Silly idea

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08-27-2023, 9:44 AM
Bobby Hunt

Silly idea

I posted earlier about milling loblolly pine to use as non structural building materials and I’m trying to come up with a cost effective means of setting the pitch. From what I have read pitch will set at any temperature up to that temperature. Say 100 degrees for 48 hours will keep the pitch solid up to 100 degrees forever. Over 100 and it’ll start to liquify again. 100 seems like a lot but the surface of a piece of wood exposed to a window or even the sun during the summer can get there in a hurry. The room temperatures may be cool but say a foot of baseboard directly across from a window could get pretty hot pretty quick. Nothing pretty about pitch oozing out of your nice baseboard LOL.

With that in mind it seems like a small, well insulated nearly airtight structure with a couple of space heaters inside would do the job over a couple of days. I’ve read that 160 degrees is ideal for most uses over a 24-48 hour period. I don’t think a couple of 3 or 4 1500 watt space heaters would get a 10x5x5 “box” to 160 degrees but I think in the summer in the south they’d easily maintain 100 degrees for days and days. It’d be akin to a hot box on a job site…one 100 watt bulb will boil a can of soup in about 4 hours….I’ve eaten a heap of meals heated that way. Anyone have any thoughts? Crazy? Shear ignorance? I’ll own that…there is far more I don’t know than know!
08-27-2023, 3:49 PM
John TenEyck

Space heaters are designed with a high temperature thermostat that trips at around 130F, IIRC. I use an old school one w/o that feature in my lumber kiln and I can easily get to 140F and hold it there for 24 hours, long enough to kill any bugs that are present. I doubt it would do well going to 160F, however, but there are plenty of other electrical heater systems that will. Look in McMaster Carr and you will find all kinds of electrical heaters designed for higher temperatures.

It can be done, but you will want to do it away from other structures you care about and install a high temperature cutout and alarm, just in case.

John
08-28-2023, 6:58 PM
Bobby Hunt

Quote:

Originally Posted by John TenEyck

Space heaters are designed with a high temperature thermostat that trips at around 130F, IIRC. I use an old school one w/o that feature in my lumber kiln and I can easily get to 140F and hold it there for 24 hours, long enough to kill any bugs that are present. I doubt it would do well going to 160F, however, but there are plenty of other electrical heater systems that will. Look in McMaster Carr and you will find all kinds of electrical heaters designed for higher temperatures.

It can be done, but you will want to do it away from other structures you care about and install a high temperature cutout and alarm, just in case.

John

I figured I’d have to hack the internal thermostat and break the circuit through a line voltage thermostat and contractor. What are the dimensions of your kiln? From what I understand the pitch will “set” at the highest temperature and stay set until it is exposed to a higher temp. If that is the case it’d be hard to imagine a piece of trim inside a house getting above 100 degrees.
08-28-2023, 7:08 PM
Malcolm McLeod

Don't neglect simple sunshine - - depending on seasonal factors and your location, you can get dangerously high temps with a simple greenhouse effect and some black (painted) surfaces to absorb heat. In desert SW, I have aimed a non-contact thermometer at OD green tanks and recorded surface temps of 126F on a 95F (air) day; black iron pipe will yield 2nd deg burns to hands. Parked cars in N.TX easily hit 140F in 20min of full noon sun.
08-28-2023, 9:17 PM
John TenEyck

Quote:

Originally Posted by Bobby Hunt

I figured I’d have to hack the internal thermostat and break the circuit through a line voltage thermostat and contractor. What are the dimensions of your kiln? From what I understand the pitch will “set” at the highest temperature and stay set until it is exposed to a higher temp. If that is the case it’d be hard to imagine a piece of trim inside a house getting above 100 degrees.

My electric kiln is 12 x 4 x 4 ft, and can handle about 400 bf of 10 ft lumber. It's in an unheated shed, so it's insulated with 3-1/2" of fiberglass plus 2" of foam board on the inside. The oil filled radiator I use to heat it has a max. output of 1500 W, and that's more than enough to heat the wood to 140F. I've never tried to go higher than that.

I use a small digital controller to run the heater, like this: https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1
You set the radiator for max heat output and the controller modulates it as needed. You can use a dehumidifier with it, too, controlled in the same way.

John
09-08-2023, 11:43 PM
Bill Dufour

Climate? My roof deck gets to 135 on warm days here. More on hot days when it is over 100 or so air temperature. How hot is you attic on a warm day?
Bill D
09-09-2023, 10:42 AM
John TenEyck

Quote:

Originally Posted by Bill Dufour

Climate? My roof deck gets to 135 on warm days here. More on hot days when it is over 100 or so air temperature. How hot is you attic on a warm day?
Bill D

Probably doesn't stay there long enough for the internal temperature of the lumber to get very close to that, however. Same with an attic. The thermal conductivity of wood is pretty low, so it takes a long time for the internal temperature to approach ambient. This is the same reason solar kilns won't work for killing bugs in lumber.

John
09-12-2023, 12:44 PM
Bobby Hunt

Quote:

Originally Posted by John TenEyck

Probably doesn't stay there long enough for the internal temperature of the lumber to get very close to that, however. Same with an attic. The thermal conductivity of wood is pretty low, so it takes a long time for the internal temperature to approach ambient. This is the same reason solar kilns won't work for killing bugs in lumber.

John

This was my understanding, that the wood had to be exposed for a prolonged period of time at a high temperature to set the pitch and kill insects. That being said I have talked to several people who have used SYP off portable mills air dried for a couple of months in the deep south for ship lap and flooring and have had no problem with pitch or insects. It used to be commonly used, green as a gourd, to build with. Many of those structures are still around to day. We currently live in a row house in a HOA community and I will bet a coca cola none of those houses last 50 years without some major structural work being done.