Fill a large, heavy-bottomed saucepan with ice water and set aside.
Spray lollipop molds with cooking spray or, if you aren't using molds, line a baking sheet with parchment paper.
In a medium-sized, heavy-bottomed saucepan on medium-high heat, combine grenadine, sugar, corn syrup, and lemon extract.
Stir regularly and bring to a boil.
Continue to boil until the mixture reaches 300 F on a candy thermometer. Watch VERY closely. If it gets much higher than that, it will burn. I highly recommend that you use a digital candy thermometer with an alarm. That way, turning your back for a minute won't cause you to burn your candy. If you don't have one, just don't turn your back!
Immediately move the hot pot into the ice water bath and leave it there for just 20 seconds.
Pick the pot up and swirl it around for a couple of minutes to let it continue to cool and thicken a bit.
For lollipop molds: Working quickly, spoon mixture into lollipop molds. Put the lollipop stick about halfway up the candy (as shown below) and swirl the stick around so that it is completely coated with candy. For baking sheet method: Drop spoonfulls of the candy onto the baking sheet. The beauty of this method is that you can make your lollipops as big as you want! Put the lollipop stick about halfway up the candy (as shown below) and swirl the stick around so that it is completely coated with candy.
After the lollipops cool, remove them and they'll be ready to suck!