All is not what it seems when it comes to measuring the moisture content in firewood. A live tree such as birch hardwood that is cut fresh off the stump, (aka ‘green’) then split and stacked, should have a very high moisture content.
A new client asked us for a specific size, 12 inches long with a 3 inch face. For their purposes, it’s the ideal size for their senior parent to manage. On this day Gina is splitting a 12 inch diameter block of birch hardwood. As the splitter knife presses into the cut face of the block you could see moisture being squeezed out. As it should. After all, this tree was harvested only 3 weeks earlier.
Next we test the moisture content of the split pieces using a economically priced hand held moisture meter. Now, the first thing people should know about reading moisture content of wood is that the colder the wood is, the less accurate the moisture content reading will be. As this picture shows below, it is impossible that this piece of birch is only 23.8% moisture content. It should be in the 50-60% range.
The only way to get an accurate reading is to bring the up the core temperature of the wood. Once we loaded the kiln, we insert the sample probes for reading moisture content. While I don’t have a picture to show at that time, the moisture readings were near the same as the hand held unit, averaging 25%.
After a day with the heat on, the core temperature starts to rise in the hardwood and we begin to see a more accurate reading of the moisture content. In the photo below you can see that the average is 58%.
That’s a high moisture content to go into the kiln. A couple of issues that have to be closely monitored is to make sure the level of humidity in the kiln does not get to be too high for too long a duration, otherwise mold will start to grow on the wood surfaces. You can control this by either reducing the heat or you can exhaust some of the heat air (along with some of the humidity). Either method increases your cost for the drying cycle. Ideally you want the wood going in the kiln to be 35% moisture content or less. This will allow for a more manageable approach to the drying cycle, less chance of mold occurring, and a shortened cycle of drying time.
This load took 12 days. Probably the longest cycle to date we’ve had to manage. But now it’s ready to load in the truck and out for delivery.
If you require firewood supply for your home or business and are looking for dry firewood, reach out to us. We love splitting firewood and will be happy to help you with your heating needs.