End Checking and Sticker Placement

      Placing stickers very close to the ends of the lumber stack can help limit end checking. This thread also offers additional tips on preventing checking. November 16, 2010

Question
Over the years I have seen that in the air drying yard, the end checks or splits stop at the first stick. We do end wax our green lumber before air drying. Is there any benefit to moving the outside sticks out as close as possible to the ends of the pile?

Forum Responses
(Sawing and Drying Forum)
From contributor D:
That's how I do it - very little end checking.



From the original questioner:
Thanks. But let's say that we have a trimmer and we set it up to trim everything at 2" over length. Should I then, on the end with the over-length, move my stick pocket out to help prevent the checking?


From contributor T:
Stickers as close to the end as possible seems like a win-win. Even if you trim off 2" of the end that does not have checks, you are not losing anything that you would not have lost otherwise.


From contributor A:
Keeping the sticks out to the end is fine, but if you are end sealing and they are still checking badly, I would look at my sealer. Another thing to look at is wind and sun location on the stack. Most of our hardwood logs are 6 inches longer than the whole foot, so a lot of checking is cut off in trimming. A sun blocking cloth on the ends may help more than sealing the ends and sticker placement.


From Professor Gene Wengert, forum technical advisor:
With proper end coating, end checking will be 99% eliminated. Moving sticks to the end will prevent a lot of checking from going more than 1". With check prone species, some will go further; with lower density, non-check-prone species, stickers at the end will be very effective. Of course, on an 8' board, each 1" of trim is 1% loss. So, end coating is better for oak and other check prone species. One problem with sticks at the end is that they will fall out if the pack is lifted with a forklift and transported, especially on a bumpy road. Also, with end coating, it is possible to shorten the logs. If each log is 4" shorter, this means that the next log up the tree will be slightly larger in diameter and that can add to the yield.


From contributor S:
Gene, I have coated all my logs when they were felled, but still see checking at the ends. Does it help to additionally end coat the boards after they have been cut? Should I coat the top and bottom of the board for a couple of inches beyond the cut (on the face)?


From Professor Gene Wengert, forum technical advisor:
We did a study coating the ends of logs in the summertime and found very few checks, if any. Perhaps the coating is not thick enough or there is ice on the ends so you are coating the ice and not the wood. You should have really good results.

We do know that once the wood checks, coating is not very effective. So, with that in mind, recoating would be a good idea, if the wood has not checked. I suggest that you avoid coating the faces. If the faces are coated, we seem to see some internal checks at times. I suspect that face coating discourages drying, so the ends remain too wet.

Some people will be unable to move the stickers to the ends, as their lumber has variable length. It is suggested to, when stacking, put all the lumber even at one end, end coat this end well and/or move the stickers to the end. The ragged end (unless the lumber was double end trimmed (DET), will require end coating, as it is more important to have the stickers vertically aligned than at the end. If you are going to end coat one end, then why not coat both ends?



From contributor T:
Where are walnut and oak on the list of prone to end checking? Did you ever develop a chart?


From Professor Gene Wengert, forum technical advisor:
Both are quite prone to end checking. I do have a listing in Drying Hardwood Lumber - each species is listed with the riskiest defect during drying.

Incidentally, we would not use end coating for lumber on sticks that is only to be air dried or dried under 130 F, as we will see an accumulation of wax on the stickers and they will get slippery. We might also be concerned about wax getting on various pieces of equipment in these cases. If kiln drying at over 130 F, the wax evaporates and so there is no carry-over.



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