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Author Topic: Pressure Treating Pine  (Read 5733 times)

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Offline Tim L

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Re: Pressure Treating Pine
« Reply #20 on: January 12, 2009, 05:39:46 PM »
Thanks Dang ,I'm not familiar with Penta . What is it ?
Do the best you can and don't look back

Offline customdave

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Re: Pressure Treating Pine
« Reply #21 on: January 12, 2009, 08:58:12 PM »
TimL, Penta is an old treating that you soak timbers &posts in , the longer you leave it the better. This product was outlawed years ago, envoirmentel issues I suppose its a darn good treating for pine, spruce, tamarack. I'm looking for recipe as I can obtain in crystal form.It has to be disolved in methonal first then added to desial fuel, just need to know these mixtures ?          customdave
Love the smell of sawdust

Offline Theron211

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Re: Pressure Treating Pine
« Reply #22 on: January 10, 2020, 10:30:44 AM »
Does anyone have any leads on a company that will Pressure Treat in the NY, CT, PA, NJ area?  Thanks in advance.

Offline rastis

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Re: Pressure Treating Pine
« Reply #23 on: January 10, 2020, 12:48:13 PM »
Check with Northeast Treaters in Belchertown, MA

Offline GeneWengert-WoodDoc

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Re: Pressure Treating Pine
« Reply #24 on: January 11, 2020, 10:32:04 AM »
There are different levels of treatment...more chemical is needed when the wood will be in contact with the ground than when above ground.  Incidentally, PT usually uses a vacuum first to pull out the air and then when the vacuum is released, the wood sucks in the preservative and the added pressure pushes in a little more.  Then, a slight vacuum at the end pulls out any loose preservative near the surface so the surface looks dry and has less  oozing out of preservative initially.  

The depth of treatment is also a factor...for large timbers, like a railroad tie, the chemical is measured in the outer 2 and not the core.

The reason for drying is twofold. First, when you dry, the wood may warp or crack or otherwise lose grade or quality.  So, after the first drying, the "defective" pieces are withdrawn and not treated as it would be a waste of money.  Second, to get the chemical into the wood, the water has to be removed so there is room for the chemical and the water or other liquid that carries the chemical into the wood.

Some people do pressure treat wetter wood.  They put as much chemical in as will go in...usually not much.  It is called "treating to refusal."  It looks good on the outside, but is of little value.  So, this is usually considered to be fraudulent and will not have a legitimate treating label or stamp.

If you dry wood to an average of 20% MC, the core may be still too wet for much chemical, but the outside will absorb a lot creating a barrier for entry of bugs or decay, until the wood cracks deeply, is drilled into, has a nail inserted, has an end cut, etc.  All of these expose untreated wood.  Sometimes drilled holes are swabbed with preservative before having a screw or bolt inserted.  Likewise, fresh cuts are treated with preservative before use.

If you dry under 20% MC, you will get more retention of chemical, all else being equal.  This is expensive, but for ground contact may be worth it.  At 25% MC retention can be less, but still ok for above ground.  The treater can also vary the retention amounts by the way the equipment is operated.  Even so, if the MC of incoming wood varies greatly, preservative amounts will vary.

The chemicals used for treating can vary...not all PT is the same.  Government control.

After treating, the wood must be "dripped dry" and the chemical that drips off is recaptured.  Sometimes, to get better retention and lock the chemical in the wood better, and get an drying defects to show up, the wood is also kiln dried after treatment (KDAT) at certain temperatures.  Costly but worth it for some uses.  Sometimes we are concerned about residual chemical deposited on the surface as it can rinse off in the first rain storm.

A key consideration when doing PT is the cost of failure of the treated wood.  That is, if the failure causes a deck to fall and injure people, or the fence post fails and expensive animals escape, or a tie fails and a train wrecks, it is worth the cost to have a well treated wood product.

Mention should be made that scrap and sawdust from treated wood should never be allowed to be on the ground or left on the building site, as the poison will be available for animals and people to come in contact with it and it can seep into ground water.  Therefore, capture treated wood debris and dispose of properly (municipal dump landfill sites are ok, at least last year).  In a playground that uses treated wood, it is especially critical to avoid sawdust and other debris etc.

Using oil is likely to increase flammability (issue with a grass fire), plus gravity and heat from the sun will pull the oil down the post and into the soil.  Not good.  Probably illegal due to the environmental damage.  Ever wonder why creosote treated poles have a dark ring in the soil around them and the upper sections appear to have little creosote?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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