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Author Topic: Sterilize air dried wood  (Read 2565 times)

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Offline flatrock58

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Sterilize air dried wood
« on: June 14, 2017, 08:54:06 am »
I have read many post about the benefits of kiln drying wood and sterilizing it to kill powder post beetles.  I was wondering if you could sterilize air dried wood without kiln drying it.  That would allow you to sell air dried wood free of bugs, but not spend all the time kiln drying the wood.
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Offline PC-Urban-Sawyer

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Re: Sterilize air dried wood
« Reply #1 on: June 14, 2017, 10:17:11 am »
And what method would you use while air drying enable you to assure the buyer that the wood is free from "bugs" ???

Rereading your post, I believe that that is actually your question...

Good Luck!

Herb

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Re: Sterilize air dried wood
« Reply #2 on: June 14, 2017, 11:19:53 am »
We sterilize green or air dried wood all the time to prevent insects in the tree from being transported to another country. The PPB does not like the high MCs (30%MC or higher) seen in air drying, so there is a small risk for this insect. Other insects like the higher  MCs.

However, if you were to heat the wood to 133 F throughout the piece, that only kills existing insect infestations, but does not prevent new infestations. Therefore, you could not be sure that the lumber you sell is bug free,  as it could get infected after treatment
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline flatrock58

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Re: Sterilize air dried wood
« Reply #3 on: June 14, 2017, 11:51:48 am »
Gene.  I was thinking of building a 10' x 6' x 6' insulated box.  Then I could sterilize it after it had been air dried down to 14% or so.  I am also planning on building a solar kiln and need a way to sterilize wood after it is dry.   This would give me a way to sterilize both air dried and kiln dried wood.
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Online GeneWengert-WoodDoc

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Re: Sterilize air dried wood
« Reply #4 on: June 14, 2017, 10:07:05 pm »
That would work
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline tawilson

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Re: Sterilize air dried wood
« Reply #5 on: June 15, 2017, 07:14:05 am »
Gene.  I was thinking of building a 10' x 6' x 6' insulated box.  Then I could sterilize it after it had been air dried down to 14% or so.  I am also planning on building a solar kiln and need a way to sterilize wood after it is dry.   This would give me a way to sterilize both air dried and kiln dried wood.
Curious as to what you are using to sterilize it?
Tom
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Offline WDH

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Re: Sterilize air dried wood
« Reply #6 on: June 15, 2017, 07:35:17 am »
I bet that it is heat. 
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Offline flatrock58

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Re: Sterilize air dried wood
« Reply #7 on: June 15, 2017, 10:49:01 am »
Haha.  WDH is right.  But what kind of heat.  Read some post where Yellowhammer was using halogen heat lamps.  Also I have a gas furnace I could rig up.  Will try the heat lamps first then go from there.
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Offline tawilson

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Re: Sterilize air dried wood
« Reply #8 on: June 15, 2017, 04:08:07 pm »
Okay my rookie status is showing. I assumed kiln dried was using heat and you were using something like a borax solution.
Tom
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Offline samandothers

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Re: Sterilize air dried wood
« Reply #9 on: June 15, 2017, 05:22:33 pm »
I had thought about building a heat chamber also, but that is close as I got to buildingone. I was going to use a thermostat that could be programmed for a band of temperature to allow 150 or 155 as max.  The sensor then place in the unit near the center and on the bottom of the stack.  I had some input from another member about using a oven heating element to supply the heat.  I understand there is a need to have the air circulated to even the temps.  Make sure the equipment you use can withstand the temperatures.

I look forward to hearing how your build goes and the chamber performs.

Offline flatrock58

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Re: Sterilize air dried wood
« Reply #10 on: June 15, 2017, 05:26:54 pm »
Tawilson. The Haha was for WDH for trying to be funny. 
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Offline Kbeitz

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Re: Sterilize air dried wood
« Reply #11 on: June 16, 2017, 02:25:03 am »
I bet sulfur candles would work...

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Offline YellowHammer

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Re: Sterilize air dried wood
« Reply #12 on: June 16, 2017, 08:43:56 am »
Haha.  WDH is right.  But what kind of heat.  Read some post where Yellowhammer was using halogen heat lamps.  Also I have a gas furnace I could rig up.  Will try the heat lamps first then go from there.
The only reliable and safe thing I have used are sealed, halogen work lights.  They are every inefficient and convert a lot of their electrical input into heat.    Any heater with a fan, such as a dedicated space heater, milk parlor heater, etc will die within weeks, sometimes days, due to the nature of the air.  They also have safety thermostats which will turn them off prematurely when the area gets too hot.  I have tried many things, and halogens work lamps will last for a year or more before I have to replace the bulbs for about $5 each.  It's very important to make sure not to create hots spots over of around the lamps and risk a fire, so I always put them in front of the kilns fans away from combustibles.  Since they are sealed, they are impervious to the kiln moisture and corrosive environment, and can be purchase for about $20 each at Lowes or HomeD
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Re: Sterilize air dried wood
« Reply #13 on: June 16, 2017, 08:14:31 pm »
You might call your insurance company to make sure you are covered with fire insurance with any heater that you use. Avoid the use of the word kiln, as they will think it is a ceramic kiln that gets really hot.

