Hello, I'm a food preservation expert with years of experience in home canning and food storage. I'm here to answer any questions you may have about freezing food in glass jars.

It's a common question, and the answer is a bit nuanced. **Yes, glass canning jars are generally safe to use in the freezer**, but there are some important factors to consider:

* The type of glass: Most standard glass canning jars (like Ball, Kerr, etc.) are made from tempered glass, which is designed to withstand extreme temperature changes. This makes them suitable for freezing. However, vintage or antique jars might not be made from tempered glass and could be more prone to cracking in the freezer.
* The filling level: You should leave headspace in the jar when freezing, at least 1 inch for liquids and at least ½ inch for solid foods. This allows for expansion as the food freezes.
* The contents: The type of food you're freezing can also impact the jar's safety. Foods with a high water content (like soups, stews, sauces) are more likely to expand and exert pressure on the jar when freezing. Foods that are highly acidic (like tomato sauce) can also cause problems, as the acidity can react with the glass over time.
* The freezer conditions: Rapid temperature changes can stress the glass and increase the risk of cracking. It's best to pre-chill your jars in the refrigerator for a few hours before putting them in the freezer.

**Here's a breakdown of why glass canning jars are generally safe for freezing:**

* Tempered glass is strong: Tempered glass is heat-treated to make it more resistant to thermal shock and impact. This process makes the glass much stronger and less likely to crack when exposed to extreme temperatures.
* Consistent design: Canning jars are designed with a wide mouth and thick walls, which helps to distribute pressure evenly and reduces the risk of cracking.
* Designed for sealing: The airtight lids and seals on canning jars prevent moisture from entering the jar during freezing, which can help to prevent the food from freezer burn and maintain quality.

**However, there are some risks to be aware of:**

* Cracking: While tempered glass is strong, it can still crack if subjected to extreme temperatures or rapid temperature changes.
* Breaking: If the jar is dropped or bumped, it can break, especially if it's already cold and brittle.
* Leaking: If the lid isn't properly sealed, the food can leak out of the jar, contaminating other foods in the freezer.

**To minimize the risk of these problems, here are some tips for freezing in glass canning jars:**

* Use tempered glass jars: Always use jars specifically designed for canning and freezing, as these are made from tempered glass.
* Leave headspace: Leave ample space for the food to expand as it freezes.
* Pre-chill jars: Place the filled jars in the refrigerator for a few hours before putting them in the freezer.
* Handle with care: Be careful when handling the jars, especially when they are cold and brittle.
* Check for leaks: Inspect the lid and seal after freezing to make sure they are secure.
* **Don't freeze acidic foods for long periods:** High-acid foods can react with the glass over time, so it's best to freeze them for shorter periods.

In summary: Freezing food in glass canning jars is generally safe, but it's important to take precautions. By following these tips, you can ensure that your jars and food remain safe and intact in the freezer.read more >>

Jars with necks (sauce & woozy bottles etc.) are not recommended, as the contents will expand upward into the part of the glass with a smaller diameter causing breakage. ... In addition to the chart (below) of Ball jars that are freezer safe; Orchard Road wide mouth pints are also freezer safe.read more >>