Re: [ARSCLIST] Baking tapes and high frequencies

[jim@xxxxxxxxxxxxxxxxx]

> This brings up the question of whether the tape being measured for
> dimensional change was hydrolyzed and/or stretched before or after the
> recording was made.  If the damage/decay occurred after the recording,
> "baking" should return the tracks to a closer approximation of what they
> were originally.  If the tape was hydrolyzed or deformed before the
> recording was made, "baking" could alter the dimensions of the tape to a
> closer approximation of an undamaged/un-hydrolyzed state and alter tracking
> that was recorded on a deformed tape.  Makes it kind of tricky.  How do you
> accurately restore a tape to a warped or deformed set of dimensions?
>

In this particular case the baking was done after the recording. It was a tape that had an important event on it, and it was pretty hard getting it through a transport without drum sticktion that was so bad that i was concerned about stretching the tape by playing it back - and of course the playback itself was extremely unstable. Since it was a forensic matter and therefore evidence. For this reason I went to the trouble of going to several locations on the tape (which i carefully marked) and used ferrofluid and a microscope that had a stage whereby i could move the tape very carefully and make measurements. It was a pretty fancy microscope - not your "normal" scope - I had to go to a company in Rochester NY to get use of it. I did measurements before and after baking and there were changes but they were not consistent. It seemed that some areas changed differently then others, and it was not proportional. In order to do this right one would have to do an extensive analysis and see - it could have been the specific tape I used - and remember that Ferrofluid is a fluid and in fact might have put just enough moisture in that area (even though it was wiped off after use) to alter things in baking. There are too many variables as I mentioned. But as I said - in general - I did have a pretty strong feeling that in general tapes that were baked did have lower RF. BUT I dont have any statistics to back this up at all - and it could be that in certain formulations the mag particles might have been affected in a manner that would reduce their field. ON the other hand - I know that heat can in fact cause an increase in field strength and allow a transfer to other media by contact - which is the way Sony Sprinter duplicators used to work - by heating the mother that would then come into contact with blank tape and impart the field on the duplicate.

There are really so many variables here - the formulations change batch to batch and of course there were so many different formulations and product types over the years. I am afraid that the only real thing they have in common is that they were called "tape". Making generalzations is really dangerous.

I have never been a big fan of baking as I have said over the years and I have only had to use it rarely - and frequently in those cases because there were other problems - like tapes not being properly cured in the first place. I have always felt that there were other ways that just worked better and were not invasive. Baking is just one tool in the toolbox.