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Preventing cracking in new blanks

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Kerrowman

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I decided to have a binge on preparing some blanks for bowls and other creations by preparing about 12 items in one sitting, in part because the chainsaw sends chippings and dust everywhere and I only want to clean up once. The wood has been mostly cut down within the last few months.

I felt pleased with my efforts but then the next day remembered that I probably ought to stop any undesirable cracking by using some end seal. Indeed a couple of pieces already had 1cm deep cracks in one face.

As I don’t have a band saw I use a chainsaw to cut an octagon of sorts around my intended perimeter and where, in principle, just two of those faces will be end grain and the others side grain.

My query is should one coat all the surfaces or just the end grain ones?

If one covers it completely then that will surely prevent any further drying which will mean more to be done after the first turning - I use a microwave method.

Some pictures will clarify.

Thanks

Jules
 

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AdrianUK

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Hi Jules, I seal my blanks just end grain, get the odd one or two that still move but generally ok.
Agree that if you seal completely, leaves nowhere for moisture to leave.
 

okeydokey

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I suspect there are as many methods of end sealing timber as there of sharpening chisels, but I was accidently came across (the assertion) that emulsion paint 2 coats is pretty good and stops cracking/splits. What say ye?
 

foxy680

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It seems a balance needs to be struck. If I had a special piece of wood I would take the precaution of sealing all round (PVA glue is my go-to), and then be prepared to wait for the slower drying time. If I had plenty of the wood, and wasn't too bothered about some pieces showing some cracking, then just the end grain would suffice.

Any bowls blanks I've purchased from a retailer have always been sealed all the way round with wax (which suggests it's worthwhile, at the time is still worth the expense for a commercial enterprise).

Finally, surely, (happy to be corrected) once the log ends are cut to a curve, end grain is exposed all the way round?
 

Kerrowman

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Yes I’ve noticed that purchased blanks are sealed all round but then they have usually been kiln dried and so one doesn’t want them to loose any more moisture. (They are hard enough on ones tools I have found).

So I’m thinking that for green or nearly green that just end grain will even out the drying process a bit by sealing the Xylem vessels (my biology is a bit rusty) while still allowing them to gradually loose moisture as you want them to anyway - but hopefully in a more even way to minimise warping etc.

Well that’s my current thinking.
 

Owd Jockey

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I've found myself in a similar situation with some very large pieces of Black Pine i'm turning into platters (20" od). In the past I have sealed with melted down candle wax, which is a cheap especially if you collect all the wax that does not burn away. I've had mixed success with wax in the past. However, one of your pieces, the one with the crack, I doubt you could have done much about as there would have been tensions and forces built up around that crotch that wax or sealer would not have held.
I've cut most of my big pieces into large rounds/truckles, but in this heat we've had has produced many radial cracks from the pith (which is normal), i've arrested these with CA glue in the short term. I just need to finish rough turning them and get them into my wood kiln.
I did, as an experiment, wrap one of the rounds with cling-film. After 24 hours, you would not believe the amount of free water that had precipitated out from the wood and also mould had set in.
BTW, I have tried putting them in the brown paper with wood shavings and putting them away in the dark. Most of the pieces had developed cracks to some degree, so I don't do that anymore (out of sight out of mind etc). So now I keep a close eye open for my freshly cut / turned pieces and try and deal with the cracks before they become a big problem. But i'm still learning, hey arn't we all?
 
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KimG

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Although you do commit to a design, the best way to avoid excess cracking is to rough turn the blanks, say to a thickness of and inch or a bit more, this helps the wood to dry more evenly and warp instead of cracking. Doesn't work with every wood or piece but the majority will be fine. I rough mine out and leave them in the attic to dry, most are Ash or Sycamore, they seem to respond well to this process. I have also done the same with Holly, Laburnum, Oak and Hawthorne.
 

Kerrowman

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Lots of good ideas presented, thank you.

As I batch cut my logs I can’t rough turn them all in a short space of time so have sealed the end grain faces. Any more cracks I find when I come to turn an individual piece I will deal with at the time with CA or potentially making it a feature of the piece.

Yes, one of my pieces has a large crack but I’m hoping I can lathe down beyond it as it’s only about 1-2cm deep. Now that it has end seal on it that should minimise it cracking deeper.
 
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