DECtape madness

Jon Elson elson at
Sat Jan 13 11:04:31 CST 2018

On 01/13/2018 08:34 AM, David Bridgham via cctalk wrote:
>> So why are reels of DECtape selling for unbelievable prices on eBait? See,
>> e.g. here:
> I had those on my watch-list and just shake my head at the astonishing
> prices for the things.
> I've wondered if you might not make DECtape tape from 3/4" video tape.
> I know that DECtape has mylar on both sides but what if you somehow
> glued two strips of video tape together with the mylar backing on the
> outside.  Probably want to build a jig of some sort and I'm not sure
> what glue to use.
At Washington University, we bought 12" reels of 3/4" 
instrumentation tape and made DECtapes out of them.
The tapes were too thin, and if you left them sit too long, 
they would get print-through and start to have trouble.
As long as you used them every couple weeks, they would get 
rewound and you would not have a problem.

I don't know what you are talking about with Mylar on both 
sides. They were conventional magnetic tape, a clear mylar 
film with oxide applied to one side.  They were definitely 
made with a thicker Mylar layer than many magnetic tapes of 
the day, possibly to solve the print-through issue, but 
maybe also to prevent crimping of the tape on the pack.  I 
think the oxide formula had a more square-loop hysteresis 
curve than analog tapes, which contributed to our problem.


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