Moisture

[brainstrust]

Another newbie question.......what's a reasonable moisture % in wood to turn without worrying about cracking and warping? 6 to 8% ?????

[dai sensei]

Another newbie question.......what's a reasonable moisture % in wood to turn without worrying about cracking and warping? 6 to 8% ?????

In Canberra, yes probably, but it won't stop warping/cracking from inbuilt stresses being released as you turn that some woods/pieces are prone to.

[cava]

I am just learning to turn at the local woodworking club, and yesterday tried to turn some Cypress Pine that I have had for circa 6 years in the shed.

It was a piece 250mm x 80mm x 80mm unsealed with no cracks, and for all intents and purposes dry on the surface. However, when I tried to turn it, it was as wet as if I had just cut it down. Surprised me enormously. Not sure of the EMC, but would have to be >20%.

[Pat]

Cypress is known for doing this. I've turned "Dry" Cypress post and needed a raincoat.

If you are learning, 90*45 pine from bunnies, ripped to 45².

[cava]

If you are learning, 90*45 pine from bunnies, ripped to 45².
Thanks Pat, I have heaps of Radiata, but thought that I would try something a bit more challenging - the knots are interesting.:rolleyes:

[Christos]

When it comes to wood turning and the piece you are trying to turn is wet there are options that you can take. Turn and leave about 25mm thickness so you can turn it later when it does dry out, normally about 6 months. Another option is to turn to final shape with the wall thickness as thin as possible(3 - 4mm) and allow it to warp and maybe crack to give it a unique shape.

I have tried both options when I knew the wood was wet. I tend to do the following a large piece of about 250mm wide and over I tend to leave the thicker walls and with smaller pieces I try to turn down to thiner walls. It is interesting to watch what happens when you finish your part of the shape and the piece takes over.

[powderpost]

Another newbie question.......what's a reasonable moisture % in wood to turn without worrying about cracking and warping? 6 to 8% ?????

Timber will continue to move as the weather changes. It will adjust the moisture content according to the atmosphere the wood is in. On the coast at Cairns, the wood will expand in the wet season. The moisture content of the wood can be as high as 15%. On the tablelands where I live, that same piece will reduce it's moisture content to as low as 8%. Some timbers never fully "dry out". I have some white beech stumps here that are more than 30 years old and I will guarantee it will appear to be still"wet". Cypress pine is also a notorious timber.
In answer to your question, the figures you quoted, are fine for Canberra, but timber taken from Sydney to Canberra will shrink as it adjusts to the relative humidity in Canberra. Hope this helps you understand wood and it's idiosyncrasies.

Jim

[NeilS]

I just ran my moisture meter over my stach of pre-turned pieces and after a very long, dry and hot summer the moisture meter read between 0% and 3.5%.

By the end of our coming winter (our winters are wet) they will be up to about 4% to 6-8%.

By the end of next summer they will be back down 0% and 3.5%.

Some of those pre-turned bowls (and bowl like) pieces have been doing that cycle for the last 15 years. And it won't matter if they keep doing it for another 15 years. That is the advantage of pre-turning.

The other advantage of pre-turning is that you can do it immediately the tree hits the ground at 40% moisture content.

Yes, you get a spray pattern on your ceiling if it is as wet as that.

And, yes, you have to nurse them along after turning them wet/green. There are threads on this forum on the various methods that turners have used to do that.

And, yes, you do get a % failure rate, but they are only costing you your time, effort and maybe a bit of chainsaw fuel.

On the other hand, in my experience, you get an extremely high failure rate (ie checking) in wood that has been cut green and allowed to season in billots without pre-turning.

And, yes, you can always buy pre-seasoned blanks. Excusable for anyone who is making a living out of their woodturning, but there are few among us who fit into that category. Perhaps, also, if you are taking your first class or venture in woodturning.

For me, there is is a lot of satisfaction in taking the wood from a freshly cut tree to a finished piece, ie besides saving a bit of money. In the many thousands of pieces of wood I have turned I have only purchased two pre-seasoned blanks and they are still sitting on the shelf, somewhere!

