At DAK we got our binder and dry oxide from MagNox, these were mixed in a drum mixer along with MEK as a thinning agent that also improved adhesion to the base polyester (aka dupont mylar) film.
Mag tape coating is similar to the first step in Offset printing. The oxide (ink) is supplied to a roller and passes through a metering blade that leaves a smooth thin layer of oxide on the roller that rotates against the film base and transfers the oxide coating.
Traveling through an oven evaporates the solvent and begins to harden the coating, which next passes through calendar rollers which smooths and compresses the oxide coating under pressure and heat to finish hardening the coating.
Two types of calendar rollers were used with different tape surface textures. A Nylon roller would leave a soft matte finish while a hard chrome roller would give the oxide a highly polished sheen which looked nice but would cause increased odixe to tape head adhesion because of the lack of microscopic air pockets in the oxide..... often to the point of squealing noise.
The highly polished hard chrome surface was mostly used for video and high speed instrumentation tape.
At DAK we coated on 6-8-12" web widths. Rotary slitters converted the webs to 1/8" cassette and 1/4" reel stock into master pancakes.
One step that could contribute to oxide flaking is the calendaring processing where pressure and heat are critical to long term adhesion.
The hard chrome finished surface of the oxide can contribute to head/tape squeal due to surface adhesion. The hard chrome finish at one time was promoted as providing few drop outs and more uniform output in Master tape products when used at higher tape speeds.... where did the seconds end up ? you guessed in the bargain boxed 3M and Ampex, which accounts for the inconsistency of the bargain box stock.
Also the Melody brand used reslit 1/2" computer stock that was returned to the mfgr for credit toward new stock... it was part of a gov buy back program... again nothing goes to waste, find a way to reuse it.
Even DAK secured 1000's of reels of computer and instrumentation tape to be reslit.
d nelson ward
Beautiful Music you will never forget, at; http://www.americanbeautiful.podbean.com/
--- On Fri, 4/5/13, Richard L. Hess <[log in to unmask]> wrote:
> From: Richard L. Hess <[log in to unmask]>
> Subject: Re: [ARSCLIST] Sticky SHRED/tape chemistry
> To: [log in to unmask]
> Date: Friday, April 5, 2013, 4:44 PM
> My understanding was that BF Goodrich
> Estane was used widely as the binder.
> Dr. Bob Perry would not share any Ampex secrets with me and
> said at the
> time they were still secrets in his mind.
> PDF page 6 of my paper discusses this a bit more formally
> than my
> previous post.
> This would be useful information...
> Let's all rattle whatever cages we can.
> On 2013-04-05 6:56 PM, Dan Nelson wrote:
> > Back in the 80s i was working for DAK industries and we
> were coating our own webs and slitting 1/8" and 1/4" stock.
> Before that i was familiar with Northridge magnetics
> who was making mastering quality 1/2" tape.
> > In fact i set DAK up to buy the Northridge facility.
> > MagNox was a prime supplier of odixe and coating
> chemistry to the industry as a whole.
> > IM looking for my folder of spec sheets which i thought
> i may have kept when the Air Quality Inspections in LA
> made it impossible to use the quantity solvents needed
> and DAK shut down the coating plant.
> > Our next step was buying raw stock from Ampex here on
> the West coast.
> > So any problems Ampex had in the 80s was passed onto
> DAK labeled products.
> > d nelson ward
> > Beautiful Music you will never forget, at; http://www.americanbeautiful.podbean.com/
> > --- On Fri, 4/5/13, Tom Fine <[log in to unmask]>
> >> From: Tom Fine <[log in to unmask]>
> >> Subject: Re: [ARSCLIST] Sticky SHRED
> >> To: [log in to unmask]
> >> Date: Friday, April 5, 2013, 3:23 PM
> >> Richard, do any of these researchers
> >> know the actual "recipes" for the tapes they are
> >> If not, is it possible to get that knowledge? Has
> >> interviewed in detail the tape manufacturers'
> chemists? It
> >> sounds to me like we have a bunch of stabs in the
> dark and
> >> theories. Are first-person details of actual
> recipes already
> >> non-attainable?
> >> Also, I would think a modern manufacturer like Mike
> Spitz or
> >> Zonal could shed some light, perhaps talking about
> >> companies recipes rather than their own?
> >> I really think it's time to get down in the weeds
> with the
> >> chemistry, I can't see why the whole process of
> >> is not understandable, quantifiable and
> >> -- Tom Fine
> >> ----- Original Message ----- From: "Richard L.
> Hess" <[log in to unmask]>
> >> To: <[log in to unmask]>
> >> Sent: Friday, April 05, 2013 6:02 PM
> >> Subject: Re: [ARSCLIST] Sticky SHRED
> >>> Hi, Nigel,
> >>> Thank you for this very useful insight! This
> has been
> >> part of the mantra for a long time, but it is
> wonderful to
> >> receive further confirmation.
> >>> We cannot forget the "running changes" that
> >> Thiebaut discovered specifically in U-Matic tapes,
> but I
> >> suspect that process "improvements" were common as
> >> were running and if this 60-70 % factor is involved
> >> doesn't even have to be a process improvement.
> >>> Cheers,
> >>> Richard
> >>> On 2013-04-05 4:53 PM, Nigel Champion wrote:
> >>>> At last year's IASA conference in New
> >> Dietrich Schueller presented information gleaned
> >> discussions with retired employees of the major
> German tape
> >> manufacturers, BASF & AGFA. Some expressed the
> >> that subtleties in the manufacturing procedures had
> >> influence on the finished quality of magnetic tape
> than the
> >> actual chemical mix by a factor of 60% or 70%.
> >>>> I infer from this that, even if one tape
> >> exactly the same chemical constituents as another,
> a small
> >> variation in one step of the manufacturing
> processes can
> >> result in pronounced differences in measures of
> quality such
> >> as performance, stability and/or longevity.
> Such a
> >> situation makes comparisons very difficult at this
> >> stage for those considering chemical analysis of
> >> constituents or assessing differing degradation
> >> controlled climatic conditions as suggested
> recently on this
> >> list for sticky-shed. It would also explain
> >> differing experiences of many on this list with the
> >> tape.
> >>>> Nigel
> >>>> ________________________________________
> >>>> From: Association for Recorded Sound
> >> List [[log in to unmask]]
> >> on behalf of Tom Fine [[log in to unmask]]
> >>>> Sent: 06 April 2013 07:23
> >>>> To: [log in to unmask]
> >>>> Subject: Re: [ARSCLIST] Sticky SHRED
> >>>> I think Dennis is bringing up a really
> >> point. Sarah and Richard, do you have any contacts
> >>>> with original tape manufacturer chemists,
> >> who were familiar with the "brew" of the tapes?
> >>>> Before these people die, it's important to
> >> information from them about what chemicals were
> >>>> in the binders. There's no "state secret"
> >> -- all of those tape manufacturers are out of
> >>>> business now (and I'm afraid, given how
> >> work, that corporate records detailing the "brew"
> >>>> probably lost to time).
> >>>> <SNIP>
> >>>> -- Tom Fine
> >>> -- Richard L. Hess
> >> email:
> [log in to unmask]
> >>> Aurora, Ontario, Canada
> >> 647 479 2800
> >>> http://www.richardhess.com/tape/contact.htm
> >>> Quality tape transfers -- even from
> >> tapes.
> Richard L. Hess
> email: [log in to unmask]
> Aurora, Ontario, Canada
> 647 479 2800
> Quality tape transfers -- even from hard-to-play tapes.