Bowl Split

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Bowl Split

Postby pete Kafno » Thu Dec 13, 2007 12:39 pm

Hi there
This is really a question for Robin Wood but any answers would be gratefuly accepted.
The Warwickshire group met last week and Trevor very kindly came down and brought his tools and his knowledge.
He supervised a new recruit making a cherry bowl and with a lot of assistance it was finished that afternoon.it was turned from quite fresh cherry wood and came out beautifuly.
It had a small split which apparently dissapeared after a few days and the application of some veg oil.
However when it was used the following weekend the split reappeared spilling hot soup into said recruits lap.
Do you have any suggestions as to an enviromentaly friendly, filler/glue that might solve the problem.
I wondered if beeswax might be worth a go but am not sure if it might melt with hot liquids.
I do not want to use a chemical glue.
I am aware of your observations ref cherry in your bowl book.
Any help would be much appreciated.
Thank you
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Postby robin wood » Thu Dec 13, 2007 1:05 pm

Hi Peter, thanks for posting the question here...means others can contribute and everyone can see the answers.

First why did the bowl split in the first place lets try to avoid it happening again because a split and repaired bowl will never be as good as one that never split.

Most bowls that split do so for one or two reasons. Most common is that there is some of the pith or central growth rings in the bowl...its always best after splitting a log in half to cut away some of the flat surface to get rid of the central growth rings this reduces stress in the finished bowl. Another common error is to use wood which already has a tiny incipient crack in it which opens up as the bowl starts to dry. When selecting wood to turn look very carefully at the end of your log to see if it has small splits in it. You need to cut off and discard anything from 2"-6" to get rid of every trace of these cracks before cutting your blank. Finally it may be that you did all these things and it cracked anyway that happens to me very occasionally maybe 1-2 in 100 but with cherry it rises to maybe 5-10 in 100 so I don't use it any more.

So now to damage limitation what to do with your cracked bowl. If you want a quick modern fix try this...first get the split to close up..this may mean popping it in some water for a few hours or even overnight. When its closed up run some superglue into the crack, I get a cheap generic thin superglue from any of the woodworking shops eg craft supplies. It may open up again in the future but its quick and easy and often works surprisingly well.

If you want a period style fix drill some holes either side fo the crack with your smallest bit, and stitch it together with copper wire stripped out from electrical flex.
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Postby Trevor Watson » Sat Dec 15, 2007 1:45 pm

The crack was in the end of the log and only became apparent during turning. I'd be interested to hear how well the superglue fix works, if that is the chosen repair.
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Postby paul atkin » Tue Apr 15, 2008 2:30 pm

Image what is it with cherry wood, i was proud of this lovely bowl, nearly 9inch across, i turned it green and left it in a box of wet shavings for about 10 weeks, yet still it cracked :roll: oh well it will do for fruit :D
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Problems with cherry

Postby Robin Fawcett » Tue Apr 15, 2008 5:29 pm

That's a crap photo by the way Paul!

What it is with cherry is the sapwood. Its full of moisture and shrinks much more and faster than the heartwood. I get it in some of the things I spindle turn.

Cherry also moves about a lot as it seasons. I ripped a fairly big butt into planks with the chainsaw a couple of years ago with the idea of using them for bench and stool tops. They warped so much they now look like propellers!

None of this stops me using it if it comes my way though as it's such a lovely wood.
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Postby robin wood » Thu Apr 17, 2008 3:07 pm

paul atkin wrote: what is it with cherry wood, i was proud of this lovely bowl, nearly 9inch across, i turned it green and left it in a box of wet shavings for about 10 weeks, yet still it cracked :roll: oh well it will do for fruit :D


Yep been there, done that, I don't use cherry for bowls any more. :D Its a shame because I love the movement but not if too high a proportion split.
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Postby paul atkin » Thu Apr 17, 2008 5:31 pm

sorry about the dodgy photo, my camera bust and i used my phone instead :roll: the other half of the cherry log did the same thing, i certainly wont waste the effort trying again, on a plus side of things i do have two very nice fruiit bowls even if they are cracked :D
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Re: Bowl Split

