A Connoisseur's Guide to Fuelwood

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Hardwood, because it's denser, takes longer to dry than softwood. Wood from dead or dying trees contains less moisture to begin with so it seasons faster than wood cut from live trees. And any wood dries more slowly in cool weather and in humid climates.

You can speed up seasoning considerably by cutting the wood into shorter lengths and splitting it into smaller pieces. Stacking the wood in a wind tunnel or a solar dryer also speeds things up. A wind tunnel is any structure that generates a breeze or draft. We once had the perfect wood-drying place in the form of an open-ended shed on one side of our barn. The wind whistled through the shed and dried green wood in no time while the shed's roof kept off rain. A solar dryer speeds things up by concentrating the sun's warmth. Fashion one by covering stacked wood with a sheet of plastic propped away from the wood so that air can readily circulate and moisture will evaporate instead of condensing on the plastic and dripping back onto the wood.

Because it contains less moisture, seasoned firewood is lighter than green wood. As it dries, the wood takes on a weathered look and the ends tend to crack. When you strike two sticks of well-seasoned wood together, they "thwack" like a baseball bat hitting home. Strike two sticks of green wood and all you'll hear is a "thud." Compared to green wood (averaging about 4,000 BTUs per pound), wood that's been air dried to 25% moisture averages 6,400 BTUs. Properly seasoned wood ignites easily and burns at a higher temperature, so it burns cleanly.

Creosote

Burned in the presence of plenty of oxygen, dry wood produces only carbon dioxide, water, and a little ash — three materials that are readily recycled by growing plants. Green or highly resinous wood, by contrast, produces a mixture of wood tars and other wood extracts, collectively known as "creosote." These unburned, organic compounds are carried by smoke up the chimney and are deposited on the flue wall.

When hot, creosote is a viscous liquid. When it cools, it becomes sticky and tarlike. Eventually it dries into black flakes that peel off the chimney wall and fall down the flue. A serious creosote buildup blocks the flue's airflow, making the stove or fireplace hard to light and causing it to smoke when you finally do get it lit. Worse, creosote can be touched off by sparks, igniting a chimney fire.

A wood fire that burns hot and fast keeps the chimney too hot for creosote to stick. Instead, liquid creosote drips down the chimney and into the stove where it gets burned up. Because green wood can't burn hot, it's more likely to cause creosote buildup than seasoned wood is. And since softwood burns hotter than hardwood, softwood is less likely to cause a creosote problem than hardwood.

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