Vacuum Metal Deposition

[mpvisc00]

I am hoping someone out there who has access to a Vaccum Metal Deposition chamber can help me with some technical difficulties. We are doing a validation study on our VMD unit, and have run into an issue with plastic sandwich bags and ziploc bags. We've been unable to get these two types of plastic to develop.
The first time I processed the items, the windows of our chamber covered over with zinc prior to any development. On subsequent runs, the same thing happens. Finally, I varied the amount of gold hoping that it would build enough of a coat for the zinc to deposit, to no avail. There was very minimal development around any ridge detail, and only sporadic hints of zinc deposition elsewhere on the plastic.
Has anyone had these issues with VMD? or have any solutions? Other types of plastic have worked wonderfully, such as plastic grocery bags, acetate lift-backs, etc.

Thanks in advance.

[Ernie Hamm]

Not sure this will address your concerns as I no longer have this issue (My JFI collection has been donated) and this comes from my reference index entry, but you may find information at the following: “Alternative Metal Processes for Vacuum Metal Deposition Alternative Metal Processes for Vacuum Metal Deposition”, David Phippson and Stephen Bleay, JFI, 57:2 (2007) Comment: Tests using silver in place, or in addition to, zinc or gold techniques in VMD procedure. A correction of an illustration in the article is in JFI, 57:3 (2007).