Drying Amboyna Burl

[Chairman]

I am a chairmaker in Sarasota, FL. I flew out to CA earlier this week and purchased a 900 pound Amboyna burl and then had it milled on a wood miser band saw to 8/4 slabs. The dimension of most of the slabs is about 34"x 24". I cut it across the pins to maximize the beauty of this rare and valuable wood. After cutting I reassembled the burl into a solid piece and have had it banded in preparation for shipment back to FL.

I am looking for a plan to safely dry this wood in the minimum amount of time. My plan right now for the near term is to put brown paper between the layers to wick away moisture for the first few weeks. The paper will be changed out daily. Immediately following that I plan on sticking it and putting the slabs in a low temperature dehumidified chamber I've built. My normal ambient humidity in my shop is between 60 and 80% moisture content. In my home built box with the dehumidifier on the ambient moisture is around 30% and the temp is about 110. I do not plan on putting sealers of any kind on the slabs. The bark is intact around all slab edges. I have three questions:
1.) Have I already made a mistake in my approach, ie is it too aggressive? If so what would you suggest as a better way of doing the initial drying of this burl?
2.) Once I remove the first two thirds of the moisture and get it down to about 20% what should I do next to get to harder moisture out? My goal is 7% with a minimum of checking and cracking. Obviously letting air dry for several years might be preferrable but this is a commission piece and I would really like to get it done in the next 6 months to a year max.
3.) Might vacuum drying be an answer and should I consider stabilization before doing anything else.

My website is www.parkerconverse.com for anyone who wants to look at my work. When finished this rocking chair will sell for $25,000. I am anxious to protect my clients substantial deposit which would include not turning the Amboyna to kindling in the drying process. Any advice or leads to more knowledgeable people would be greatly appreciated.
Thanks,
Parker

[old3dogg]

Vac dry it.

[Chairman]

Mr. Old Dogg:
Your response employs an enviable economy of words. You must understand, however, that my knowledge is that of a stump regarding the processing of wood. With the simple instruction to VAC dry I am likely to pull out the shop vac and give the slabs a good cleaning. Specifics would be helpful. What type of vacuum chamber, how long, what atmosphere, what temp? Probably more important would be a reference to a facility or person who provides vacuum drying services and preferrably has experience with valuable burls. Can you recommend anyone?

[crtreedude]

Nothing to add about how to get it done, but you do beautiful work. I would be afraid to sit in one though!

[old3dogg]

Den will be here in a day or two to tell you all about vac drying!!!!

It isnt "Mr. old3dogg". Its Mike.

I dont dry anymore. Gave it up for something better.

Hot water platen type vacuum dryers work the best.

[Tom]

Welcome to the Forum, Parker.

The moderator of this board Dennis Socling, is into vacuum kilns real heavy.  He designs and builds kilns and is an encylopedia of information.   His company website is at
http://www.pcspecialties.com/

Dennis has help guys design and build vacuum kilns and even helped a company in my hometown find a vacuum kiln operation that would get them over the hump till they could make a decision on buying a kiln.

If you need to contact him immediately, his website has a contact button.  He shows up here regulary though.

[Chairman]

Tom, Mike and the other gentleman:
Thanks for your feedback. Coincidentally I got in touch with Dennis's company today and spoke with his number 2 guy there. They seem generally quite knowledgeable but didn't have experience with Amboyna. When I told him the value of the wood he was fairly certain that they wouldn't be interested in attempting it due to the liability but maybe Dennis can stear me towards someone else.
Parker

[old3dogg]

Vac drying allows one to control the drying process better. It allows you to dry at a lower temp and gives you a better control of how fast you dry. Hot water plates under a vacuum gives you more control of how fast you evaporate water from the wood. It is a really simple process. All you have to do is find the right evaporation rate to what wood you want to dry. The only wood that I know of that wont dry from green is White Oak. White Oak must be pre-dried first. Well, 4/4 WO is pretty easy to dry in a vac kiln but anything heavier gets hard. It must be predried first.

I have never dried the wood that you are trying to dry but I am sure that there is a way.

Check out the link that Tom gave you and read more into it. Vac drying is the way to go for thick, hard to dry species.

