Steaming ?

[whatknot]

Okay I tried to steam a childs chair back earlier

Not having a container large enough I used a large heavy duty plastic bag, sealed the steamer tube to it and folded the end over with spring clips, it steamed away happily for an hour like an inflated balloon

I whipped it straight out and onto my form, it was far from as flexible as I had hoped

I clamped and bent round the first half, but started to notice a split and try and I might I could not get it to complete the bend round the form, on finding the start of a second split I gave it best

The only thing that came to mind was that when I took it out of the bag after releasing the steam, I found a fair amount of water which the wood had been lying in, could that be the reason ?

ie would it be better to raise the wood so it was steamed rather than soaking in water

 

[Daniel2]

Hi,
I'm by no means an expert.
But, in my steaming box, the workpiece is held up out of the trickling condensation by a series of wooden dowels.
The wood comes out very pliable.
It doesn't sound good, to have the work sitting in water; possibly even has a cooling effect ... ?
I'm sure someone who knows more what they are doing will be along shortly.


ATB,
Daniel

 

[whatknot]

Hi,
I'm by no means an expert.
But, in my steaming box, the workpiece is held up out of the trickling condensation by a series of wooden dowels.
The wood comes out very pliable.
It doesn't sound good, to have the work sitting in water; possibly even has a cooling effect ... ?
I'm sure someone who knows more what they are doing will be along shortly.


ATB,
Daniel

Thank you Daniel

That was my thought also but sadly after the event when it was to late, it had not occurred to me whilst it sat there steaming for an hour, I think I will have to try it again supported

Thanks for your reply

 

[MikeG.]

No, that doesn't make any difference. You can actually boil wood in water to achieve bending in the same way as steaming. Steaming in a bag is standard boat-building stuff. You could try inserting a drain hose to take the condensate back out to the boiler, though, because if you have too much water it may not be quite hot enough, I guess.

Did you steam it for long enough? An hour an inch is the rule of thumb, but if you've got kiln dried wood you might need longer than that. The other big secret of steam bending is to keep the wood in compression if you can......ie don't let it get any longer. The brilliant Dave Engels, a wheelwright and coach-builder, has a steel strap and clamped end blocks for the big bends he does. You probably know all this anyway....and you know to have chosen the straightest grained wood you can find. Any flaws, or any grain that runs out to the edge of the wood, and you're almost certainly doomed to failure.

 

[Daniel2]

Very good point, about the boiling in water trick.
So, possibly it is the condensate getting too cool ?

 

[whatknot]

No, that doesn't make any difference. You can actually boil wood in water to achieve bending in the same way as steaming. Steaming in a bag is standard boat-building stuff. You could try inserting a drain hose to take the condensate back out to the boiler, though, because if you have too much water it may not be quite hot enough, I guess.

Did you steam it for long enough? An hour an inch is the rule of thumb, but if you've got kiln dried wood you might need longer than that. The other big secret of steam bending is to keep the wood in compression if you can......ie don't let it get any longer. The brilliant Dave Engels, a wheelwright and coach-builder, has a steel strap and clamped end blocks for the big bends he does. You probably know all this anyway....and you know to have chosen the straightest grained wood you can find. Any flaws, or any grain that runs out to the edge of the wood, and you're almost certainly doomed to failure.

This is the top rail of a small childs chair of at least 60+ years vintage and probably more

It was in a garage for some years and I presume the damp didn't help as the top rail tried to straighten itself and popped off one side

So this is my effort to re-bend it back to the shape it once was, after being stored inside in the dry for some 10+ years more

In my case the rail was lying in the water at the bottom of the bag, which would be quite cool once it condensed as it was on a flag floor, I simply had not given that part enough thought

So rather than being boiled for an hour its sat in some water while the top half steamed

I was lead to believe an hour would be sufficient but steaming rather than having a bath ;-)

I think I will raise the whole bag off the ground and insert a drain tube as well as raising the rail off the bottom

 

[Inspector]

Trying to rebend decades old chair parts back to their first steam bent curve is never going to be easy if even possible. Firstly it will take longer to get wet and hot enough to become pliable. You are not going to get as hot in a plastic bag as you would in a steam box. Loses heat too fast. You will still have failures because of any cracks etc that formed from it's life and the added stress points of the shaping and holes it got while being made into the chair part after the original steaming. As pointed out by MikeG not having bending straps for the bending. If I remember correctly theses are old children chairs that don't have a great monetary value. I applaud the desire for sentimental reasons to fix them but feel it would be better to make new parts by steaming green wood or laminating thin strips from dry.

Pete

 

[whatknot]

Trying to rebend decades old chair parts back to their first steam bent curve is never going to be easy if even possible. Firstly it will take longer to get wet and hot enough to become pliable. You are not going to get as hot in a plastic bag as you would in a steam box. Loses heat too fast. You will still have failures because of any cracks etc that formed from it's life and the added stress points of the shaping and holes it got while being made into the chair part after the original steaming. As pointed out by MikeG not having bending straps for the bending. If I remember correctly theses are old children chairs that don't have a great monetary value. I applaud the desire for sentimental reasons to fix them but feel it would be better to make new parts by steaming green wood or laminating thin strips from dry.

Pete

I thought it would be a possible non starter, but you don't know until you try do you

I did want to keep it as original as possible, partly as my own backside filled these chairs back in the day, as did my brother and sisters before me, they were a gift from my sister who was the last headmistress of this particular school, so they do hold a lot of sentimental memories

It will probably come to the point of making a new rail

Thanks for your input

 

[Inspector]

Depending where the bend relaxes, one spot for instance, You could cut that section out and splice in a sawn part. That would preserve more of the original wood.

Pete

 

[Daniel2]

Just out of curiosity, Whatknot, what part of Cornwall are you from.
I come from between Liskeard and Callington.

 

[whatknot]

Depending where the bend relaxes, one spot for instance, You could cut that section out and splice in a sawn part. That would preserve more of the original wood.

Pete

Thanks for that , I shall have to put it on hold as Thursdays the next day I will have time to look at it

I suspect I will end up making a new rail

 

[whatknot]

Just out of curiosity, Whatknot, what part of Cornwall are you from.
I come from between Liskeard and Callington.

I am over near Newquay, although I was born in Leicestershire and moved here in 1997