I have also been the recipient of a few gifts of pre-seasoned blanks, but their value is in who they came from rather the blank itself, although some of those have been very special pieces of wood.

Once pre-turned, there is no rush to complete a piece and the more pre-turned pieces you have in your stach the more that is the case.

I should admit that occasionally I come by some very old seasoned red gum fence posts (and the like) and I never say no to those, but they are rare and not a source to depended upon.

In my experience, pre-turning freshly cut wood has many advantages. But, your experience (and that of other turners) may be different.

[dai sensei]

I just ran my moisture meter over my stach of pre-turned pieces and after a very long, dry and hot summer the moisture meter read between 0% and 3.5%.

By the end of our coming winter (our winters are wet) they will be up to about 4% to 6-8%.

By the end of next summer they will be back down 0% and 3.5%.

....

Even the best moisture meters cannot read below 5%, so I wouldn't rely on those readings

[NeilS]

Even the best moisture meters cannot read below 5%, so I wouldn't rely on those readings

Agreed, I just treat any readings as a relative measures, which is fine for my purposes.

Before economical moisture meters became available I weighed and recorded the loss of moisture, but that is more time consuming (and tedious) and didn't tell anything more that I needed to know. Anything that reads 8% or less on my meter is usually as seasoned as I need it to be for what I do (ie mainly turning bowls and platters). If the actual moisture content is different it doesn't matter as long as it behaves after final turning.

Having said that, I have noticed that my particular moisture meter never gives a reading below 3.5%, other than 0%. So, I know it is not telling me anything other than a piece of wood that is reading 0% is dryer (by some a mount) than a piece reading 3.5% and that is dyer (by some amount) than a piece reading 6% and that of a piece at 8%, and that of a piece at 12%, etc.

I know from checking my meter against some others that there was no precise calibration or accuracy in % readings between them.

I also know that the atmospheric moisture reading (humidity) on my inside/outside thermometer doesn't relate in any meaningful way to the readings I get with the moisture readings in my wood stach. I can have humidity (absolute, relative or specific) of say 60% for month after month, yet wood pre-turned at 40% on the moisture meter will start to lose and not gain on the moisture meter. They are reading different things.

Anyway, none of the that matters for me. All I'm interested in knowing is whether the wood is getting dryer. Although, I do have some indicative moisture percentages (according to my meter) to help me with managing the seasoning process. For example, when to remove from shavings or when to stack on open shelving. Those are based on experience of what has worked and what didn't.

However, it is worth mentioning that moisture meters don't tell you anything about the high oil/resinous content in some woods and they are the ones that seem to take forever to season sufficiently to avoid warping/cracking and are often the most troublesome. Moisture meters are reading conductivity through the water content in the wood and not the oil/resin content, which is far less conductive.

The timber industry use correction tables for the different species of wood, but that is getting a bit unnecessarily complicated, IMO, for a simple judgement that a piece of seasoning wood is ready to turn. I find if I don't get it quite right with the first piece I re-turn, I just wait a bit longer before turning the next lot of pre-turned pieces from the same batch of wood. There is always (or, if you are just starting out, there will eventually be) more pieces that are ready to turn in your growing stach of pre-turned pieces.

If you are a laminator/segmented turner your requirements may be different. Lidded pieces may also need more attention.

Sorry about the long post. Much longer than it needed to be!

[NeilS]

The timber industry use correction tables for the different species of wood, but that is getting a bit unnecessarily complicated, IMO, for a simple judgement that a piece of seasoning wood is ready to turn.

Here is an example of corrections for several wood species, including corrections for Silky Oak and Robusta Gum, which have very different corrections when approaching the 20% moisture content range. See page 14.

https://www.fpl.fs.fed.us/documnts/fplrn/fplrn061.pdf

But, as I said above, I don't bother. As you can see, the corrections are minimal down in the sub 10% range where we aim to get to.