Hi Jonathan,

I can only say that I have experienced the same phenomenon and with red
lacquer as well as black. The red lacquer discs have had areas (or large
spots) that are more translucent yellow. The black lacquer discs that I
have seen this on are as you describe. Until your post, ("some discs
have it and some don't from the same collection that has been stored in
the same place for 65 years") I had assumed that it is storage related
since I receive discs for transfer from all over the world. I don't have
any current examples since the original analog carrier gets returned to
the customer.

Regards,

Corey
Corey Bailey Audio Engineering
www.baileyzone.net








On 6/24/2016 12:04 PM, Richardson, Jonathan Carrithers wrote:
> Hello everyone,
>
> To those who have worked with lacquer discs I have a question. Have you ever encountered a disc that has turned yellow or brassy copper? I have run across a multiple discs with this strange coloring. The only thing I can guess it might be is some kind or reaction the lacquer has with the air but I am wondering why some discs have it and some don't from the same collection that has been stored in the same place for 65 years. It can't be oxidation and it mainly occurs where the hole in the sleeve was, sometimes on the edge of the disc. When looked at under a microscope it almost seems translucent. Any information will help.
>
>
> here is a picture
>
>
> https://drive.google.com/file/d/0B4OPruHNUu42TVpUcHl0X2FJZmM/view?usp=sharing?
>
>
> Jonathan
>
>
> Jonathan Richardson
> Audio Visual Specialist
> Media Digitization and Preservation Initiative
> Indiana University
> 812-320-8485
> [log in to unmask]
> https://mdpi.iu.edu/???
>
>
>
>
> ?
>
>