Blue Stained Pine (prevention)

[Deadwood]

On another forum there was some discussion started about White Pine and the blue stain that can occur in the summertime. Perhaps I am mistaken, but I belieave a sawmill near me that deals ONLY in White Pine sprays their lumber with water to keep this blue stain from forming. It was stated that they spray water to reduce shrinkage and cracking, which I concur happens at hardwood mills a lot, but White Pine is pretty stable. I was always told this sawmill sprays their logs with water to keep out the dreaded blue stain. Is this correct?

I am not that knowledgable about White Pine's blue stain but perhaps some of you that are could inform me about this potential defect.

[Tom]

SYP is sprayed with water, or submerged, to stave off blue stain and insects.  Blue Stain requires a specific moisture content to grow.  If the wood is above or below that window, it won't.  Insects don't like the water running on the logs either.  Blue stain is the result of the inoculation of the log by a bark beetle.  If the beetle can be kept off of the log then there won't be blue stain.  I imagine that white pine is attacked in the same manner.

I asked this same question to a forester at the pulp mill here years ago and got that answer. 

I've sawed SYP that was laying on the ground for over a year that didn't have blue stain and I've sawed some that was felled within days of sawing and it did have blue stain.  I've attributed this to the forester's comments.  People have asked me if their logs will have blue stain and how long they can let them sit before sawing and avoid the stain.  I tell them this story and comment that the chances of blue stain are great but that you can't just associate a time frame with the fungus.

When it takes off in a log, it is only a matter of hours before it reaches the heart though. It's fast stuff.

[SBarrows]

Blue stain fungi require a relatively high temperature and humidity, and oxygen to grow. Watering logs attempts to serve two purposes. One is to keep the temperature lower by evaporation on the log surface, and the other is to keep the log "drowned", preventing a source of oxygen for the fungi. As you can now imagine, the problem is keeping enough water on the logs to not allow any oxygen, and having the conditions for evaporation on the surface. Another problem also arises, in that the log remains saturated.

In my experience drying 15MMBF of white pine annually, the best method to prevent blue stain is to get the wood drying as soon as possible. Stain can start in a matter of hours, so getting air around the log helps its surface to start drying, but the best thing is to get it turned into lumber in less than two weeks, and on sticks and drying, preferably in a kiln, but at least under cover of some sort and with some sort of air circulation. The lumber needs to be below 30% e.m.c. to be safe from stain, but as long as the surface is starting to dry, you are in much better shape.

There are some chemicals that also work somewhat, that is a whole nother discussion. Many large white pine mills do water logs, but a getting lumber immediately into a good dry kiln is very critical.

In some cases, if you are dealing with lower volumes, if you can stain the logs and feed the bugs, and are good at marketing, you can sell it as character wood, ($$) but that is difficult to do by the millions of BF.

Good luck.

[Snag]

I dont want to hijack the thread, but what about attempting the opposite?  I would actually like to get some blue stained pine.  What would be the best method to achieve this?  Also, how do you keep the logs from being chewed to swiss cheese while doing so?

[kderby]

Hi Snag, no worry about hijacking the thread.  Bluestain is a blessing or a curse depending on perspective and product.  I have a customer that can not have bluestain and others that desire it.

The explanations of bluestain prevention listed above are accurate.  Temperature is critical.  The application of cooling water (evaporation) during periods of time where air temperature is above seventy degrees halts or slows the development of the fungal activity and thus the blue coloration.

If you want blue stain it is not a function of time alone it is a function of time and temperature.

I mill a fair bit of bluestain ponderosa and I want to comment on two things. First, intentionally pushing logs to bluestain degrades the market value of the logs.  Second, bluestain is an organic event, difficult to control and highly variable.  Bluestain logs here go for one quarter the price of brite logs.  If you are taking prime logs and allowing them to enter the initial stages of decay I would wonder if that is a good choice.  There is a fine line between bluestain and rotten.  The fungus as it works through the wood is utilizing components of the wood to grow.  At some point the wood goes from being colored to corrupted.  I have milled some 1x10 pine, sixteen feet long, clear lumber with a light blue coloration.  Very nice, but there is no way I could produce another fifty board feet of that material intentionally.  That variability makes the lumber produced limited in its scope of application.  If you have the logs and the temperatures that have resulted in bluestain, don't be afraid to mill them and enjoy the variety of the coloration.  If the logs are "brite" mill them or sell to a mill then buy twice the volume of blue logs with the money generated.

Just my two cents worth.  Thanks for asking the question.  We all learn from the questions and the answers. 

KD

[Tom]

It can be easy to confuse Bluestain  with a blue stain.  Bluestain fungus does not degrade the strength of the wood.  It's the brown rots and white rots that will destroy the wood.  A fairly concise PDF on the subject can be found on this link.  It is a Forest Products Laboratory produced document.