Vacuum Dried Red Oak

      Achieving quality and color. May 19, 2004

How many of you have used red oak lumber that was dried in a vacuum kiln? How much stress do you run into? Nothing to worry about? Enough to be a problem? Is there anything you like or dislike about lumber dried in a vac kiln?

Forum Responses
From contributor D:
Not all vacuum kilns are created equally.

Besides better color, I often hear that it's more machinable.

From the original questioner:
I don't feel that our vac kilns cause a great amount of stress. All I am trying to do is prove it. Years ago, when they dried 200,000 BFT of lumber through our vac kilns, the greatest complaint was stress. That was then. This is now. Some things have changed.

I should also add that color isn't a problem with maple, but it is with the sapwood in oak and cherry. It works well to steam the cherry. Steaming red oak for color change is a pipe dream.

From Gene Wengert, forum technical advisor:
The picture below shows two pieces of red oak lumber that were cut in half. The left half was steamed (Elder Steaming Process) while the right ends were not processed (N.P.). After steaming, the lumber was dried identically and then planed. The lack of gray stain and the brightness of the sapwood can easily be seen.

From the original questioner:
How was the oak dried? When I tried steaming red oak and then drying in a vac kiln, all I got was a lot of bow and honeycomb.

P.S. I started my kiln charge of 4/4 RO at 100/98.

From Gene Wengert, forum technical advisor:
The oak was air dried and then kiln dried.

From contributor D:
Have you ever thought about steaming inside a vac kiln?

From the original questioner:
How the heck would you get steam to the center of the load?

From contributor K:
The only experience I have had with a vac kiln was with a company who wanted to sell us a RF vac kiln. They told us they could dry 8/4 red oak in a couple days with no degrade. They even went so far as to dry some 8/4 for us for free. After drying there was degrade due to checking, along with a variance in MC among the boards, and stress in the lumber. Needless to say, we were not impressed and did not purchase one of their kilns, nor do we plan to.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor H:
We have dried 35 mm French oak in our WDE/Maspell vacuum kiln in five days without defects. We usually do 4/4 or 2/4 for parquet boards and when properly stacked and air dried, we have no stress, no cupping, excellent and fast drying capabilities. It's using superheated steam as a heating medium at 150 mbar.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Lumber and Plywood

  • KnowledgeBase: Primary Processing

  • KnowledgeBase: Primary Processing: Air Drying Lumber

  • KnowledgeBase: Primary Processing: General

  • KnowledgeBase: Primary Processing: Kiln Operation

  • KnowledgeBase: Wood Engineering: Wood Properties

  • KnowledgeBase: Woodworking Miscellaneous

  • KnowledgeBase: Woodworking Miscellaneous: Woodworking

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2021 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article