Nortfolk island pine bowls

[Don Hiatt]

I have been turning Northfolk island pine bowls (end grain ) range up to 14” dia three in . Deep ,wall thickness 3/16 to 1/4 and I find that some have cracker along grain lines and was wondering if I used the wood Gardner polycrystalline if make the wood more durable , or is there some way to help this condition,have been doing the blo and mineral spirits soak before final turning
Thanks for helpful thoughts

 

[Richard Coers]

No idea what "wood Gardner polycrystalline" is, so can't help with that. I offer my opinion, but I have no idea of your turning skill level or what tools you are using. You really aren't to extreme thin turning with 3/16 to 1/4 wall thickness, but it requires and extremely sharp bowl gouge and light cuts to do it. You need to steady the final cuts with your free hand supporting your stock. My guess is that you are getting a resonance in the wood while cutting and that is what is cracking the bowl. Either that, or you let it sit on the lathe overnight or while taking a break and then it cracks.

 

[Bill Boehme]

I would suggest that you start a conversation with forum member @Dan Stevenson . He turns a lot of NIP.

 

[Emiliano Achaval]

I have been turning Northfolk island pine bowls (end grain ) range up to 14” dia three in . Deep ,wall thickness 3/16 to 1/4 and I find that some have cracker along grain lines and was wondering if I used the wood Gardner polycrystalline if make the wood more durable , or is there some way to help this condition,have been doing the blo and mineral spirits soak before final turning
Thanks for helpful thoughts

We do not soak the Cook Pine or NIP before final turning. We do it after you are done turning and sanding. My good friend Ron Kent wrote several articles about his process, he has some of it on his web site. I believe his family is still maintaining the site, Ron sadly left us for a better place in heaven. You can also cut one tree on Monday and have a bowl ready to sell by Sunday. or, you can double turn, let it dry a few months and finish it. Ron did both. Both species are some of the most stable wood I have ever worked, especially on the end grain, never had one crack. I had blown many trying to go thin for the translucency. If you haven't blown many, you are not trying hard enough, I was told by Ron a few years back when I interviewed him for an article for Woodturning UK magazine.

 

[Dan Stevenson]

Happy to share what I've learned so far on NIP.
I turn two kinds of NIP, processed thin and soaked many times for translucency and natural/very lightly quick dipped in the soak and wiped in. I tend to do lots of work featuring the knots and find they need lots of management (CA glue help) as the densities of knots, the heart and sapwoods are different and dry at different rates. CA glue inhibits the oils from penetrating, polymerization and creating even coloring/contrast - so be careful where you use it on raw wood. I will sometimes start the soaking (2 or 3x) before I have a totally finished, sanded form if I want to colorize/contrast the wood and then start the CA knot management.
Cracking along the grain pattern may be ring shake and unfortunately I do find it showing up sometimes in my NIP logs. It certainly makes thin turning more difficult and at times a piece must be tossed if its really bad (and frankly dangerous to turn). CA and some neutral colored fine NIP dust can help fill it in and stabilize it a bit while you're working on it. BTW, I always turn green NIP wood - and I very rarely rough turn.