Drying Time for Black Walnut

      Dry slowly to prevent checking, and test with a moisture meter. February 26, 2005

Question
Roughly how long does it take to dry a charge of 8/4 steam treated black walnut?

Drying this material seems to be going extremely slow. In the initial stages (55%+ mc) we are only pulling about 1.5% per day from the walnut. Our schedule calls for 108 degrees and 15.5% emc (sometimes 15.0%) in the initial stages until about 50% mc or so, with about 350 fpm airflow.

I do not believe we are locking up the lumber at this schedule. Does anybody have suggestions? I would be interested to hear some of your successful steamed walnut schedules.

I am at a loss with this species. Quality-wise, the material comes out looking great, but I know it is taking entirely too much time to produce the quality.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Because of the high risk of internal checking, 8/4 walnut (steamed or unsteamed) must be dried slowly. The maximum safe rate is 3.3% MC per day, so it would be typical to average about 2% to 2.25% MC loss per day. Your temperature and air flow seem about right, so I suspect that your EMC measurement is in error slightly, which results in a slightly slower drying rate than we might expect. But, nothing wrong with being conservative with walnut...



From the original questioner:
Thanks for the info, Gene. So it is perfectly reasonable for a charge of 8/4 walnut to take 40 - 45 days?

One more question I just thought of regarding walnut. We use an 8 probe wireless moisture reading system in our kilns. It always seems like with walnut that near the end of the charge, 6 or 7 of the probes are right in our desired range. But 1 or 2 probes are usually still up in the high teens or low twenties. Everything is uniform in the kilns (air, temp, emc). What would cause this, and would you recommend dumping the kilns, or waiting over a week on 1 probe to drop for the kiln to dump (this sometimes happens on charges of cherry, as well, but less frequently)?



From Gene Wengert, forum technical advisor:
I would never use the probes to determine when to stop drying. If you ran an oven test and then compared two probes, you would find up to 10% MC difference at times. Go into the kiln and use a moisture meter with needles and test 20 pieces.

If you see wetter readings, then believe them and continue equalizing (which prevents over-drying).

For 8/4 walnut, 45 days is about the shortest you can dry from green to 7% MC. Of course, the earlier part of the schedule is the most critical.



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: Knowledge Base

  • KnowledgeBase: Primary Processing

  • KnowledgeBase: Primary Processing: Kiln Operation


    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 © 1996-2014 - 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