How hot should it be

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Forum topic by GuyK posted 12-30-2011 10:11 PM 1906 views 0 times favorited 7 replies Add to Favorites Watch
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356 posts in 4105 days

12-30-2011 10:11 PM

Topic tags/keywords: question milling

We at the farm are milling about 50 logs into lumber for our own use. We are going to make our own kiln using a portion of a heated greenhouse. My question is how hot should the temp be in the greenhouse to effectively dry the wood in a reasonable amount of time?

-- Guy Kroll

7 replies so far

View daltxguy's profile


1373 posts in 3940 days

#1 posted 12-30-2011 10:31 PM

Not too hot. I just read recently somewhere ( though I can’t recall where) that around 100F is sufficient. The key to drying wood in a kiln is moisture removal, therefore air circulation. Also, you don’t want to dry too fast. Too fast and the wood will check or honeycomb. Not enough air circulation and the wood may mold. So, it’s a balance between heat which helps to remove moisture and air circulation which carries it away.

I think much depends on what kind of wood you are drying too. It’s an art. Ring porous woods will dry faster through the ends, therefore prone to checking and honeycombing through too fast drying so these probably need to be sealed on the ends.

Having said that, don’t take my word for it – I’ve never dried wood in a kiln – only air drying and there I keep the wood in the shade but well ventilated. I dry mainly pines and NZ beech. The NZ beech needs very slow drying. The pines are mainly susceptible to growing molds in a high moisture environment but dry relatively quickly even at room temperature.

-- If you can't joint it, bead it!

View Nomad62's profile


726 posts in 2984 days

#2 posted 12-31-2011 12:31 AM

around 100 f is pretty typical, all the things daltxguy are right on. With decent ventilation and temp you can dry it well in 30 days or so.

-- Power tools put us ahead of the monkeys

View GuyK's profile


356 posts in 4105 days

#3 posted 12-31-2011 03:23 AM

Thanks Daltxguy and Nomad for your input. We are new to trying this so any information is a big help. 100F should not be hard to reach in the greenhouse. We are using a wood burning outside heating unit that provides lots of btu’s. Air circulation will be buy about 4 or 5 fans. I will let you know how it turns out.

-- Guy Kroll

View WDHLT15's profile


1747 posts in 2502 days

#4 posted 12-31-2011 02:56 PM

Drying wood in a kiln is a combination of both humidity and temperature, not just temperature. Google “Drying Hardwood Lumber”. That is a good resource and you will learn a lot about drying wood.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln.

View HalDougherty's profile


1820 posts in 3263 days

#5 posted 12-31-2011 06:59 PM

Here is a link to the best site on the Internet about solar kilns, plans to build one, how to use one, and construction photos.

You can also google “Virginia tech solar kiln” and find more information.

-- Hal, Tennessee

View Scsmith42's profile


125 posts in 2703 days

#6 posted 01-01-2012 05:59 AM

Guy, I’m a kiln operator. I second WDH and Hal’s advice re Gene Wengert’s “Drying Hardwood Lumber” manual as well as the Virginia Tech solor kiln manual.

Drying rates, temps, and RH% varies depending upon the species, thickness and initial moisture content of the lumber. 100F as a starting temp is acceptable for certain fast drying species, but is too hot for slow drying species such as oak, especially thick oak.

What species and thickness are you planning to dry, and will you be going straight from the sawmill into the kiln or air drying first?

-- Scott, North Carolina,

View GuyK's profile


356 posts in 4105 days

#7 posted 01-01-2012 01:36 PM

Thanks to everyone for all the good information. Scott I will be drying, Hemlock, Cherry, Maple, Oak, Ash, Walnut and Pine along with some Spruce. Thickness will be mostly 1 1/4 inch with some thicker stock, 2 to 3 inches. Yes it will be going straiight from the sawmill to the klin ( just a couple of days air drying ).

Scott if 100 F is to hot for slow drying species, do you have a temp you would recommend that would be a good average for all wood.

-- Guy Kroll

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