Waiting for the cooling between rounds takes a lot of time and make for a really long day of canning.
I've been canning (or at least helping) for over 50 years now, starting as a kid helping my mother with our huge garden. I also went through extensive training in food preservation with trainers from the Ball Corporation when I got my certification to operate a community food preservation center out in Colorado many years ago. I've seen just about every thing that can possibly go wrong with canning stuff (including exploding pressure cookers
). Pressure canning is great stuff, but you need to show great respect for it. Steam at those pressures and temperatures can cause quite a bit of damage to the human body. Always be careful.
Wayne
Bugeater Brewing Company
