Hi, Andreas,
I have written about 3M 175 in several articles. In chronological order:
https://richardhess.com/notes/2006/07/12/the-beginning-of-3m-175-squeal/
Mentioned tangentially and another approach:
https://richardhess.com/notes/2007/11/08/success-with-squealing-shamrock-031-tape/
A further bit of analysis and comparison:
https://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/
(search for "175" (without the quotes) and it's the second hit from the top.
Discussion of 176 follows immediately after.
Cold playback has proven to be helpful, and that generally indicates
that there has been binder degradation in the sense that the binder has
become more rubber-like than glass-like due to the glass transition
temperature being lowered as the tape degrades. Cold playback just
lowers the playback temperature below the current glass transition
temperature (Tg) of the tape. Ric Bradshaw tested some 3M 175 for
me--and here the Tg had dropped to about 8 °C. 4 °C is a common
cold-playback temperature.
A fairly lengthy discussion of this appears starting a little more than
half way down on p. 250 of my 2008 ARSC Journal article, found here:
https://www.richardhess.com/tape/history/HESS_Tape_Degradation_ARSC_Journal_39-2.pdf
The bottom of page 252 is Bradshaw's comment on the 175 sample he tested
for me. There are many interesting points raised in this quote. I think
that Bradshaw's "greasy" and your "oily" might be both describing a
similar byproduct.
> My experience with gamma iron oxide filled, BF Goodrich Estane
> polyester-polyurethane
> based formulations from the late 60’s and 70’s is that they ALL had
> Tg’s at time zero of
> barely 26–30°C, and as they aged and hydrolyzed it dropped to less
> than 12-15°C. I really
> believe this is why [cold playback of] many of these tapes improves
> their runability. For
> hydrolyzed tapes, an increasing amount of the binder is cleaved and
> produces greasy, low
> melting degradation fragments which prefer to migrate to the surface
> and for back coated
> media move into the backcoat causing it to be “sticky” at room
> temperature. Baking tapes
> with this kind of degradation can force even more migration and
> ultimately “glue” the
> two coatings together unless the bake is done with very low wrap
> tension (interlayer pressure).
> I think that wiping with a Q-tip or any wipe for that matter is
> removing some of
> the degradation fragments (I imagine the wipes get very brown from
> coating removal as
> well) and thus improving the unwind and play. The problem with doing
> this for the
> length of a tape is that you are also removing what is left of the
> lubricants and the
> degraded coatings have lost much of their rubbery (resilient)
> toughness. It would be better
> to do a two part wipe, using a damp isopropyl alcohol wipe followed by
> a butyl stearate
> (lubricant) (about 5% by volume in hexane) wipe to not delube the
> magcoat. You have to
> build a rewind station with two wipe heads in series to do this
> satisfactorily. We used to
> have one to handle 3420 reel to reel digital tapes.
So, there is a bunch of information here, but I do not think we have a
definitive procedure for all 3M175, since different reels appear to
behave differently. This seems to be a problem with many
manufacturers...not to mention the often-found problem of Tape Type ABC
in Tape Box XYZ.
Cheers,
Richard
On 2022-10-27 4:23 p.m., Andreas Meyer wrote:
> Thank you Dennis,
>
> I always welcome your experience and expertise. Curious we had no problems
> so far with the 176 stock (again same full track mono at 7.5ips). I
> decided to try a *light* baking of the 175 stock, but this did not reduce
> the oily deposit on the head for playback. I would like to get these under
> a scope as this is not back coating causing the typical sticky shed
> syndrome. There is no backing on the 175 stock. But I do want to see if
> the oil leaving the tape is causing damage before I go further. I will read
> up on the AES paper that was linked earlier in the thread and see if this
> can shed some light on the situation (pun intended).
> Thank you all,
> Andreas
>
> On Thu, Oct 27, 2022 at 1:30 PM Dennis Rooney<[log in to unmask]>
> wrote:
>
>> My experience with 176 and 177, from their introduction in the seventies,
>> is that both shed quite a bit after fewer than one or two years, but I
>> never encountered any oily deposits. As a utility formulation, they worked
>> well in our newsroom operations, and were occasionally used for field
>> recordings of concerts, although they were never a first choice for that
>> purpose.
>>
>> DDR
>>
>> On Thu, Oct 27, 2022 at 11:26 AM Andreas Meyer<[log in to unmask]>
>> wrote:
>>
>>> Hello Tim,
>>>
>>> No, nothing was applied to these reels, they are coming from a library
>> that
>>> I trust. The format is full track mono and it ran at 7.5ips. The
>>> interesting thing is my initial test didn't show any shedding, no
>> deposits
>>> and then played fine for half the program. I could hear edits between
>> two
>>> machines as they overlapped for live concert - and the machines had
>>> different azimuth settings (I had to adjust every time they switched
>>> machine source). But about an hour into the program, I realized there was
>>> more going on than just an azimuth adjustment. Sure enough, there was an
>>> oil residue on the heads. The stock from both machines looks the same,
>> and
>>> the boxes are the original Scotch 175 boxes, so I have no reason to
>> believe
>>> they were running different stock. I am treating the tape now so I will
>>> update with my progress.
