How to measure and regulate the moisture level of wood?
The ideal level of moisture content in wood meant for woodworking depends on two factors – your geographic location and whether the final product will be stored inside your home or outside. In general, however, acceptable levels of moisture content range from 6-12%.
In order to find the right moisture content for your wood, you will need to take into consideration the humidity of the location where your finished product will be used. To understand why you first have to consider how moisture will affect your wood.
When humidity levels drop and the wood moisture content decreases, the wood also shrinks. Varying humidity levels in the environment and moisture in the wood will determine how the wood expands or shrinks. It is important that you know and understands what moisture levels are acceptable so that you don’t wind up with a messed-up carving—the recommended levels of moisture range between 6 and 12%.
Oven dry testing
As the wood is being dried, the weight is checked in set intervals of time. Once the sample’s weight stops changing, the weight is compared to what it was before the start of the drying. The difference in weight is then used to calculate the original moisture content.
There are several drawbacks to this type of testing. It is a time-consuming process – properly done, it can take hours. If rushed, the wood can often burn.
Aside from this, the wood sample that was used for the drying process is often rendered unusable for woodworkers – the exposure to heat and the drying itself can lead the wood to warp and deform. Furthermore, oven-dry testing requires specialized equipment that not everyone has access to, especially if you’re not a professional woodworker.
To use the pin-type of meters, here’s what you will need to do:
- Stick the pins of the meter into the wood.
- Align the pins with the grain of the wood.
- Turn the meter on. At this point, the electrical current will course through the wood, resisting wood better than it does water.
- Take the reading.
Or you can use the pinless meter.
- Place the scanning face of the meter against the wood. Try to choose a large flat surface of the wood.
- Turn the scanner on
- Run it along with the wood.
- Take the reading
Whether you are using a pin-type or pinless, scanning the wood or taking the reading shouldn’t take more than a few seconds.
This boils down to dry wood producing less resistance. The pinless meter doesn’t have electrodes to be inserted into the wood. However, they use an electromagnetic sensor to detect the amount of water that is in the wood. The work is similar way that a scanner works for documents. All you need to do is run the meter over the wood. Just make sure that you run it over a large surface of the wood. These meters are often more accurate.
The great thing about pinless meters is that they do not leave holes in the wood. As such, it is always better to use pinless meters on wood that you would not want to get any holes in, such as expensive artifacts. Here are some expected figures that you could work with.
If the in-use location’s humidity is between 19 and 25%, and the EMC is at 5%, then the corresponding EMC needs to be at 5%. If the humidity is between 47 and 52%, the EMC at 9%, then the MC (moisture content) will also be 9%.
How to lower moisture content in wood
The rule of thumb for this method is to allow for a year of drying time per inch of thickness of the wood. However, this can be sped up to between a few weeks and a couple of months by air-drying indoors and using a heating system, dehumidifier, or fan to quicken the process.
There are various types of kilns that you can use to dry your wood, but all operate under the same basic premise – a large, insulated chamber is used to introduce heat to the lumber. Kiln drying allows you to control the temperature and humidity levels.
This can be a very effective process when it comes to drying wood quickly, but you will need to be careful. It can be easy to over-dry the wood, to a point of destroying it completely.
The best way to go about it is to microwave it for short periods and test the moisture content between each round of drying. Using a moisture meter is recommended.
In order to check on the moisture content of wood, you can use a moisture meter. If the wood moisture content is above normal, you will find that your carving may not hold up for long, hence why the MC levels are something that you will need to be on the lookout for.
If there is too much moisture in the wood, then the wood may shrink.
If there isn’t enough moisture in the wood, then the wood will expand and this may cause it to buckle or bow, which will harm the carving you are working on.
Be careful also, not fall for common myths surrounding the wood. Some myths claim that wood will expand when it is hot and contract or shrink when it is cold.
This is a myth because the moisture in the wood cannot freeze. After all, the chemicals are stuck to the walls of the wood. The outside temperature will not affect the wood or cause it to shrink or expand.
Before you use wood, you must allow it to acclimate first. Once this is done, its moisture content will be in tandem with the room humidity level, also known as RH.
The eventual EMC will be a value derived when the wood’s moisture is balanced with the environment’s moisture. You want the wood to find its stable state with its environment. Most furniture and wood carving does well with wood moisture content that is at 9%. But this is before you factor in the moisture content in the environment.
If your wood has more moisture than you need it to have, you will need to dry it to reach the right levels. This is to prevent your work from sharing, cracking, or warping.