You don't need a microwave - but you do need to heat jam to get it to set. Setting levels depend on pectin, but you can check by spooning some on a cold plate. A saucepan or jam pan is the more traditional way that I use (allows big batches too)
Jarring in a heated jar and sealin when warm prevents bacterial action
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Jarring in a heated jar and sealin when warm prevents bacterial action
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