Saving Bark on Ponderousa Pine?

[Lloyd DeKay]

How do I? A wildfire recently burned through the grounds of the Columbia Gorge Discovery Center that only scorched a part of the Center but burned through the native plants on the property. They had to cut down some Ponderosa pines and I took a couple of 4' long by 8" diameter pieces that I thought I might be able to turn as natural edge bowls to donate back for their upcoming fundraiser. So far the bark spalls off as I'm turning, even though I tried to stabilize with a coat of polyurethane.
Does anyone have any ideas for how I can stabilize the bark before I turn the pieces so it doesn't spall off? If it's not possible to stabilize the charred bark I'll try singeing with a torch to al least give the idea of a burned exterior, but I'd really like to keep the natural blackened bark.

 

[Kent Reisdorph]

How do I? A wildfire recently burned through the grounds of the Columbia Gorge Discovery Center that only scorched a part of the Center but burned through the native plants on the property. They had to cut down some Ponderosa pines and I took a couple of 4' long by 8" diameter pieces that I thought I might be able to turn as natural edge bowls to donate back for their upcoming fundraiser. So far the bark spalls off as I'm turning, even though I tried to stabilize with a coat of polyurethane.
Does anyone have any ideas for how I can stabilize the bark before I turn the pieces so it doesn't spall off? If it's not possible to stabilize the charred bark I'll try singeing with a torch to al least give the idea of a burned exterior, but I'd really like to keep the natural blackened bark.

I believe most folks would use thin CA to ensure the bark stays put.

 

[Lloyd DeKay]

I believe most folks would use thin CA to ensure the bark stays put.

Thanks for the reply Kent - but I don't see how I could do that without bathing the entire half-round in CA. That would require at least a 1 gallon vat of CA that would have to be used quickly before it all hardened. Maybe you're thinking of some other way of applying the CA?
I thought a coat of polyurethane would do something like that but it doesn't penetrate the bark to bond it to the cambium layer. Maybe thinning the poly would help it penetrate better.

 

[Kent Reisdorph]

Thanks for the reply Kent - but I don't see how I could do that without bathing the entire half-round in CA. That would require at least a 1 gallon vat of CA that would have to be used quickly before it all hardened. Maybe you're thinking of some other way of applying the CA?
I thought a coat of polyurethane would do something like that but it doesn't penetrate the bark to bond it to the cambium layer. Maybe thinning the poly would help it penetrate better.

What I do is rough in the bowl to about 80% of the final wall thickness. Then apply the CA. If you lose a bunch of bark roughing it in, it wasn't going to stay on anyway. My experience with NE bowls is strictly hardwoods. I don't know if the pine will be different.

 

[Gerald Lawrence]

I do not think you will be able to save bark on pine that has been in a fire. However Like Ken told you I turn outside and put CA on the edge then cut the inside with a parting tool and put CA there also. No guarantees with NE and for most will eventually come off. Another tip is you can pick up bark from shop floor and glue into those voids.

 

[hockenbery]

Maybe you're thinking of some other way of applying the CA?

On fragile bark you need to avoid making the normal push cut foot to rim on the outside.
I’d suggest using an Ellsworth type grind or a Michelson grind and a pull cut on the outside.

1. I find on most bowls a pull cut foot to rim will cut the bark rather that pop it off.
2. A push cut rim to foot is even more likely to cut the bark cleanly - it requires being able to control the gouge through the interrupted cut to get a nice curve while minimizing the tearout from cutting the wrong way.
I would expect the pine to tear more that most woods from the wrong direction cut.

Once I get a rim cut I run thin CA all around where the bark meets the wood
Make a finishing cut, more CA.

I think you will have the most success with the pull cut. Light cuts, sharp tool, high shear angle
On each bowl you hope for the bark to cut cleanly. If it pops off then take it all off. Color the rim or use the torch to get the effect.
Without the bark the bowls are functional too.


Here is a Demo I did for the Sarasota Woodturners using a live oak blank that was past its prime. Bark was just about to fall off but it stayed with a pull cut. (They gave me a bonus R in my name)

View: https://www.youtube.com/watch?v=A6XccQl_0BY

 

[John K Jordan]

The bark on this looks sturdy but immediately warned me it would gladly abandon the bowl in big chunks.

I first cut the blank round on the bandsaw so I could begin the shaping gently, no aggressive cuts. Turned the outside first, as usual, starting at the rim.
Applied CA then started shaping outside the rim from the rim down. As working towards the final shape, soaked the bark and boundary with thin CA, often.

When starting on the inside, first applied glue more CA to the outside of the bark, made gentle, careful cuts down through the bark near the rim.
Stopped each cut and applied more glue to the bark and boundary. Continued to apply CA when approaching the final rim thickness. Finished the outside shape, then the inside, carefully staying away from the bark. Sanding by hand only.

This is small, maybe 6" across. Warped nicely. A suitably interesting amount of the bark stayed on.


JKJ