[Chairman]

Mike:
I am sure that a vacuum kiln will do the job. The big question is of course cracks and other degradation. Also, being 8/4 stock adds to the time required. It doesn't sound like I will be doing any damage doing an initial dryout at low temps in my dehumidifier chamber. One other thing I am trying to find out more about is glycol or polymer based stabilization. As I understand these techniques if one of those is done first then I might be able to dry it much faster in higher temps without damaging the wood. Once the wood is impregnated with either of these substances, however, glues and finishes are somewhat limited. The good part is that the wood varies very little in dimension over time once either of these elements are introduced at a cellular level. So much to learn and so little time.
Parker

[old3dogg]

If done right, you will not see cracks or degrade when vacuum drying.

Sorry. But i know nothing about glycol or polymer as far as drying goes.

If done right you can dry fast at very low temps under a vacuum. How fast do you want to go?

[old3dogg]

By the way.
I checked out your site. I can see the concern in wanting not to destroy your product in the drying process!

Nice work!

[Chairman]

If I had my way I'd start up the saw and the jointer tomorrow. I know that's not realistic but it would be nice if I could find a way to get the wood dry withing three months as opposed to 2 years.

[old3dogg]

Im sure Den could find a way to dry your wood in a few weeks.

I could dry 12/4 Red Oak in 16 days. This was from 70% BMC! And this was using vac kilns from the "Fred Flintstone" days of vac drying!

Compare Amboyna to a North American hard wood for me. What  species does it compare to?

[Jason_WI]

I had to look up Amboyna to see what the heck it looked like.

http://www.gilmerwood.com/photo%20html/Amboyna_burl_photo.htm

Too busy of a grain and too $$$ for my blood.


Jason

[old3dogg]

$$$$  Thats where its at. Did you check out this guys site? Really nice looking stuff.

Seems he thinks he could make a lot more if he could find a way to dry the wood faster.

I think he can.

[serg]

Hello!
I looked yours  on your site. Beautiful and valuable work!
I can dry this tree so:
Vacuum drying technology is attractive, first and foremost because it presents a realistic opportunity to significantly decreasedrying time while preserving the quality of the wood, and often imroving it. It is known that in this regard, the capabilities of conventional drying are exhausted. More than one kind vacuum drying technology exists today. But first, a little bit about the vacuum drying process from physics' point of view.
Creating of vacuum in an environment where the drying process takes place, dramatically changes physical characteristics of heat and matter exchange processes that occur durin drying. The principal parameter that defines depth of the vacuum is the pressure in the drying environment; it is this parameter that determines the conditions and processes that occur there. The most important effect of lowering the pressure in the environment is lowering of the boiling point of water and temperature of saturated steam. The main processes that determine the kinetics of wood drying and connected with movement of moisture in liquid or steam from inside the material, and with diffusion of steam into the surrounding environment.
When part of steam/air mixture is removed and pressure is lowered, the number of molecules is decreases and their free movement increases. In a vacuum, it is significantly greater than the average microcapillary size, whose radius is less then 10-15cm. In this case, the character of molecular movement in the lumber pores changes fundamentally; effusion phenomenon occurs (Knudsen Flow). Density of the flow increases dozens of times. Additionally, with temperature of the lumber tissue being higher than boiling point with the given pressure, an excess steam pressure inside the material occurs, which significantly speeds up movement of moisture from the center to the surface of the wood. Lowering of pressure in the drying environment by 12 times speeds up the moisture movement by 4.7 times.
The above mentioned occurances during drying in a vacuum allow to achieve a certain effect when drying timber materials, compared to traditional drying. Energetic effectiveness of the process however, depends on supply of heat to the material and coducting the optimal drying mode. It is to these circumstances that we attribute creation of wide array of vacuum wood drying methods, vacuum technologies and equipment to implement them. Noteworthy is the fact that the advantages which this technology presents to the woodworking industry require complex and intricate equipment including: hermetically sealed and pressure resustant autoclave, heates which sometimes use High Frequency and Super (Ultra) High Frequency Current generators, vacuum pumps, circulation equipment, steam condensation and condensation removal systems. Practicability of using this drying system with high structural complexity is determined by a technoeconimical calculation. But simplification and lowering of equipment costs is relevant both to the producer and the consumer. For this very season we would like to call your attention to the results of an interesting development executed by the Russian company "Vacuum Plus". Developers of this kiln determined the following goals:

- Simplify constuction of the equipment and lumer drying technology.
- Achieve high quality of lumber drying.

