Re: [ARSCLIST] Oxide flaking off tape from the 1950's

["Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>]

Quoting Mike Csontos Mwcpc6@xxxxxxx:


> I have found reels of the cheap green boxed "Shamrock" brown oxide mylar
> tape
> that shed oxide in sheets leaving clear base.  That is probably why it ended
> up in those boxes.
>
> The oxide sheets just fell off as the tape was unwound; no bond to the base
> at all.  It would be very hard to salvage.
>
Mike,

That is indeed interesting. I've seen clear "leader" where the oxide has come
off where the tape was threaded and handled, but we've traced that to high
humidity and the tapes have begun healing themselves when the humidity has
dropped. In this archive, we saw daily variations between 50 to as high as 75%
RH as the "Economizer" all-outside-air cycle was activated over night.

In my home studio, where the RH is 30-40%, the tape actually became less
fragile over four or five months.

I wonder how the Shamrock was stored.

Thanks,

Richard