I just cut a 32"x3" tabletop from a walnut stump. How can I keep it from cracking during Air drying. ?
Maybe if you soak it for a day in Pentacryl. http://www.preservation-solutions.com/product/pentacryl/
You can't, they all crack. Maybe a little, maybe a lot!
That's basically true because wood shrinks roughly twice as much tangentially (following the rings) as it does radially (between pith and bark). Perfectly round pieces are the most likely to crack. I have posted these pictures before but they show that some cookies can be dried without major cracks.
(https://forestryforum.com/gallery/albums/userpics/10317/Cherry_cookies~0.JPG?easyrotate_cache=1483850394)
(https://forestryforum.com/gallery/albums/userpics/10317/heart~0.JPG?easyrotate_cache=1483850431)
Thanks Guys for the comments. I am going to wrap the edge in shrink wrap with the ends covered with cardboard and let it set about a year.
A fella once told me an inch per year minimum for air drying to give you the best chance for what ever that piece is capable of?
That "inch per year" thing has been spread around and around for years. Some species vary so much from other species that the saying becomes meaningless.
The 1" rule of thumb is a poor one. Plus a cookie will dry much faster than a board. Much faster.
Thanks, I never gave it much thought. That's my something new today.
In some places, the year per 1" to air dry might be right depending on when the wood was stacked, i.e. in late fall early winter with ice and snow for 6 months. Here in the South, My hardwood takes anywhere from 90 days (for maple and yellow poplar) to 120 days (walnut), to 180 days (pecan, red oak) to 240 days (white oak) to air dry to about 15%. This is for 4/4. Once the moisture content falls below about 20%, I put the wood in the kiln to dry it below 10%, so I monitor it pretty carefully.
We get good drying conditions year round in Middle Georgia as there is normally no ice and snow, and if there is any, it is a minimal amount and lasts only a day or two. Not the same in the frigid, cold, glaciated, Northern States north of the Mason Dixon line (AKA Yankee Country).
Putting a ratchet strap around the outside edge of a cookie will allow you to ad pressure while it dries. Every so often, tighten it up as it shrinks. This prevents major splits during drying process. It still may split after you take it off. My success has been good.
Quote from: fishpharmer on January 12, 2017, 11:20:56 AM
Putting a ratchet strap around the outside edge of a cookie will allow you to ad pressure while it dries. Every so often, tighten it up as it shrinks. This prevents major splits during drying process. It still may split after you take it off. My success has been good.
You've had good luck with walnut stumps this way?
Quote from: WDH on January 10, 2017, 08:08:27 AM
The 1" rule of thumb is a poor one. Plus a cookie will dry much faster than a board. Much faster.
Yes.
Cookies dry in a matter of weeks, or short months. Remember that the grain is oriented so it is all open. I did an experiment a few years back, and among other things, I had marginal success with applying clear sanding sealer to the top of a fresh cut cookie. The next day, I had found it would penetrate the wood and in some case would flow out the bottom before it cured. It seemed to fill the voids and kind of glue the cookie together. Sometimes....other times were complete failures.
Drying cookies is very problematic.
Low_48, no I have not used this on walnut. Only, cypress, oak and pine. It did not eliminate cracks, however it seems to minimize it compared to drying without the rachet strap.
WDH, yellowhammer and Den Socling have much more knowledge and experience drying than I do. Its just my opinion the rachet strap helps minimize splitting. There is no reason it would not help in drying walnut cookies.
Cracks, or one major crack, results because the tangential shrinkage in most species is twice the radial shrinkage. So the circumference is shrinking twice as much as the radius. Circumference = 2 x pi x r. So, we need to increase the radial shrinkage or decrease the circumference shrinkage. I do not see how a strap on the outside can do either of these two.
This differential is increased if we dry the outside before the interior, which can occur with a thicker cookie. Sapwood dries much faster than heartwood. Pieces without bark also dry faster from the edge. If we use a coating to slow drying, the key is to use it on the outside areas and not on the central section.
If we remove the core by drilling a large hole, it is now possible for the radius to decrease, and large cracking is prevented.
The circumferential shrinkage puts tremendous pressure in the radial direction. So, with very low density wood, the cells can collapse from this pressure in the radial direction, thereby preventing a major check.
Quote from: GeneWengert-WoodDoc on January 13, 2017, 08:49:07 AM
If we remove the core by drilling a large hole, it is now possible for the radius to decrease, and large cracking is prevented.
Doc,
If I were to use a 4" or larger hole saw and remove the center of a cookie (say a 24" pine or cedar, 2 or 3" thick), and then replace it (trimming if necessary) when dry - what are the odds of no cracking? I could coat the outer rings of the remaining cookie with sealer to slow them down.
This is about as much reasonable that you can do.