Backyard Maple Syrup

From the garden

• 10 gallons of fresh maple saps · the classic ratio is roughly 40:1; about 10 gallons of sap boils down to one quart of syrup

1. Boil outdoors: set a wide, shallow pan over a propane burner or a steady fire: 10 gallons of sap gives off gallons of steam that will peel paint and wallpaper in a kitchen. Start with a few inches of sap, keep it at a hard boil, and ladle in more as it reduces. Skim the foam as it rises.
2. Sap sours fast. Keep what you're not boiling cold and start within a day or two of collecting. When the whole batch is combined, reduced to a couple of inches, and turning golden, move it indoors to a smaller, deeper pot where you can control the finish.
3. Finish to exactly 7°F above the boiling point of water at your altitude: 219°F at sea level, lower as you climb, so boil a test pot of plain water first and add 7 to whatever your thermometer reads. Watch the pot constantly at the end; near-syrup foams up and boils over in seconds (a tiny dab of butter knocks the foam down).
4. While the syrup finishes, wash half-pint or pint jars and keep them hot in a simmering boiling-water canner; prepare the lids. Filter the hot syrup through a dampened wool or orlon syrup filter. Cheesecloth won't catch the gritty 'sugar sand' that clouds a jar.
5. Reheat the filtered syrup to 180–190°F, pour it into the hot jars leaving 1/4 inch of headspace, wipe the rims, and screw the lids on fingertip-tight.
6. Process in the boiling-water bath, jars covered by 1–2 inches, for 10 minutes. Altitude adjustment: 15 minutes at 1,001–6,000 feet, 20 minutes above 6,000 feet. Cool undisturbed 12–24 hours, check the seals, and refrigerate any jar that didn't seal.