Surprisingly, many woodworkers do not have moisture meters, and of those who do own them, most seldom use them. With wood being as active as it is, it seems that using a moisture meter to help determine the amount of wood movement would be pretty important. To novice woodworkers, wood movement is something that is not well understood, but it is a very important component of woodworking and needs to be studied by any serious woodworker. As we all know, wood, even after it is cut is constantly either absorbing moisture or giving off moisture. This is the a nature of wood. The absorption of moisture is primarily taken in through the end grain of wood, but some moisture is absorbed through the side side grain as well.
The result of this moisture absorption is that the cells of the wood expand, and can, in some situations, damage woodworking projects by breaking glue joints, expanding doors, having some wood material bow, and generally making your hard created woodworking project distorted at the least and even destroyed in rare conditions.
But as everyone knows who is working with wood, movement needs to be understood in order without the wood coming apart on you or reacting in some way you don't know. Knowing how moisture meters work can help you understand how to use them properly ....
There are 2 basic kinds of moisture meters, pin type and surface type, and both of these are equally accurate assuming all conditions are equal. Every moisture meter is simply a highly accurate multi meter that has been adjusted for finer readings. A pin type meter for example is calibrated to measure a certain amount of electricty that will pass between both of the probes or pins. It's really just that simple.
Many people ask me which type of meter they should purchase and I have a simple answer. If you are a home builder, home renovator or other trades person that may be dealing with moisture in buildings, particulaly in peoples homes, you will undoubtedly want to purchase a surface meter. Incidently there are some moisture meters that will do both surface and pin readings using the same meter.
This is an image of a simple analoge, pin type moisture meter
The reason you would want a surface meter is because you want to get readings in many different locations without having to puncture someone's sheet rock or inside walls. Also, a surface reading meter can give you reading deeper inside a wall structure that a pin type may miss.
Those people who would benefit more from a pin type meter are flooring installers who are need to make accurate readings of wooden flooring before install, where they are often reading multiple places on multiple boards. Woodworkers may also benefit from pin type meters, again because readings of boards that are stacked in piles are best done with pin type because it isolates the readings.
Other issues that can affect the readings are ... surface readers need clean flat surfaces, pin types can take readings in rough, uneven wood like wood turners or carvers may often be looking at, or anyone who is purchasing rough woods.
The next question is what is the moisture reading I should be working with? and that answer is also difficult to give a generalization answer to because it depends what you are making, where you live, and where the wood project you are making is going to be residing. For example, a friend of mine who does woodworking in Santa Fe, New Mexico tells me he likes to have his moisture content down around 3 percent, especially if his client is going to be living in the desert area.
I live in the Pacific Northwest area where moisture contents are quite acceptable once they are around the 9 - 10 percent area, but if I were going to send a wood piece to New Mexico with that moisture content, it is likely some gaps could open up, depending on the piece, so it really does make a difference. Then there are the folks who live with high moisture contents in the summer when it is hot, and very dry and cold in the winter. With such variables, I can only assume that picking a medium moisture content number like around 9 percent is about all that they can do ... but, we would love to hear from any readers in the comments section of this article as to what they do.
Moisture content is a very important element of woodworking and the knowledge of how wood moves as it aborbs and releases moisture will determine how you work with the woods you use. If you don`t have a moisture meter, you may want to consider, even one of the lower priced ones to at least give yourself a starting point in what level of moisture your wood is at. If you are purchasing rough lumber and air drying it, a moisture meter is a must.
Copyright - Colin Knecht