1. In a non reactive pan, whisk together sugar and salt. Stir in the water and lemon juice.
2. Turn the heat to medium high and stir in the blueberries, bring to a boil.
3. Once boiling, cook for 2 minutes stirring constantly, scraping the bottom to prevent burning.
4. Use an immersion blender or a food processor to puree the syrup for a smoother, thicker syrup.
5. Stir in the vanilla extract, if using.

Prepare the waterbath canner

1. Heat jars in simmering water until ready to use, do not boil.
2. Wash lids in warm soapy water and set aside with bands.
3. Ladle hot syrup into a hot jar leaving a ¼ inch headspace.
4. Remove air bubbles. Wipe jar rim. Center lid on jar and apply band, adjust to fingertip tight.
5. Place jar in simmering water canner. Repeat until all jars are filled.
6. Bring water to a boil and process jars 15 minutes, adjusting for altitude.
7. Remove jars and cool 12-24 hours.
8. Check lids for seal, they should not flex when center is pressed.
9. Label and sore in a cool dry place and use within 18 months.
10. Once syrup is opened, store in the refrigerator.