Time to Kiln-Dry 12/4 White Ash

Estimates on the time required to dry a load of White Ash sawn three inches thick. March 28, 2010

Question
I am well aware that this is a very vague question and that many unlisted/unknown factors can influence the answers. However, I am just looking for a general, approximate answer to see if I am in the ballpark. Roughly what can be expected - timeframe wise - to kiln dry white ash (Pennsylvania) to approx 8% that is loaded into the kilns with no significant air drying time. The drying schedule was started using a T3 & B2 schedule, and the average MC of the four samples cut when loading the kiln were 38%, 41%, 46% 44% (air flow is an even 300 fpm across the charge)! Thank you all in advance. Again I know it is vague and all the info isn't needed please don't reply what info isn't listed. I’m just looking for a rough timeframe.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
In most cases 4/4 white ash, for best color (whitest), is dried using T5-B5. With that schedule, it will take about ten days, including equalizing and conditioning for "tree-green" to 8% MC. However, the "tree-green" MC of ash is around 95% MC. So, you do not have green MCs, but have already lost 2/3 of the MC (unless you are using an electric MC meter to measure MC, in which case it will read in the 35% MC range even though it is 95% MC). The drying time for 12/4 is about 4.38 times longer than for 4/4, according to Drying Hardwood Lumber.


From the original questioner:
Thank you for the reply Gene. I have a copy of the Drying Hardwood Lumber, and we have been through it many times (very helpful book). I do not think that we have lost 2/3 of the moisture content in this lumber prior to being loaded into the kilns. There was very little AD time on this lumber at all, or between cutting the timber and then the logs. The average MC that we found in the samples the day the kiln was loaded was low to mid 40%.

Going by the Drying Hardwood Lumber book that is pretty much right where it should be for white ash (Page 65 shows the moisture content for green - white ash; heartwood and sapwood to be 46% and 44%. Are those numbers listed in the book correct? I don't recall seeing anywhere in this book that says the moisture content for fresh white ash would be 95%).

Also these moisture contents were calculated by doing oven tests on pieces that contained heart and sapwood - very good representation of the kiln charge. Looking at how this charge is doing we seem to be on pace for approx 50 days down to 8%. So I guess we are in the ballpark, but can you please clarify for me the moisture content on white ash - fresh from the saw?


From Gene Wengert, forum technical advisor:

I was looking at Table 2.1 which gives much higher numbers. I checked and indeed this table is incorrect for white ash; the numbers given are for aspen. Sorry for the confusion. Incidentally, this table also has the titles reversed for sapwood and heartwood.

From contributor O:
True. I use 42% for the green MC of white ash in PA. Due to the low MC, I am fairly aggressive with ash but I run vacuum kilns. It takes me 12 days to dry 12/4 so you are looking at a month in a conventional kiln, I would guess.

From contributor Y:
I dried 13/4 ash and it took me 53 days in a conventional kiln.

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