Cutting Boards Out of Case Hardened Wood

amistwood · May 10, 2019, 03:36:48 PM

I recently bought and installed a Woodmizer KD250 Dehumidification kiln and am learning the proper way to dry wood and at what rate to dry it at. The first load I ran was about 400 board feet of cherry wood and it came out case hardened. From what I understand about case hardened wood, the wood has more moisture on the inside of the wood than the outside. I have heard that you can try to fix it by steaming it however I do not have a steam system available to me.

Now that I have this wood and I don't have anything to do with it, I was wondering if it was feasible to make end grain cutting boards out of case hardened wood. My reasoning behind this is that when you cut the wood to make the end grain cutting board it is switching the outside of the wood to the inside and visa versa. Anyone have any thoughts on this idea?

Southside · May 10, 2019, 04:52:08 PM

You can also dump water onto the floor of your kiln, shut off the compressor, and crank the temperature to simulate the steaming effect and help to reduce the case hardening, it basically primes the pump and gets core moisture moving out. There has been additional advice offered that involves chickens and certain rituals but you probably don't need to go to that extreme yet. @YellowHammer @K-Guy any additional suggestions?

GeorgeFindlay · May 10, 2019, 06:06:26 PM

For my two cents:

Having made and donated/sold several (hundreds) of cutting boards, I wouldn't recommend using any case hardened wood in an end grain board. As you may know already, end grain boards are a lot of work relative to their long grain alternative. Any fissures will ultimately create an unstable offering, and potentially a bacteria laden environment.

If you do elect to proceed, I'd suggest you use a very good sealer such as 'The Wood Whisperer' recommends.

amistwood · May 10, 2019, 06:48:11 PM

thanks for the replies so far. I will definitely try the water on the floor with the compressor turned off. I was also thinking of putting a humidifier in the room throughout the drying processes in order to better regulate the humidity in the future if the problem arises again.

I did a little more research and found that you can plane down the wood to reduce stress. I ended up trying this technique on a few boards and then ran the case hardening tests again and it worked! The stress was relieved and I had perfectly straight forks on the few tests I ran on separate boards.

Is there any type of woodworking project that you could do with case hardened boards? I understand another large factor (other than board distortion) is safety with working with something that could pinch the blade as well.

YellowHammer · May 10, 2019, 11:05:35 PM

The effects of case hardening, or really having a moisture gradient from case to core can manifest itself in several ways, and can be dealt with in several ways. It not case hardening in the metallurgical sense but more of a dryer, shrunk and tight case overwrapping a moist and expanded core. So the trick is to remove the moisture gradient, either by equalizing the case to core moisture levels, or physically removing the case material. I've done both and equalization is a better long term solution, as it results in more stable wood.

If running the wood through a planer, it's vitally important to balance the stresses and balance the wood. Basically remove all the moisture gradient wood down to the neutral axis of the board, (think removing the outsides of an Oreo cookie). It's possble to plane off of one side, make the board bow in one direction, and plane off the other side, and make it bow the opposite direction or even straighten. Very hit and miss, but I've done it. However, if there is still a moisture gradient, as the wood continues to dry, those fibers will shrink and the board will start to move again. So usually planing is only a temporary fix.

A more permanent solution is to let the wood sit, and give it time to equalize the case to core moisture levels. Just put the wood in an out of the way place, and forget about it for awhile.

Raising the temp in the kiln can sometimes do moisture gradient corrections, without the compressor running, and you will see the boards start to "sweat" an indication that the core is losing moisture and he case is gaining it.

If the wood movement is caused not by uneven moisture levels but internal physical stresses in the fibers of the wood, then it's a whole different ball game. Very difficult to un stress wood, but it can be done to some degree with high temps and pressures. Basically steam straightening instead of steam bending. However, I've found that it takes at least 150F to 160F to even get close to the threshold heat required.

Of course, some of these techniques border on Voodoo and are unpredictable at best, although I have had success with them. Chickens sometimes help.

low_48 · May 12, 2019, 12:13:06 AM

The project would depend on how wet the core of the wood is. My concern would be checking with anything you made. You might consider primitive furniture since there is a whole group of folks making items from pallet lumber. Even covering home walls and bar fronts with junk wood.

K-Guy · May 13, 2019, 08:32:57 AM

@amistwood @YellowHammer

Hi Stan from Nyle here.
Usually case hardening can be fixed or lessened by pouring 5-10 gallons of water on the floor of your kiln, then raising the temperature to 140° F and leaving it for at least 24 hours upon reaching that temperature. If you have any more questions you can reach Nyle service at 800-777-6953 and push 6.

Yellowhammer, again with the chickens?!?!