Sanding MDF Before Finishing

      A fine grit is best with MDF because of the material's fine, fuzzy fibers. February 27, 2015

Question (WOODWEB Member) :
Has anyone had problems sanding MDF before spraying a lacquer finish? Our finisher has had nothing but problems with getting the panels flat enough to spray. We have to sand each panel by hand with a hard block on an angle until the panel is completely flat. This is very time consuming. Does anyone have any ideas?

Forum Responses
(Architectural Woodworking Forum)
From Contributor S

Use 320 grit or so - remember itís paper not wood.

From Contributor W

Click to View Member Profile Member Photo Member Contact Info Forum Posts

Are talking raw MDF with the factory surface? That it's usually very flat.

From Contributor W:
I use two-three heavy coats of automotive primer/surfacer and then block sand with 320 before top coating.

From Contributor W

Click to View Member Profile Member Photo Member Contact Info Forum Posts

To contributor W: I see a lot of shops using that technique. It usually means a lot of material built up and then a lot of it sanded off and sucked up the dust collector. When I have people sanding and priming routed or sanded MDF, I like to have them try a very light coat of primer followed by polishing with a 280 or 320 grit, just to remove the raised fibers and slick up the surface. Then the next coat doesn't need to be so thick because the surface doesn't pop as much. I find soaking with a lot of primer to be often counterproductive.

From the original questioner:
Have you ever sanded your MDF panels through a Heesemann sander before primer?

From Contributor W

Click to View Member Profile Member Photo Member Contact Info Forum Posts

A Heesemann sander would be a great choice for sanding out sanding marks coming from the factory that produced the MDF. It might not be so great for calibrating it if that is what you need. Just remember to keep the grit pretty fine so you don't start pulling up fibers and creating a fuzzy surface that will need a lot more primer to seal. I would start with light pressure on a 220 grit silicon carbide and maybe consider a 280 grit.

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: Finishing

  • KnowledgeBase: Finishing: General Wood Finishing

    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 © 1996-2018 - 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