Warping bowls

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Warping bowls

Postby Stanleythecat » Tue Oct 04, 2011 10:13 am

I have just been reading how some 'machine' lathe turners use all sorts of methods to try to season and stabilise greenwood for turning. Two methods 'soap soaking' or 'alcohol soaking' both rewarded the turner with uncracking and unwarping bowls at a very high success rate. But obviously employ chemicals to help which is not why I set my self up to turn in the wood!

However as part of the same process there was one trick they did use that was of interest to me was that they wrapped the outside of the finished bowl with craft paper; leaving the centre exposed. The bowl was then left in warm room upside down on a drying rack. This allowed the bowl to be seasoned in a matter of days.

The thinking is that if a bowl dries from the inside out the tendancy is for the bowl to pull itself inwards and not crack; the inside surface shrinks and pulls it all together. (The opposite being that the outside dries more quickly and shrinks, therefore pulling the bowl apart and thus causing it to crack)

Not that I have turned a great deal of bowls but we work a lot with groups of people, some of which have the opportunity to turn a bowl for themselves. However it is often the case that these people don't have the space to season their bowls properly at home and it would be nice to find a way that would help them have a successful experience.

(For reference this was read from a link in Paleoplanet)

I will no doubt be checking this out to see if it works shortly!
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Re: Warping bowls

Postby gavin » Tue Oct 04, 2011 1:03 pm

Stanleythecat wrote:... we work a lot with groups of people, some of which have the opportunity to turn a bowl for themselves. However it is often the case that these people don't have the space at home to season their bowls properly at home

I am v surprised to read this. How much space do you need to season a bowl??
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Re: Warping bowls

Postby robin wood » Tue Oct 04, 2011 2:36 pm

Power turners devise all manner of weird ways of seasoning bowls to make up for their lack of knowledge. If you cut the blank from the tree correctly in the first place you can forget all that hassle and drying it becomes straightforward.
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Re: Warping bowls

Postby Stanleythecat » Tue Oct 04, 2011 3:01 pm

Don't be surprised Gavin!

Some people fall on hard times and find themselves living in a small flat with no garden etc; surely not the best place to season a green bowl?

To clarify we work with people with mental health issues; they come to our sites where we are embracing the challenge of learning traditional woodland crafts. The confidence building and therapeutic value of practising traditional crafts in a stable and safe environment are immeasurable.

The bowl they have made then is a major achievement quite often in fitness alone! To hold something functional after all that effort is a real achievement; to be reminded of that achievement every time you see your work is even more important.

As the sites we use are open to the public we can't store anything so bits have to be taken home, wherever that might be.

Any suggestions would be very welcome.

Leo
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Re: Warping bowls

Postby Stanleythecat » Tue Oct 04, 2011 3:09 pm

robin wood wrote:Power turners devise all manner of weird ways of seasoning bowls to make up for their lack of knowledge. If you cut the blank from the tree correctly in the first place you can forget all that hassle and drying it becomes straightforward.


Well I'd happily put my hand up and say that I too have a lack of knowledge but I'm trying to remedy that... it takes time! Much of what I have picked up is thanks to the helpful advice of this forum.

We remove the central rings and try a variety of greenwood under 12 months felled, but surely the average home is not the place to season your bowl? (i.e. from a moist woodland to a warm dry house)

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Re: Warping bowls

Postby gavin » Tue Oct 04, 2011 8:56 pm

Stanleythecat wrote:...but surely the average home is not the place to season your bowl? (i.e. from a moist woodland to a warm dry house)...

Try it.
I think you will find it works fine. Hence my surprise - if folk sleep in a bed, they could season their bowl under the bed.
If your bowl walls are not too thick, you will reduce the risk of splitting. Some species e.g. cherry are more prone to split. Since you are removing the pith ( and I gather turning side-grain) you have removed one of the most common splitting start points.
Weighing it on electronic scales is instructive - you can see the rate of moisture loss until it reaches Equilibrium Moisture Content or EMC.
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Re: Warping bowls

Postby Bob_Fleet » Tue Oct 04, 2011 9:52 pm

You'll see from other postings just how dry it eventually becomes.
You start with fresh green wood
the first stage is probably air dried outside
next inside a shed or workshop
then inside a house
then into the centrally heated living room.
At all of these stages the wood is 'moving'.

Some of the skill is to predict how it will move so you prepare for it right at the beginning.
Otherwise you might be left trying to 'correct' movement after you've made something by putting it back on the lathe once dried - power turners usually do that to dry the wood quicker.

