Thread: Determining timber dryness - the kitchen oven experiment

Good Morning Brett

One minor quibble about your mathematics. The moisture content should be calculated relative to the bone dry weight, not the wet weight. Thus in your first example, rather than a moisture content of 9.76%, I would calculate as follows:

Moisture content = [( wet weight / dry weight ) - 1 ] * 100

= [ ( 37.9 / 34.2 ) - 1 ] * 100

= 10.82%

When you think about it, the bone dry weight is the only constant in the process.



Fair Winds

Graeme

Thanks for that Graeme. I'll change the calcs (but I won't bother putting them up here again).

Brett, I have a meter if you want a reading.

I might just spin over one of these days Ken. Cheers.

It would be interesting to put a meter over it - and see how it compares with the posted oven calc's.

My money would be on the meter.

I recall with the impedence tramex wood encounter... on dry 6 x 2 Jarrah - at 12% emc - if you put your hand under the plank thru the 2 inch thickness you can watch the needle on the meter go up over 20% as it "detects" the moisture in your hand thru 2 inches of Jarrah.

They are surprisingly sensitive and accurate if you apply the corrections for species, and temp.

Originally Posted by John.G

Tallowwood is I believe schedule USDA schedule T3-C2 or British schedule C


Table 16 T3-C2
Temperature Equilibrium Temperature
Moisture Dry- Wet- moisture Relative Dry- Wet-
Step content bulb bulb content humidity bulb bulb
MC dry/ wet F EMC RH Drybulb/wet bulb celcius
1 Above 40 110 106 17.6 87 43.5 41.0
2 40 to 35 110 105 16.3 84 43.5 40.5
3 35 to 30 110 102 13.6 76 43.5 39.0
4 30 to 25 120 106 9.9 62 49.0 41.0
5 25 to 20 130 100 5.7 35 54.5 37.5
6 20 to 15 140 90 2.9 15 60.0 32.0
7 15 to Final 160 110 3.4 21 71.0 43.5
Equalize and condition as necessary (see appendix A).


"Oven drying in times gone by was the absolute definitive reference for determining Moisture Content (MC) in serious timber seasoning operations. There are in principle three methods available. Oven drying, Microwave and Infra Red. We will deal here with only Oven Drying."

And oven drying of test samples is still the only method of testing moisture content that will stand up in court in the event of a dispute

Thanks John

Probably a little highbrow for our type of operation. I was looking at the details to try and judge whether tallowwod was a difficult or easy timber to dry as I have not had any dealings with it until I obtained some from Mapleman about the same time as Brett.

Regards
Paul