Sawing Sweet Gum
Thoughts on how to cope with Sweet Gum's warping ways. January 8, 2010
Question
The first sweet gum I sawed was back in August and it turned out well. I’ve been sawing more from the same grove, 30-50 feet away, and you could build a silo with this stuff. There are cants rising up as much 3-4 inches in middle of bed. The only way I've been able to get any resemblance of straight boards is to quarter log and continually flip. I've read time of year shouldn't effect MC/stress but we've had a pretty wet spring. Any suggestions on an easier way, or maybe why these trees are sawing so differently?
Forum Responses
(Sawing and Drying Forum)
From contributor A:
That is not uncommon for sweet gum. Letting the logs lay for even a couple of months seems to let them relax somewhat. If they lay for very long they will spalt. Most of the time when sawing I take a cut or two then flip 180 and take a cut or two then flip again. Most of time I saw it 5/4 to get a 3/4 finished board.
From contributor V:
I sawed roughly 2,300 bf of gum about a month ago, and the stuff was very stable, without any major warping. One tree had issues with a rotten core and I believe it had a bacterial infection. The heartwood on this one tree, once cut past the rot had a heavily marbleized heartwood with odd lines looking something like zircote.
This white wood should not sit long in the summer heat if you wish to preserve the natural white sapwood color. Here in NJ most log ends of gum will average 1/3 heartwood and 2/3 sapwood, so if you have more heartwood and are specifically sawing for that, the heat in your area may not be such an issue because the heartwood takes longer to discolor.
I have not seen this wood spalt before and I imagine it will more likely discolor into ugly muddy forms, as this is not the time of year to start spalting for nice black lines. Proper sawing and centering the grain as contributor A stated should help.
From the original questioner:
Thanks for the tips. I was afraid to let them lay very long as in our area with the temp and humidity, it doesn't take gum long to deteriorate. We'll try to get the rest off the ground and give them some time. Thanks again.
From Gene Wengert, forum technical advisor:
The stresses in the tree with gum are well known to be very large from time to time. These stresses will be released when sawing, so it is best to turn the log frequently or to use a two saw cutting process, such as a Skrag mill or twin band, that cuts evenly off of both sides at the same time. Note that these stresses are more or less permanent, so log storage relaxes only a few of the stresses. (I agree that staining and spalting are a risk in warm weather.) These stresses will cause a great deal of warp in drying. 12" sticker spacing helps with top weights, but even then warp is common. Not all logs have these stresses, but the majority of sites do.
From contributor A:
For me this is the best time of year to get logs for spalting. I try to get all of my spalting stock in April and May if at all possible. For good sap gum boards I try to fell the logs in late fall and saw by February. They seem to dry out some and "relax" better. I try very hard not to saw heart gum in the heat of summer as checking is very bad.
