“Can I use the oven for plastic lids?” No. Plastic melts or deforms above 200°F. Stick to metal lids, or sterilize plastic separately with boiling water.
“What if my jars are vintage or thin?” Lower the temp to 250°F and increase time to 30 minutes. Thin glass can crack even at 275°F if it’s old or has hairline fractures you can’t see.
“Do I need to boil the jars first?” Not if you’re using the oven. But if you’re paranoid (I get it, Clara was), you can do a quick 10-minute hot water bath, then transfer to the oven for drying. Just be gentle.
Look, I’ve ruined more batches than I want to admit. One time I forgot the jars in the oven overnight and they came out like brittle archaeology artifacts. Another time I pulled them out too fast and heard a tiny ping—that was the bottom of a jar separating.
The perfect oven sterilization is 275°F for 20 minutes, cool down slowly, and always check your gear. Your jam will thank you. Your future self—the one eating peach preserves in January—will high-five you.
Now go forth and sterilize. Your jars are waiting.