Set six canning bands (some call them rings) aside, near where you will be filling the jars.
Place the six glass jars in the water bath canner. The water should cover the jars by at least an inch. Turn the heat to medium high.
Place six jar lids in the small saucepan with enough water to cover the lids. Cover the pan and heat the water on low.
Rinse and drain the raspberries.
While raspberries are draining, measure out the sugar into a bowl so it's ready to add to the raspberry mixture all at once later on.
If you are using fresh lemon juice, cut a lemon in half and squeeze out juice.
Juice the lemon with a small strainer (if you have one) placed over a measuring cup.
Pour raspberries into a large skillet. Add the lemon juice and water, if using. Bring the mixture to a boil over medium high heat.
Reduce heat and simmer for about 10 minutes.
Mash the berries with a potato masher or blend with an immersion blender.
To separate the seeds from the liquid mixture with no mess, place your fine mesh strainer over a medium saucepan. Pour the hot mixture into the strainer.
Press the seeds with a spatula or wooden spoon and move them around to make sure the holes in the mesh are not blocked. The liquid will drain into the saucepan.
When the dripping has stopped, set the mushy seed mixture aside.
Add the juice back to the skillet and add the pectin. Bring the mixture to a full boil while stirring constantly.
Add the pre-measured sugar all at once. Bring to a full boil and boil for 1 minute while stirring.
Using tongs, if you have them, lift hot jars out of hot water.
Ladle hot syrup into jars, leaving 1/4 inch headspace.
Once all jars are filled, wipe jar rims. Place lids on jars and place bands on jars. Adjust until they are fingertip tight.
Place jars (using a jar-lifter, if you have one) in the hot water bath in the canner. Water should cover the jars by at least one inch.
Bring the water to a boil and process the jars for 15 minutes, adjusting for altitude.
When processing is done, remove the jars (again using a jar-lifter, if you have one) and place them on a towel to absorb the drips and to cool.
If all has gone as it should, you should hear the jars seal as they cool. When they are cool, usually after about 8-12 hours, press the center of each lid. They should not flex.
Label and store the jars in a cool, dry place. The quality is best if used within 18 months. Refrigerate any jars once opened.