If you are canning jelly - and using melted paraffin to seal the hot in boiled jars why do notice a trail of bubbles coming through 15 hours later?

The trail of bubbles that you observed in the sealed jelly jars is likely caused by the presence of air pockets or trapped air within the jars. These air pockets can be introduced during the canning process, especially if the jars were not properly filled with jelly, leaving headspace at the top. As the jelly cools, the air pockets may rise to the surface, causing the paraffin seal to bubble.

Here are a few reasons why air pockets may occur during the canning process:

1. Incomplete filling of jars: If the jars are not filled with jelly all the way to the rim, leaving a significant amount of headspace, air pockets may be trapped inside. To avoid this, make sure to fill the jars as close to the rim as possible, leaving only a small amount of headspace (usually 1/4 inch or less).

2. Bubbles in the jelly: If the jelly was not stirred thoroughly before pouring it into the jars, bubbles may have formed within the jelly itself. These bubbles can rise to the surface during the canning process, leading to air pockets under the paraffin seal. To prevent this, make sure to stir the jelly well before filling the jars.

3. Inadequate sealing: The paraffin seal must be applied hot and thick enough to create an airtight barrier. If the paraffin is not applied properly or if it is too thin, air may seep through, causing bubbles to form. To ensure a good seal, pour the hot paraffin onto the jelly surface, making sure to cover the entire surface and the edges of the jars. The paraffin should be at least 1/8 inch thick.

It's important to note that the presence of air pockets in canned jelly does not necessarily indicate that the jelly is unsafe. However, it may affect the quality of the jelly, such as its color and texture. To avoid the formation of air pockets and ensure proper sealing, follow the recommended canning instructions carefully and pay attention to details such as proper filling, stirring, and sealing.