Place sugar and water in a large stock pot. Simmer sugar and water mixture until sugar dissolves. Turn off heat.

Gently remove the lilac flowers from the stems and rinse in a colander like this one to remove any dirt and insects. Place the rinsed lilac flowers in the stock pot. Stir. Bring the mixture to a simmer over low heat, and let it steep for about 20 minutes.

Pour the mixture through a fine mesh sieve or strainer to remove the flowers from the liquid. Heat liquid up again, until just simmering. Pour the liquid into sterilized pint sized canning jars, leaving 1/2 inch head space. You can easily measure the head space with this inexpensive canning funnel.

Wipe rims of jars with a damp paper towel or dish towel and place sterilized lids and rings on jars.

Place jars in a boiling water canner and make sure you have 1 inch of water above the tops of the jars. Add additional water if necessary. Bring water to a boil and boil for 10 minutes.

Remove jars from canner and place jars on a towel on the kitchen counter to cool. Lids will make a pinging noise when they seal. If in a couple of hours the lid isn't flat and sealed, then place the jar(s) in the refrigerator to use in the next couple of weeks. Sealed jars can be stored in a cool dark place for 1-2 years.