Re: [ARSCLIST] Info on Zonal tape required

[Scott Smith <SDSmith@xxxxxxxxxxxxxxxx>]

>From Richard:

snip:
> Another interesting note: acetate tape is theoretically subject to vinegar
> syndrome which is an autocatalytic process. The last time Jim Wheeler and
I
> had talked about it, we hadn't seen any significant quantities of VS in
> tape, while it is prevalent in film and devastating in mag film (the iron
> is a catalyst).

Richard,

I' ve pondered this a few times (especially since my nose just got a good
dose from some 1950's era 35mm fullcoat 2 days ago). As you are aware, the
base material on nearly all acetate base films is 5-6 mils thick. Also, the
coating slurry is much thicker than that used on tape (which explains why
all the old Hollywood scoring mixers loved 35 mag for it's LF capabilities).
My best guess is that the amount of both base material and oxide could
explain the prevelance of VS in mag film vs. tape. I also wonder about the
different chemical makeup of the base materials. I have seen acetate films
that have distinctly different physical characteristics. As late as the
1980's I think there were at least 4 suppliers of base material (Kodak being
one, I don't recall the others).

When we were still using millions of feet of mag stripe stock a year for
production, we saw problems with some of the base material (usually a "warp"
to the film and pack), which we traced to a change in suppliers on the part
of the manufacturer. We had the same issue will all four of our primary
suppliers, and we would regularly send back tens of thousands of feet of
film. We didn't run much Zonal then (due to the cost), but I haven't seen
the type of problems with their stock that we experienced with domestic
suppliers.

The AGFA stock we used in the 1970's was, and is, still exemplary. We have
two projects from the mid-seventies in house right now, both which have
acetate base mag film manufactured by AGFA. Not a hint of VS on any of the
reels...

snip..
>
> One theory that I have (which has yet to be confirmed) is that the typical
> cardboard box we store tape in potentially acts as an absorber of the
> excess acetic acid. We all know that old tapes seem to be stored in
> high-acid-content boxes. My question is were they made that way, or did
> they absorb acid from the tape?

We have seen quite a few reels of 16 and 35 mag come in that were stored in
cardboard boxes. Although they typically seem to suffer VS to the same
degree as films stored in cans, some reels seem to have fared better,
possibly due to the "venting" effect of the cardboard boxes. Films that have
been stored in sealed plastic bags for a long period would appear have
suffered worse, but without a long term study, it's really just a guess. I
have a roll of 17.5mm film manufactured by Kodak in 1968 that has been
stored in a vault, in a box, and has serious VS. Go figure....

--Scott D. Smith

Chicago Audio Works, Inc.

>
> Cheers,
>
> Richard
>
> Richard L. Hess                           email: richard@xxxxxxxxxxxxxxx
> Vignettes
> Media                           web:   http://www.richardhess.com/tape/
> Aurora, Ontario, Canada             (905) 713 6733     1-877-TAPE-FIX
>