My understanding of Medite & Medex (exterior grade Medite) is that they are
engineered to be formaldehyde-free.  As they are both made from wood byproducts,
they will contain acids.  Secondly, I believe that they do not specify them as
being structural so they may not support weight well.

Aluminum foil or Marvelseal 360 (iron-on aluminum foil with polyethylene on one
side & nylon on the other) are both good barriers to the acids in wood.

Sue Maltby, Conservator

Quoting Ashley McGrew <[log in to unmask]>:

> Just a note here, while still superior to wood, both Medex and Medite have
> been failing oddy tests recently. Metal is still the safest bet especially in
> a closed cabinet and for particularly sensitive objects.
> 
> >>> [log in to unmask] 05/10/05 06:27AM >>>
> Joshua,
> 
> Mylar may slow down the effect of organic acids from wooden shelves but 
> it is not an effective long-term solution.Mylar is not completely 
> impermeable and it does allow a small measure of air exchange - - and 
> there are also the ends of the boards and the bottoms that will still 
> outgass.  If you had a lead or lead alloy object on those shelves they 
> could corrode very rapidly - it takes only 0.2 parts per million of 
> acetic acid to corrode lead. It would be far better to used a product 
> such as wood product such as Medite which is manufactured without the 
> organic acids that is in plywood.
> 
> Cheers!
> Dave
> 
> David Harvey
> Conservator
> Los Angeles, California
> 
> -----Original Message-----
> From: [log in to unmask] <[log in to unmask]>
> To: [log in to unmask] 
> Sent:         Tue, 10 May 2005 08:17:09 -0400
> Subject: Wooden Shelves
> 
>     From searching through prior emails, it is my understanding that a 
> sheet of mylar (or whatever it may be called today) between objects and 
> a wooden shelf is sufficient and no painting or sealing is necessary. 
>   Half of the shelves I am working with are metal, the rest are wooden, 
> probably pine, boards. 
>  
>  Thanks very much, 
>  
>  Joshua K. Blay 
>  
>  ========================================================= 
>  Important Subscriber Information: 
>  
>   The Museum-L FAQ file is located at 
> http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed 
> information about the listserv commands by sending a one line e-mail 
> message to [log in to unmask] . The body of the message 
> should read "help" (without the quotes). 
>  
>   If you decide to leave Museum-L, please send a one line e-mail message 
> to [log in to unmask] . The body of the message should read 
> "Signoff Museum-L" (without the quotes). 
> 
>     
> 
> =========================================================
> Important Subscriber Information:
> 
> The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/
> . You may obtain detailed information about the listserv commands by sending
> a one line e-mail message to [log in to unmask] . The body of the
> message should read "help" (without the quotes).
> 
> If you decide to leave Museum-L, please send a one line e-mail message to
> [log in to unmask] . The body of the message should read "Signoff
> Museum-L" (without the quotes).
> 
> =========================================================
> Important Subscriber Information:
> 
> The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/
> . You may obtain detailed information about the listserv commands by sending
> a one line e-mail message to [log in to unmask] . The body of the
> message should read "help" (without the quotes).
> 
> If you decide to leave Museum-L, please send a one line e-mail message to
> [log in to unmask] . The body of the message should read "Signoff
> Museum-L" (without the quotes).
> 

=========================================================
Important Subscriber Information:

The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).

If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).