Steam Bending Ancient Kauri

[Seth Peacock]

Hello all! I am new to this forum. I have some experience as an amateur luthier and a friend of mine is looking to have me bend a set of kauri for him. Unfortunately it seems that it is particularly hard to bend and little is said about it online. Can anyone Shes any light on how to bend this? I have a silicone blanket and homemade bending machine. I normally spritz with water, wrap in blank newspaper and aluminum foil. I’ve heard of a product called super soft sold on the stewmac website. I’ve never tried it but assume it might help. Any thoughts and advice would be appreciated!

Thanks

[Bill Raymond]

You might consider using original Windex with ammonia instead of water. Ammonia will act to soften the lignin bonds during bending but fully evaporate as it dries and cools.

[Barry Daniels]

I use Super Soft II on all sides and bindings that go in my bender. Probably unnecessary on the easier bending woods but it doesn’t hurt the wood so a lil extra insurance is a good thing, right?

[Bryan Bear]

I'm with Barry, I use Super Soft II on anything I have even the lest bit of reservation about. Cheap insurance and I'm pretty sure it is magic.

The process I learned for using SSII is to spray the sided liberally on both sides then prop them up over night to let it soak in. You should bend your sides between 12 and 24 hours after spraying. If you don't let it soak in enough it isn't as helpful (it is designed for veneer thicknesses and the instructions reflect that), if you wait too long it will have dried out of the wood and not be effective.

[Seth Peacock]

Thank you for the thoughts on the SSII. Do you wet it with water at all just before bending or is it enough with the SSII that has soaked in?

[Carl Dickinson]

I use a layer of brown wrapping paper on either side of the side. These are run through a water bath previous to laying up the bending sandwich. That provides the steam for the bend. I think it would work better than newspaper since it's thicker. I now also use Windex as Bill mentioned but have used SSII in the past. You could also lightly spray the side w/water just before bending.

[Randy Roberts]

A few cautions are in order before your friend uses this wood for a guitar...

Obviously every board will be different, but any wood that has spent millenia (in my case 44,274yrs +/- 418 yrs) in a peat bog is going to have it's molecular make up altered. Don't expect it to have characteristics of normal wood.

In my case:
It resawed as easy as balsawood, bent easily with no springback (so would appear that it's lignin was little changed ?), but was on it's own merits totally unsuitable for a back and sides. It's structural integrity was similar to crosscut balsa or cedar, with very little strain breaking off pieces, resulting in little structural integrity (degradation of cellulose?). This can be remedied by laminating both back and sides to another wood (in my case Osage Orange). Even then I wouldn't dream of it on a working, on the road guitar. A cared for, gently treated guitar sure.

It dented easily and deeply. Debris on a soft towel would scratch it, so hit any surface with shellac to protect it while building.

CA on ANY surface, not just end grain, wicks and discolors for up to 2 inches from where it is applied unless sealed first with shellac. At guitar thicknesses the thin epoxies can wick clear through to the surface.

It needs to be sanded way past normal grits to adequately bring out it's figure and chatoyance.

Besides the novelty of great age, the main attraction of the Kauri, it's incredible chatoyance and (rarely) whitebait, more than koa or Aust. blackwood, dulled or disappeared under epoxy, CA, and several water based poly's. I found that french polished shellac after sanding up through Micro-Mesh 4000 grit worked very well.

Back in 2009 Tim Mullins in Quebec posted the following on another forum:

While I was living in New Zealand, I worked pretty hard to develop a relationship with the Ancient Kauri Kingdom, which is the likely source of your material. I was able to get some material selected by their artist-in-residence -- an example of the "white bait swimming in waves" figure. I've made one guitar from it and have enough in stock for two more from the same billet. Have a look at http://www.mullinguitars.com/ancient-ka ... -0711.html

Bear in mind there is much variation from piece-to-piece, so your mileage may vary. There is no way that my stock is suitable for tops -- it is not at all stiff and the figure is partially due to the alternating areas of runout. While it is not petrified, at 30-45,000 years buried in swampland, it long ago stopped behaving like wood. From my experience:
- not at all stiff, so make some allowance for thickness
- bends super easy with no spring back
- marks very easily and these telegraph deep into the wood, whether it be bandsaw marks, accidental scrapes, or sanding scratches
- CA will wick through a plate thickness and cause staining on both sides (why I don't have enough in stock for a 4th). Don't bring CA near any surface unless you seal with shellac
- ditto for epoxy
- doesn't like edge tools and tends to behave like MDF.
- machines well
- sanding should go to much higher grits 600+ (Attached picture is of an unfinished back plate)
- seal with shellac to protect while building
- known for the chatoyance of its figure, especially under lacquer


Not to be too discouraging, with care it can be made to work.

[Seth Peacock]

Yes, thank you very much for the feedback. I appreciate the tips and warnings. I'll definitely bring that to his attention and do some strength/stiffness/other tests on scrap pieces before moving forward. What thickness did you bend and finish the sides at?

[Randy Roberts]

Seth,
Don't have my notes at hand, but probably sides were .075 - .085" Osage Orange with around .075" ( and probably around .060 -.050" once sanded down through all the micro mesh grits) of Kauri veneered onto it (I think I had absorbed Trevor Gore's thinking as to mass related to guitar sides by that point in time).
Again, every board is going to have it's own charateristics, but from my minimal experience with kauri, it's hard for me to conceive of it being structurally up to the task of being back and sides on it's own.
Even as eye candy veneered onto another, structurally apropriate wood, you are still faced with a surface wood that is soft and dents and scratches easily, and so are ending up with a problem similar, but even more vulnerable, to a cedar top...only now all over the entire body. I would recommend your friend think hard about how he plans to use the guitar, prior to commiting the board he has to this use. For some reason it brings to mind an image of me signing up my nine year old grandson to play for Edmundton in the NHL and thinking "It'll probably work out OK".

Don't get me wrong. The kauri guitar I made is easily the prettiest as well as the best sounding guitar I've made. But the sound owes nothing to the kauri - it's pretty, but fragile, bling. The Osage? - perhaps.

[Matthew Lau]

Man, thanks for starting this thread!