Preventing checking and drying cracks; suggestions welcome

[Denis Houyoux]

At the school where I work, there are a lot of old trees. Mostly oaks, but some other nicer varieties as well. I have done my best to have the grounds people let me know when one comes down or they have to take one down, so as to hopefully be able to aquire some of the lumber. Just this week the head of the grounds department came to me and told me that they were looking at possibly taking down one of the large oak trees on the property, due to it's failling root system. We're talking about a white oak, approximately 4 to 5 feet in diameter, and from the estimates I've heard, over 200 years old. What I would like to do is to be able to save a slice from near the bottom of the trunk and eventually sand and finish it smooth, and use this slab as a timeline. Basically put little markers on the different rings showing things like when the revolutionary war took place, or the civil war, or the founding of the school, etc....
Can anyone out there help me out with suggestions on how to make this possible? My main concern is being able to salvage a slice and keep it from cracking or splitting. I have never done this sort of thing before, so I have all kinds of questions. Please feel free to contact me either by replying to this post or by email: denis_houyoux@woodberry.org

Thank you,

Denis Houyoux

[Dick Strauss]

Denis,
You want the piece to dry extremely slowly. Possibly you could use anchorseal or apply finish almost immediately (before the slab dries much) to slow the drying rate.

I don't think you'll be able to keep something that large from cracking. I'd suggest you cut the slab and maybe make two cuts from the bark to the pith to relieve the stresses of drying. That way you can help control where the cracks occur. Then you can still create the display you want.

[Jim Becker]

Slabs/sections like you want are extremely difficult to preserve without cracking no matter what you apply to them. You may be able to put a metal band around the slice and then coat the faces with Anchorseal or melted paraffin and get success, but without the constriction of the band, the slice almost "must" crack as it dries.

[Jeff Raymond]

Drying wood properly is both an art and a science. It also depends on a host of other factors, such as ambient humidity, temperature, species and thickness of wood, etc.

One of the secrets to a kiln is that the operators carefully control every step of the drying process.

Air drying lumber is kind of a hit and miss situation. Plan on a fair amount of waste. In New England, a properly 'sticked'; pile, protected from the rain/snow dries about an inch a year. So, 8/4, for example, would take about two years.

It's also a big undertaking to avoid rot and mildew, etc. If you have the time and energy, go for it; you may be able to get some useable lumber, and know that you were able to go from tree to finished product yourself. It's a cool thing to do if you pull it off!

[Howard Acheson]

Use this stuff: http://www.rockler.com/product.cfm?page=686

It's made for what you want to do.

[Richard M. Wolfe]

A slab that large, expecially a cross section, is probably going to crack. What may help, assuming that only one face is going to be seen, is to go into the "bottom" and make a series of relief cuts to alleviate drying tensions in the wood. Some sawyers, when cutting a solid wood mantle that may be several inches thick, will make chainsaw cuts into the back. This relieves tension and also allows the mantle to dry because some thick slabs may never dry on the very inside depending on wood species.