Oh the fun of playing with greenwood.
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Re: Warping bowls

Postby grinagog » Wed Oct 05, 2011 8:39 am

Hi Leo

There is also a nice way to avoid "some" stress when drying a bowl and that is a way that I saw in Robin Woods book.

To cut three blanks out of one log keeping the foot (or bottom of the bowl blank!) towards the heart of the wood!
Ive only done it with two logs (hence 6 bowls in all!) The first log I used a chainsaw and the second I tried to split with wedges( but found it very hard to do!)
I would love more tuitiion and practice for the second method(if anyone knows more?)

I found it less likley to split as most of the stress of drying is in the foot of the bowl and not the rim!

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Re: Warping bowls

Postby Stanleythecat » Wed Oct 05, 2011 9:15 am

Hi Nick

I was just researching beecause as you know most of the people we work with don't have shed's or gardens etc and the bowl literally comes off the lathe and has to go home with them. It was a chain of thought that I picked up on Paleoplanet. Not the 'traditional' way but central heating or space were perhaps never really an issue for the traditional craftsman.

I remember you metioning the 'inside outer' method; again its down to the availability of the right size of material etc so up to us to plan for it!

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Re: Warping bowls

Postby Ian S » Wed Oct 05, 2011 7:29 pm

No guarantees of success, but you could try drying in a plastic bag. This is the way I dry carved bowls because I live in a flat in the middle of a city and don't have the luxury of a garage, shed or whatever.

Put the bowl in a plastic bag and wrap the bag round and over the bowl, more or less sealing the bag.

Each day for the first week, take the bowl out of the bag, turn the bag inside out (so wet surface outside, dry surface inside) and put the bowl back in the bag.

For the second week, leave the bowl out of the bag for about an hour a day, again turning the bag inside out daily.

For the third week, leave the bowl out of the bag for 2 or 3 hours a day, again turning the bag inside out daily.

You'll get an idea how much water the wood holds by how much water collects on the bag.

Try and use the coolest room in the house, and keep out of direct sunlight.

The bag stops the wood from drying too quickly, but the turning and airing will hopefully prevent mould.

Good luck!
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Re: Warping bowls

Postby Windsorman » Thu Nov 10, 2011 11:38 am

robin wood wrote:Power turners devise all manner of weird ways of seasoning bowls to make up for their lack of knowledge. If you cut the blank from the tree correctly in the first place you can forget all that hassle and drying it becomes straightforward.


Just what I was thinking when I read the title. I think the biggest issue here is proper "blank" selection. Work with the wood and the grain and there won't be any problem. Dry them slowly in any way you wish. They should be fine!
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Re: Warping bowls

Postby Stanleythecat » Fri Nov 11, 2011 2:08 pm

Windsorman wrote:
robin wood wrote:Power turners devise all manner of weird ways of seasoning bowls to make up for their lack of knowledge. If you cut the blank from the tree correctly in the first place you can forget all that hassle and drying it becomes straightforward.


Just what I was thinking when I read the title. I think the biggest issue here is proper "blank" selection. Work with the wood and the grain and there won't be any problem. Dry them slowly in any way you wish. They should be fine!



Ah but there in lies the problem! For those of us without the essential knowledge it is a few years of continuous trial and error to work out the 'ins' and 'outs' of bowl seclection. The beauty of this forum is the ability to ask!
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Re: Warping bowls

Postby Brigstock Bodger57 » Wed Nov 30, 2011 8:36 pm

I followed a professional power lathe turners advice about drying bowls when he saw me turning one at a show in the early 90's. He told me that for small bowls he put them in the microwave on medium power for bursts of 1 minute. I tried this out and it did work, with none splitting but some warping. This was fine until I answered the phone with a bowl put back in for just another minute. Luckily I smelt the smoke and got back in time to get the bowl, which was now on fire, out and into the sink where I could put it out. I decided after that to let them dry in their own time and not try to hurry them.
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Re: Warping bowls

Postby robin wood » Thu Dec 01, 2011 1:29 am

Stanleythecat wrote:Ah but there in lies the problem! For those of us without the essential knowledge it is a few years of continuous trial and error to work out the 'ins' and 'outs' of bowl seclection. The beauty of this forum is the ability to ask!


Yep and the important thing is to ask the right question. What I was trying to say was by concentrating on drying methods you are asking the wrong question, start asking about how to convert the blank, concentrate on that. It is simple and the answers are already here it needn't take years of trial and error though that is how it had to be for me. I can and do turn bowls and bring them straight into a warm dry house.
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