Kiln dried Firewood - The future ?

[Chalgravesteve]

As a firewood user, I wouldn't buy kiln dried, personally. My local supplier offers kiln dried ash or air dried birch. The birch is cheaper, better for the environment and burns beautifully.

 

Plus if I sit my lovely kiln dried logs outside (even under cover) for a few weeks over winter, will they not fairly swiftly re-absorb atmospheric water until they're the same MC as air dried logs in the same situation?

 

We are currently conducting and experiment to see how long it takes a kiln dried log to reabsorb moisture. As far as we can make out, we will all be dead before we get a reading at 25% MC again. It is not like a sponge, once the moisture has been expelled, the rate at which it returns to the wood is massively significantly slower.

 

If dried wood just absorbed it back at the same rate, furniture, general untreated timber in sheds and other outdoor uses, would just get sodden very quickly. The reason the moisture is there in the first place is because the tree was alive and drawing sap/moisture through the trunk as part of its growth process. It's now dead. That process no longer happens.

 

Take your Christmas Tree cut off above the root, stood in water for three weeks or so. You might sustain it for a few weeks that way, but the end result is the same. The tree died when you cut it off at the root, and the ability to absorb moisture immediately started to slow at that point until it stopped completey.

[sandspider]

Hi Steve

 

I get what you're saying, but I was talking more about reabsorbing water until it's as moist as air dried wood. I imagine kiln dried would take longer to equilibrate with atmospheric moisture than air dried, but they'd both get to roughly the same state in time? Interesting to see that it is quite slow to reabsorb though.

[Woodworks]

We are currently conducting and experiment to see how long it takes a kiln dried log to reabsorb moisture. As far as we can make out, we will all be dead before we get a reading at 25% MC again. It is not like a sponge, once the moisture has been expelled, the rate at which it returns to the wood is massively significantly slower.

.

 

Not surprised your kiln dried does not go back up to 25% as this is too high for equilibrium with the atmosphere. We dry most of ours down to 20% air dried. Can't get much lower than that in a soggy winter mind.

 

This chart will tell you what it could go back up to for a given temperature and RH Wood Equilibrium Moisture Content Calculator from Wood Workers Source.com

[Logsnstuff]

there is a merchant on fb refers to air seasoned logs as being 30-35% where his kiln dried is under 20% so better value. I asked him why my air seasoned logs at 15% were not as good as his kiln dried at 20% but he didn't bother to answer.

[Chalgravesteve]

Not surprised your kiln dried does not go back up to 25% as this is too high for equilibrium with the atmosphere. We dry most of ours down to 20% air dried. Can't get much lower than that in a soggy winter mind.

 

This chart will tell you what it could go back up to for a given temperature and RH Wood Equilibrium Moisture Content Calculator from Wood Workers Source.com

 

I didn't say it has gone up to 25%. I said we would all be dead before it gets near it, it will take that long. We kiln dry to around 15/16% MC in about 7 days. We have a number of logs under test that we took out in February at 15%. They havent moved yet. They still show 15%. I would expect them to take something back up over time, but my customers use the stuff I deliver within a few months, they don't store it for a year or more. Even if they did, I wouldn't expect the logs to get anywhere near 20% based upon what I have seen so far.

[cornish wood burner]

We are currently conducting and experiment to see how long it takes a kiln dried log to reabsorb moisture. As far as we can make out, we will all be dead before we get a reading at 25% MC again. It is not like a sponge, once the moisture has been expelled, the rate at which it returns to the wood is massively significantly slower.

 

How are you feeding the moisture? As we know moisture loss is very dependant on air flow, are you trying to rehydrate with the same airflow? Our biomass winter chipping of softwood cord, after significant rain seems to produce wetter chip than in the summer. Some I put down to surface moisture but if what you are saying is correct then it may be all surface wetting, or does kiln dried react very differently to air dried?

[Chalgravesteve]

Hi Steve

 

I get what you're saying, but I was talking more about reabsorbing water until it's as moist as air dried wood. I imagine kiln dried would take longer to equilibrate with atmospheric moisture than air dried, but they'd both get to roughly the same state in time? Interesting to see that it is quite slow to reabsorb though.

 

Yes, I don't disagree that the kiln dried stuff possibly would make it back up to the level of air dried wood over some as yet unknown period of time. It may not though. It might be that the force drying process has changed some element of the way that the log reacts to the atmospheric moisture.

 

The reason we are testing is because this is a new part of my business. We haven't done this before, but we are rapidly gaining some very good accounts, particularly some potential high volume wholesale accounts. In order to supply those accounts, we may need to start drying greater volumes during the summer period, to provide us with bulk stock ready for the Autumn supply times. I need to know that the stuff I dry March - September can be stored ready for delivery without the logs going outside the MC range I am guaranteeing to my wholesalers.

[Chalgravesteve]

We are currently conducting and experiment to see how long it takes a kiln dried log to reabsorb moisture. As far as we can make out, we will all be dead before we get a reading at 25% MC again. It is not like a sponge, once the moisture has been expelled, the rate at which it returns to the wood is massively significantly slower.

 

How are you feeding the moisture? As we know moisture loss is very dependant on air flow, are you trying to rehydrate with the same airflow? Our biomass winter chipping of softwood cord, after significant rain seems to produce wetter chip than in the summer. Some I put down to surface moisture but if what you are saying is correct then it may be all surface wetting, or does kiln dried react very differently to air dried?

 

I'm not "feeding" the moisture. I have a covered barn type building that has a reasonable airflow, so the logs we have already dried are stored in 2m3 wire mesh cages and stacked in the cages in the barn. My experiement is purely for my own wood in my own environment, to determine that wood I dried in April is still under the 20%MC I say it will be when I deliver it to the user. I am confident already that any increase in MC over a period of say 6 months, is going to be negligible. The stuff we dry in the winter, I expect to sell pretty quickly. I don't have vast areas to store stuff, nor the inclination to do so.

[cornish wood burner]

 

I'm not "feeding" the moisture. I have a covered barn type building that has a reasonable airflow, so the logs we have already dried are stored in 2m3 wire mesh cages and stacked in the cages in the barn. My experiement is purely for my own wood in my own environment, to determine that wood I dried in April is still under the 20%MC I say it will be when I deliver it to the user. I am confident already that any increase in MC over a period of say 6 months, is going to be negligible. The stuff we dry in the winter, I expect to sell pretty quickly. I don't have vast areas to store stuff, nor the inclination to do so.

 

 

Under cover I would not expect a sigificant rise if any above 20% even in winter.

That said I don't know your area so that could make a difference.

[arboriculturist]

If you are selling a quality product - good or bad - the average customer does not care how it is produced, just look at milk, poultry etc etc etc.

 

Those who kiln dry have a healthy competitive edge at the moment, which has to be accepted.

Those who don't, perhaps need to get better at what they do, to narrow the gap.