Today is my first attempt at canning anything. Someone gave my husband a sack full of pears, so I thought I'd try pear preserves. I only had enough for about 1 full jar and just over 1/2 jar. Can I process a jar that isn't full in a boiling water canner? Everything I read says to leave 1/4 inch head space, but nothing about having any more space than that. Thanks in advance for the advice!