>>> Best,
>>> Andreas
>>>
>>> On Thu, Oct 27, 2022 at 7:07 AM Tim Gillett <[log in to unmask]
>>>
>>> wrote:
>>>
>>>> Hello Andreas,
>>>>
>>>> Not open reel but this week I had in a cassette (Ampex Plus Two). It
>>>> was sticking or slowing for the owner. The owner's other
>>>> cassettes had transferred perfectly for him. I seem to recall this
>>>> Ampex type has squealed or stuck for me in the past.
>>>>
>>>> The owner applied a lot of spray silicon lubricant to the entire tape
>>>> inside the cassette. It didnt solve the problem and probably made it
>>>> worse by making the tape too slippery for the capstan and pinch roller
>>>> to grip it. Using Isopropanol as a solvent I thoroughly cleaned
>>>> the oil from the tape, both sides. The tape then played all the way
>>>> through without a problem.
>>>>
>>>> Is it possible some sort of oil had similarly been applied by someone
>>>> to the 3M 175 in an attempt to stop it squealing?
>>>>
>>>> Cheers
>>>>
>>>> Tim Gillett
>>>>
>>>> ----- Original Message -----
>>>> From: "Association for Recorded Sound Discussion List"
>>>> <[log in to unmask]>
>>>> To:<[log in to unmask]>
>>>> Cc:
>>>> Sent:Wed, 26 Oct 2022 19:38:04 -0400
>>>> Subject:Re: [ARSCLIST] [EXTERNAL] [ARSCLIST] Scotch 175 verses 176
>>>>
>>>> Hello.
>>>> Well i don't have squeal with the 175, but i have oil deposit. Enough
>>>> to
>>>> give me a high
>>>> Frequency reduction. The 176 is playing off fine.
>>>> Thanks.
>>>> Andreas
>>>>
>>>> On Wed, Oct 26, 2022, 17:58 Shai Drori<[log in to unmask]> wrote:
>>>>
>>>> > The 175 and 176 are totally different tapes. The 176 was a general
>>>> purpose
>>>> > tapes used extensively in radio ( and in Israel also for some music
>>>> > production). It is extremely reliable and stable, and still
>>>> performs well.
>>>> > The 175 is showing signs of loss of lubrication. Richard Hess’s
>>>> paper is
>>>> > right on the mark. In my experience the 175!is usually a major
>>>> squealer,
>>>> > like the PR150.
>>>> >
>>>> > On Wed, 26 Oct 2022 at 19:15 Gary A. Galo <
>>>> >[log in to unmask]> wrote:
>>>> >
>>>> > > Hi Andreas,
>>>> > >
>>>> > > Are you saying that the 175 you have has back-coating? 176 and
>>>> its 1 mil
>>>> > > counterpart, 177, were not back coated, and I didn’t think 175
>>>> was
>>>> > either.
>>>> > > Richard Hess has a post on loss of lubrication in 175:
>>>> > >
>>>> > >
>>>>
>> https://richardhess.com/notes/2006/07/12/the-beginning-of-3m-175-squeal/
>>>> > >
>>>> > > Best,
>>>> > > Gary
>>>> > >
>>>> > > -----Original Message-----
>>>> > > From: Association for Recorded Sound Discussion List <
>>>> > >[log in to unmask]> On Behalf Of Andreas Meyer
>>>> > > Sent: Wednesday, October 26, 2022 12:05 PM
>>>> > > To:[log in to unmask]
>>>> > > Subject: [EXTERNAL] [ARSCLIST] Scotch 175 verses 176
>>>> > >
>>>> > > This message did not originate from SUNY Potsdam or one of its
>>>> trusted
>>>> > > senders. Do not open attachments, click on links, or provide your
>>>> > > credentials if the source is suspicious.
>>>> > >
>>>> > >
>>>> > > Greetings,
>>>> > >
>>>> > > Curious if someone has details on the difference of Scotch 175
>>>> stock
>>>> > > versus 176. I am noticing slight shedding on the 175 whereas the
>>>> 176
>>>> > seems
>>>> > > stable (vintage 1973). The shedding is more oily rather than
>>>> actual back
>>>> > > coating.
>>>> > >
>>>> > > Thanks in advance.
>>>> > >
>>>> > > Andreas
>>>> > >
>>>> > > --
>>>> > > *Meyer Media LLC / Swan Studios NYC
>>>> <https://meyer-media.com/index.html > >*
>>>> > > 77 East 110 Street
>>>> > > New York City, NY 10029
>>>> > > 917-639-3312
>>>> > >
>>>> > --
>>>> >
>>>> > Cheers
>>>> > Shai Drori
>>>> > Expert digitization services for Audio Video
>>>> > 3K scanning for film 8mm-35mm
>>>> > Timeless Recordings Music Label
>>>> >www.audiovideofilm.com
>>>> >[log in to unmask]
>>>> >
>>>>
>>>> -------------------------
>>>> Email sent using Optus Webmail
>>>>
>>
>> --
>> 1006 Langer Way
>> Delray Beach, FL 33483
>> 561.265.2976
>>
--
Richard L. Hess email:[log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm
Track Format - Speed - Equalization - Azimuth - Noise Reduction
Quality tape transfers -- even from hard-to-play tapes.
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