Postby Bertie » Tue Apr 21, 2009 10:36 am

Hope you dont mind a little posting from a stranger -
This is my experience - wood cracks along its length due to a differential in drying - take the differential away then you limit the cracks - plastic bags are best.
I usualy leave the bowl out for a few hours then bag it for a couple of days, then out for a few hours, then bag it again. Over about 5 weeks lengthening the exposure it gets untill you can leave it out permanently.
The thicker the bowl, the longer you need to bag it. The thinner the less likely it is to crack.
There are two types of cherry - the wild and the cultivated.
The wild grows to a considerable size and is a very kind tree in every way, carves and turns a treat.(gean)
The garden is very interesting but the wood is hard and difficult to dry.
Some woods like oak are extremly difficult to dry even in a kiln - my losses have been up to 100% - untill i turned it thin, even then it needed care.
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Re: Bowl Split

Postby woodness sake » Tue Apr 21, 2009 1:40 pm

In some cases, the transition from a high humidity environment such as most spring pole work/storage areas to a cozy, warmed interior living space will cause a piece to be dried out rather quickly, thus causing a sudden change in the shape and internal stresses in the wood. Or,if you are patient, the change of seasons (especially from summer to winter) will have a slower but equally undesirable effect. I offer a 4 season "warranty", but, it be wood. :roll:
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Re: Bowl Split

Postby Andy Coates » Tue Apr 21, 2009 10:44 pm

I have to agree...cherry is a very naughty wood when turned green. And can be just as naughty when seasoned (in bowl blank form rather than thin planks). But it's so pretty I can't resist turning it green or otherwise. (Although my wild plum bowl did cause a major upset recently!)

Paul...I love the bowl you turned...it's a lovely bowl any wood lover would be proud to own. The resulting shape is pleasing to the eye, and seems to be uniform in its distortion, which I'd guess is because you cut the blank carefully with equal (naughty) sapwood either side, and for the same length down the log. I should add that I sell a lot of distorted bowls...and intentionally too!

I also use Bertie's bag & breath technique to good results...except with Holly which clearly has something against me personally.

Another trick, which may be abhorrant to some here, is to coat the end grain with neat PVA when it comes off the lathe. Allow to dry and then place the bowl in plastic bag with a handful of the damp shavings you produced in making it. After this treat as per Berties method. The idea being that the PVA reduces moisture loss via the end grain, balancing out the overall moisture loss rate across the bowl. Success rates are very good indeed.

But if all your cherry bowls end up looking like the one you posted I wouldn't bother...it's a gem.
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Re: Bowl Split

Postby paul atkin » Tue Apr 21, 2009 11:49 pm

andy i have a house full of gems :D my wife says how come i end up with all the rejects, i say youve got the best ones :D wood needs character :D a crack to me is a breathing hole, you cant store liquid in it, but i aint ever seen an apple fall through a crack :D and yep my distorted stuff sells very well too :D half logs turned green, but cherry i dont know i am running out of space in the house, maybe if i called them ART :D
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Re: Bowl Split

Postby paul atkin » Thu Apr 23, 2009 1:32 pm

here you go andy i have a matching pair 8)
a pair of cherry bowls.JPG
a pair of cherry bowls.JPG (105.79 KiB) Viewed 10166 times

When it comes to preparing my blanks i am far from precise,i just cut off a length of log and crack it down the middle :D I turn past the first couple of growth rings and see how it ends up. My workshop is very cool and airey and have no problems with any of the other woods i turn, i just sling them on a rack and leave for a few weeks, cherry pah i lovingly buried it in a box of wet shavings watered it each day, they even spent some time in my beer fridge :D but yet they betrayed me and cracked, as a saleable bowl they are worthless to me they are priceless and are used every day :D
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Re: Bowl Split

Postby gavin » Thu Apr 23, 2009 3:51 pm

paul atkin wrote:i just cut off a length of log and crack it down the middle

You could also try splitting out the "pith plank" as in this thread :-
viewtopic.php?f=14&t=745
i.e. two splits and not one
There may be energy saved by splitting out the pith plank, and so avoiding turning away the top half inch or so of your bowl. And your single split method works pretty good too.
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Re: Bowl Split

Postby Andy Coates » Thu Apr 23, 2009 5:15 pm

Not a phrase I ever thought I'd utter to a Bodger...but, nice pair Paul!

And Gavin's suggestion has great merit. Even for power turners. Far too many split straight through the pith, and rarely take the next inch of flat away which removes a lot of the stressy wood from around the pith. I think they view it as "wasting wood". Far more bowls would survive if they wasted wood at the blank prep stage.
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Re: Bowl Split

Postby paul atkin » Thu Apr 23, 2009 6:45 pm

thet didnt crack how i expected.
cracked bowls.JPG
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