Remember that the PPB is inside the wood, so any chemical or fumigating gas or heat must penetrate throughout the entire piece of wood, not just the surface.  When using heat, remember that fine dust ignites at maybe 250 or 300 F.  Keep the chamber free of dust indeed.

Maybe you can find an small, old, closed trailer for heating.  Insulate it, of course.  A household furnace using propane could be used for heat with control modification but it does require oxygen to work, so the best is probably using a plenum duct rather than putting it into the chamber.
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Offline PNWRusty

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Re: Sterilize air dried wood
« Reply #14 on: June 29, 2017, 05:24:43 pm »

The only reliable and safe thing I have used are sealed, halogen work lights.  They are every inefficient and convert a lot of their electrical input into heat.   

Halogen's and all electrical lights convert 100% of the electrical input into heat. Even the light they produce is converted to heat once the light hits an object (or the air for that matter). A 500W light produces 500W of heat.

Offline YellowHammer

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Re: Sterilize air dried wood
« Reply #15 on: June 29, 2017, 11:00:53 pm »

The only reliable and safe thing I have used are sealed, halogen work lights.  They are every inefficient and convert a lot of their electrical input into heat.   

Halogen's and all electrical lights convert 100% of the electrical input into heat. Even the light they produce is converted to heat once the light hits an object (or the air for that matter). A 500W light produces 500W of heat.

Yes, the first law of Thermodynamics is still in effect even for light bulbs, but that's not the whole story.  I'm talking about luminous efficiency, or more correctly, luminous efficacy (lumens per Watt), and the increased amount of electrical energy required for inefficient types of light bulbs to produce the same amount of visible light.

The two most likely general types of light bulbs that make a reasonable heat source in a kiln are incandescent and halogen.  Sodium and others may work, but have packaging issues I don't want to deal with.

Incandescent lamps typically have short life spans and use significantly more watts than compact fluorescent lights and halogen lamps to to produce the same lumens, or light output. More than ninety percent of the energy used by an incandescent light bulb escapes as heat, with less than 10% producing light. https://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact%20Sheet_Lighting%20Technologies.pdf

Halogen lamps are slightly more efficient than incandescent lamps, but operate at a much higher lamp temperature. These high operating temperatures can present a safety concern in some fixtures, some of which consume as much as 500 watts each.

Since these two types of bulbs have a relatively low luminous efficacy, they require more electrical energy to achieve the same amount of visible light.  The less efficient the light bulb, the more energy required to produce the same amount of visible light, so more Watts per lumen, or more energy required per lumen, or ultimately, more heat generated per lumen, which is exactly opposite of the corporate light bulb makers strategy.  They want a highly efficient light builb that only uses minimum electricity to produce the same amount of visible radiation. 

With incandescent, its rare to get the high wattage levels found in common and cheap halogens.  Most incandescent lights max out at about 100W, and even heat lamps, which may have a higher rating, rarely get to 500 Watts, or the rating of a single halogen.  Most incandescents are not in weatherproof housings, so don't last long in a kiln environment.  These are not a good, long term approach to heating a closed space.

So my preferred and cheap way to generate safe heat from electrical energy, barring actual heat strips, which are an electrocution hazard, is to simply use multiple halogen lights.  So instead of using five 100 Watt light bulbs, and all the associated weatherproof fixtures associated with it, I prefer to use sealed, weather proof 500 W halogens, which are commonly found at any Lowes or Home Depot.

This reference uses the phrase, "buy lumens, not Watts"
https://energy.gov/energysaver/lumens-and-lighting-facts-label
However, for heating a kiln, "buy Watts, not lumens."


   
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Offline farmfromkansas

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Re: Sterilize air dried wood
« Reply #16 on: August 06, 2017, 05:04:59 pm »
I'm looking at getting an old reefer trailer, of course they are taking the cooling unit off, so it will have a hole in the front to frame in.  Considering making a shelf for my space heater to sit on, and cut a hole for the space heater to shoot the heat inside, and opening a small vent down low in the opposite end.  This is to keep the heater from shutting down the way they do when inside the chamber, and make it get the inside of the trailer hot enough to kill all bugs and eggs.

Offline scsmith42

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Re: Sterilize air dried wood
« Reply #17 on: August 06, 2017, 08:17:34 pm »
FWW magazine had an article several years ago about a simple home sterilization chamber that used foil backed foam board and a space heater. 

A paraphrased version is attached.

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Re: Sterilize air dried wood
« Reply #18 on: August 07, 2017, 07:16:58 am »
Because the air temperature in a sterilization chamber must be 150 F or even hotter in order to get the wood up to 133 F throughout the piece, the insulation must be able to safely withstand the high temperature and the heater must be able to get the air that hot as well safely.  You also need a high temperature limit switch that will shut the unit off if something goes wrong and it overheats, especially if the sterilization chamber is in a house or shop that could be damaged by fire.  Also, oftentimes, home owner's insurance will not cover damage caused by an accident in a business operation that is operated inside the home.  Bottom line is to be very safety conscious.

Note that although solid wood might need to be around 450 F to ignite, fine dust will ignite at much lower temperatures.  Many possible heaters will be hot enough to ignite dry wood dust that would accumulate in the chamber.
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Offline farmfromkansas

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Re: Sterilize air dried wood
« Reply #19 on: August 07, 2017, 06:51:35 pm »
Would it be better to build a solar collector on the south side of the reefer trailer?  Plan to position it long ways east and west.