It’s time for the canner to come out of winter storage.

As you dust it off, you may remember some jars from last year that didn't turn out exactly as planned. Why do your tomatoes float in the jar? You may have used overripe tomatoes, packed them in the jar too loosely or processed them too long or at too high of a temperature.

Here are some reasons why your food may not have come out as expected and some tips for ensuring perfection this summer.

One of the most common complaints from home canners is that the jars lose liquid during processing. There are several reasons this can happen:

• Food was packed too tightly. Food shouldn't be packed so tightly that it doesn't move around in the jar.
• The jar was filled too full. Be sure to always leave the headspace recommended for the food you are processing.
• Fluctuation of pressure or pressure that is too high.
• Forcing the pressure down on the canner by pouring cool water over it causes a sudden drop of pressure, which can siphon liquid out of the jars.
• Opening the petcock before the dial gauge returns to zero can also cause a sudden loss of pressure.

There are a variety of reasons jars don’t seal:

• Screw bands that are rusty or dented.
• The screw bands are on too tight or too loose.
• Small particles of food that have attached to the rim of the jar when it is being filled or when the liquid in the jar boils over during processing. Always wipe the rim of the jar with a damp clean cloth before putting the flat on the jar.
• Re-using flats — be sure to use a new flat each time.
• Boiling the flat — the rubber on the flats is softer than it used to be, so most need to be heated but not boiled. Follow manufacturer’s instructions for the flats.