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Spring is here, and we may finally be able to put the wet weather behind us and tackle the many challenges that are a direct result of the winter weather. As a former logger and sawmill owner, I have lived through weather pitfalls. Let’s discuss.
As a logger, once the rain starts falling, you are restricted in many ways by nature and as a result, you adjust your process. One adjustment I always made was to never stop cutting trees. Instead, I simply stockpiled them in the woods and waited for a clear, dry day to haul them to the mill. This was the only way I could exist in the logging industry, but it does have its negative side effects – number one being STAIN.
After a very wet season, sawmills will notice a lot of logs that seem to be much older and show signs of degrading. This condition is directly related to the length of time since being cut and then the time spent stockpiled. It is critical to implement the practice of “first in – first out” inventory strategy, immediately after a long, wet season.
I have heard it said, on more than one occasion, that the lumber was “dead-piled” for too long and thus the reason for stain in the sapwood. The fact is, wood begins to dry immediately upon the first cut, so it should be processed immediately, and the drying process controlled to minimize the negative effects to the wood.
This brings me to my point for this month’s article, stain and its effect on grading. As we begin to cut lumber from the logs that were in a very bad environment for drying (piled at the landing), we start to see streaks and discoloration from the ends of the log and sometimes in areas where the bark was scraped off. This is considered stain, whether enzymatic or fungal and will cause degrade in the lumber.
I have witnessed several strategies over the years to try and combat staining and they all involve inventory management. Although cutting the oldest logs first may not coincide with your need to fill orders on quick turnaround species such as poplar or soft maple, it is the best method of combating stain.
Ultimately, I suggest shorter and smaller log piles at the mill and sorting by grade and age. This strategy will give sufficient runtimes at the mill to lessen the impact of species change-overs while maintaining a “first in – first out” inventory.
Dip chemicals are a very good tool to utilize when the time period from sawing to stacking or yarding, is an issue, it is not the solution for log stain. Log stain cannot be reversed once it has begun. Bottom line . . . saw the logs before they have an opportunity to stain, start the “controlled” drying process on the lumber as soon as possible and dip when needed to control the stain.
As always, I stand at the ready to answer your lumber grading questions. Contact me at [email protected] or at 901-399-7551 or send me your questions on Facebook during Live with the Chief.
Most industries have moved towards optimization technology, and the hardwood industry is no exception. Over the past 30 years, most of the hardwood industry has adopted new technology to help improve efficiency and quality in one form or another. This is a positive move as long as things are kept up-to-date and monitored.
One of the biggest challenges is keeping new processes in check and monitoring the manufacturing results from this new technology. There are several ways to keep things in check, and NHLA would like to help in any way it can.
One way that NHLA can help is by training employees that are monitoring the Grades being produced by the mill or consumed by the manufacturer.
NHLA can also assist by offering a Quality Control program. The Program monitors different areas of the production process to assure that the high rates of production are actually producing a profitable product, utilizing as little raw material as possible.
The NHLA Inspection Services Team can and does actively evaluate member company Inspectors for Grade accuracy as well as types of defects found in the lumber. During an evaluation the NHLA National Inspector can identify certain defects that are caused by different processes that affect the Grade and recovery.
The NHLA National Inspectors can perform tests on the following processes in the production of lumber:
• Debarker • Dip Tank • Edger and Trimmer • Kiln Operation • Log Scale • Lumber Thicknesses • Minimum Opening Face • Package Appearance • Pallet Cants • Ripsaw • Yard Packaging
These are the standard processes that the team can test but we have the ability to design testing in other areas of your operation as necessary.
If you are interested in speaking with someone about monitoring your processes, please contact me.
Dana Spessert, NHLA Chief Inspector can be reached at 901-399-7551 or by email at [email protected].
–by Dana Spessert, NHLA Chief Inspector
Over the years, there have been numerous studies on soft maple and other species that show signs of impact staining, often times referred to as “bruising”. This impact staining is a form of oxidative stain, which in many cases is not easily identifiable when the board is rough and only reveals itself upon surfacing.
Studies show, that in the case of soft maple, bruising can be caused by impacts from a hammer. If this is true, then one can assume that any extra force that is exerted onto the log or sawn boards would cause the wood to become discolored in the areas of impact.
There are two studies on this subject, that may be of interest.
- Exploring Methods for Prevention of Oxidative Stain in Soft Maple (https://www.fpl.fs.fed.us/documnts/fplrp/fpl_rp654.pdf)
- Factors Affecting Oxidative Stain in Soft Maple (Acer rubrum L.) (https://www.fpl.fs.fed.us/documnts/fplrn/fpl_rn311.pdf)
It has been my experience that for certain species like soft maple and birch, the use of knurled or screw rolls with excessive hydraulic or air pressure can cause this same type of bruising on the boards after drying. One could also assume that the use of modern-day hydraulic log loaders can also exert extreme pressure on the logs and create the same type of damage to the wood.
I would suggest that when sawing soft maple or birch, you reduce the pressure of the press rolls on the edger, gang saw, re-saw and any other area of the sawmill with press rolls, to reduce the bruising effect that is downgrading the lumber through the process. I realize that there may be safety concerns with the decrease of pressure, but I believe that with some simple studies, there is a pressure that will fill both requirements.
I would also like to address the effects on grading lumber that has been “bruised” by a process such as described above. When grading hardwoods, the Inspector shall grade the lumber as he/she finds it as described on page 4, paragraph 4 of the NHLA Rules Book:
“Lumber shall be inspected and measured as the inspector finds it, of full length, width and thickness. No allowance shall be made for the purpose of raising the grade, except that in rough stock, wane, and other defects which can be removed by surfacing to standard rough thickness shall not be considered. Nothing herein shall be construed as prohibiting the shipper from improving the grade or appearance of the lumber at time of or prior to shipment.”
With the Rule as listed above, the shipper is not allowed to overlook stain. But if it does not show on the surface and only appears after surfacing, then the Inspector would have no other option than to inadvertently cut over it in a clear face cutting. I would caution Lumber Inspectors who have had samples of bruising returned to them, to closely watch the rough lumber. I believe, in many cases, there were signs of the bruised areas that can and should be identified on the surface during the grading process.