The drying chamber consists of a cylindrical body (sizes depend on volume of the load) with an airlock. Length of the stack loaded into the chamber is 6300mm. The stack is located on a cart which is moved on guide tracks when loading and unloading the chamber. The lumber is placed on 25mm thick, 30-40mm wide with spacing, interliners calibrated according to thickness. Because of the curvilinear guides along the cart, the cross-section of the stack is not rectangular. Instead, it mimics the shape of the cylinder surface. Thus the most useful capacity possible is achieved.
Steaming, drying, heat and moisture treatment, and cooling modes are obtained emperically through the process of experimental refinement on an industrial installation. The result is a universal shedule for different breeds from initial moisture of 100% to final 5.0-6.0%, including oak of 75mm, 52mm, 32mm, walnut of 90mm thickness and others. Drying occurs on the set mode.
Developers note simplicity of maintenance of the equipment, which does not require constant presence of the operator. In the event of a power outage, the kiln automatically resumes the set operation mode when power is recoverd.
One of the advantages of this drying method, as mentioned above, is the high quality of the finished dry wood. When drying oak, moisture dispersion on the stack is 1.5%, differential for thickness of the lumber 0.5-1.0%. Drying times: hardwood leafed breeds 7-18 days, coniferous breeds 3-15 days, depending on thickness and initial moisture of 5-7%.
It seems strange at first glance to use natural circulation of the environment in the chamber, which of course lowers the intensity of the heat supply to the stack. Howeever, when treating slow-drying wood, the speed of moisture and heat exchange processes on the surface should correspond to the speed of internal moisture and heat movement. Our use of natural conductivity is one of the reasons for the high quality of drying oak and other lumber difficult in drying. The cost of this kiln is much lower than its counterparts abroad!

Additioanl dryer Information:
- Oak 60 mm thick from initial moisture of 65% dries to residual moisture of 4-5% in 18-20 days.
- Oak 60 mm thick from initial moisture of 35% dries to residual moisture of 4-5% in 10-12 days.
- Oak 25 mm thick from initial moisture of 65% dries to residual moisture of 4-5% in 9-10 days.
- Oak 25 mm thick from initial moisture of 35% dries to residual moisture of 4-5% in 7-8 days.
- Pine 55 mm thick from initial moisture of 65% dries to residual moisture of 5-6% in 8 days.
- Pine 55 mm thick from initial moisture of 35% dries to residual moisture of 5-6% in 6 days.
Our vacuum drying kiln provides 100% lumber drying of any breed (including exotic breeds) with moisture differential 0.5% for board thickness, no more than 0.9% for board length, and up to 1% for the stack.
E-mail: info@vacuums.ru

Sergey

[Chairman]

Serge:
Thanks for your response. I have no doubt that vacuum will work but I guess my question would be if you have any experience in drying this particular species? What degradation might I expect? What preparation of the wood in advance would you suggest? What would you charge? What if any warranty would you be willing to offer? Go to my website and contact me through email there and we can have a conversation. I would post my email on the forum but I don't need anymore spam.
Thanks,
Parker

[Chairman]

Mike:
To answer your question. Amboyna burl comes from the Narra tree, a very dense tropical hardwood. It is very close to Paduk, Bloodwood and Satine. I doubt it would float it's so dense. That said it also handles beautifully. I ran some through the planer at the wood dealers with standard steel blades and it cut is sweetly with no tearout.
Parker

[Den Socling]

Hi Parker,

Vacuum drying can be controlled perfectly if you can set the vapor pressure of the water in the wood and then precisely control the chamber pressure. You can make water vaporize from inside the wood. But this doesn't insure quality. A vac kiln can certainly cause cracks. You have to add humidity control for difficult to dry wood.

Our kilns can minimize humidity gradient. This keeps the outside of the wood wet while pressure gradient moves water from inside. We don't do any conditioning after drying but I have seen samples with higher MC in the shell than at the core.

You will want to be careful with DH. DH takes water from the surface like any other conventional kiln.

Figured red beech from New Zealand (a Nothofagus) was the most difficult wood that I have ever dried. A guy from Penn State was here last summer and he said that, if he were to design a difficult-to-dry wood, it would have the characteristics of red beech. I have a 'special' schedule for such wood and that is what your pieces would get. Drying time is around 18 days.

I might dry your wood but 18 days is a lot of time for our R&D kiln. I don't know if I can schedule that much.

Hey Mike,

Wait 'til you see my office. White oak paneling. Vacuum dried with no predrying. Knots and all of the pretty figure around the knots were left in.

Den

[Den Socling]

If I have the 'picture thing' straight, there should be a picture of a window in my office made with figured red beech.



And this is my office in white oak. What do you think, Mike? Is WO ugly?