Of Stripes and Recording ...

[Lee McCaffrey]

All magnetic tape (be it for audio, video or data storage) is made the same way, a slurry is deposited onto a substrate in a thin layer, this slurry then solvent welds to the the substrate so the resultant stripe becomes physically fused with the substrate. After the paste is applied the substrate is passed over a strong magnet which aligns all the magnetic particles in the paste to the correct orientation (so it can be recorded upon), it then dries and cures while being passed through chrome rollers which flatten and smooth the surface to the correct surface finish.
So whether an 8mm film has the stripe directly applied via paste or laminated with a thin strip of tape, that tape was too made with a magnetic paste (so to speak). There's just an extra step or two along the way. When people refer to 'bad' paste they mean Derann's grey paste stripe, but the earlier brown stripe also had it's fair share of problems.
Reading the old literature it looks like the grey paste was some sort of 2-part resin which gave the level of adhesion required, but also ended up being thicker than previous mixes. It would also 'go off' (ie get thicker, start to harden) during striping, limiting the amount of film that could be striped at a time to a few thousand feet before the machine had to be cleaned and stripped. I would imagine the actual stripe material itself is no more abrasive than other magnetic stripes, but its uneven rougher surface will accelerate wear. Think of lower grit sandpaper vs high grit.

[Osi Osgood]

So, in theory, the stripe that starts as a "paste", that is applied to the film surface, would technically have potentially a better sound quality than stripe that is already manufactured, and then "glued" to the film surface? Another question, in paste laminate, the glue is already in the "🧲" paste itself? Where, in the already manufactured stripe, there is no glue in the production of the stripe? In that case, it would seem, in my opinion, that the magnetic stripe that has no glue in the "mix", would deliver a higher quality of sound reproduction? ( Bear in mind, my opinion is an uneducated opinion).

[Brian Fretwell]

I believe Ged wrote that the first attempt to stripe at Derann didn't have the resin in the mix and it proptly dropped off the film during later processing!

[Lee McCaffrey]

Osi it is not a 'glue' to speak of. The magnetic slurry is essentially the same material as the film base (so either celluloid acetate or polyester) dissolved in a suitable solvent with the magnetic particles suspended within it. If you were to paint it onto an inert surface it would dry quickly and form a thin plastic film. When applied to the film base however the solvent dissolves the surface of the base, as the solvent evaporates (it is very volatile) the resulting film layer is effectively welded to the base. Remember this is the same process for mass-produced audio tape for cassettes/reel to reel as it is for striped film stock.
When Kodak updated their LPP they added a lubricant layer, this was most likely the reason the paste stripe failed to take to the surface. I'm guessing the added resin was aggressive enough to cut through this lubricant, perhaps stripping this lube beforehand would have allowed using the classic brown stripe (which Alberto uses).

[Osi Osgood]

That is fascinating! At least for me, this has been one of the educational series of posts!

[Brian Fretwell]

Osi it is not a 'glue' to speak of. The magnetic slurry is essentially the same material as the film base (so either celluloid acetate or polyester) dissolved in a suitable solvent with the magnetic particles suspended within it. If you were to paint it onto an inert surface it would dry quickly and form a thin plastic film. When applied to the film base however the solvent dissolves the surface of the base, as the solvent evaporates (it is very volatile) the resulting film layer is effectively welded to the base. Remember this is the same process for mass-produced audio tape for cassettes/reel to reel as it is for striped film stock.
When Kodak updated their LPP they added a lubricant layer, this was most likely the reason the paste stripe failed to take to the surface. I'm guessing the added resin was aggressive enough to cut through this lubricant, perhaps stripping this lube beforehand would have allowed using the classic brown stripe (which Alberto uses).

I believe Derann only striped Agfa stock, which they used when Kodak pre-striped stock was withdrawn.

[Lee McCaffrey]

Ah yes, I had forgotten Kodak stopped producing double-rank 16mm stock. So there must have been something different about the Agfa stock that caused the stripe to peel off.

[Osi Osgood]

Slightly off topic, when was Kodak pre stripe film stock discontinued?

[Philip Hamilton]

This is a fascinating thread with lots of information for those who want a deep dive on this subject like me. LOL. So Alberto in Italy uses the paste but somehow has no problem that I am aware of regarding adhesion to LPP. I have some of his striped film and all seems well.

Andec in Germany I *think* uses Alberto for striping and recording features. But for digest or shorter reels uses another German company that lays on a laminate stripe - single track - as I understand. I also have a few reels with the process and no problem at with adhesion to the LPP - at least as of this writing.

What I find really strange is that it appears only in Germany and Italy that striping is being done as a service and that NOWHERE in the USA this is available.

Makes getting new releases on Super 8mm more costly for sure.

Fascinating thread … and fingers crossed that the striping on my new Super 8mm releases outlives me.

[Osi Osgood]

It wouldn't seem to be that much of an issue to have striping firm in the U.S. splitting existing magnetic tape shouldn't be an issue. Having just the right formula for the glue might be another issue. Was the glue used a copyrighted formula, or is it something that can be easily manufactured? Good to see ya, Phillip!

[Steve Lee]

Hi Osi.
I do remember reading years ago that when Kodak produced it's pre striped stock that this was acitate based stock, the adesive used to bond the mag stripe wasn't actually adhesive more like a acetone formula.
This slightly melted the film base and welded the mag stripe to it. This is why it is indestructible, there is no way this is coming off.
Also by melting the edges of the stock, this reduces the thickness on the area where the mag stipe is to be placed by a micron or two, so when the stripe was attached it didn't stand so proud above the stock.

The same can't be said for polyester base stock. There are so few substances which will adhere to polyester, it just repels them. The oxide/paste/liquid stripes that are driped onto the polyester base stock are always going to sit proud of the film stock, almost like railroad tracks.
Due to the problems that can arise from performing this act, anything slight deviation such as the speed of the film passing and the flow rate of the paste, such as blockages are going to affect the final results. It's like trying to line pipe icing onto a cake.

My biggest concern is with the flexibility of the film as it passes through a projector mechanism, as it needs to flex in both directions to do so. Will this eventually break the bond between the paste and the film base?. I guess we will only find out with time.

[Osi Osgood]

Is there any chance of paste magnetic flaking off of the film? If not presently, is it only a matter of time? In that case, optical sound super 8 reigns supreme, as it's printed directly on the stock. ( Snicker ).

[Paul Adsett]

Can I ask a dumb question? Are reel-to-reel tape recorders still being manufactured/in use?

[Lee McCaffrey]

I think it's fair to say that if the stripe hasn't come off after 30 odd years it's probably not going to. If modern prints are done the tried-and-tested way they should be fine also, to say otherwise is simply fear-mongering.

Reading FFTC 17 (dated Nov. 1990) it seems Derek got the news about Kodak discontinuing pre-stripe early 1990, which was when the task of acquiring/setting up the striping machine began. In the article it mentions how the supply of pre-stripe was dwindling during the setup process, I can only assume Derek had the labs buy in as much of the remaining pre-stripe as possible before it was gone forever. So the transition period was most likely 1991

Paul as far as I know people are still operating/maintaining reel-to-reels. I think new heads are available from Photovox but I don't know for how much. Obviously recording studios are still using analogue tape so there will always be some kind of market for it. It's worth remembering that even tough most consumer media now is digital there is still magnetic media in the form of bank cards, HDDs with platters, even data storage like LTO tapes. These all require some form of magnetic head for reading/writing. So the technology to make heads exists still, it's just migrated to other areas.

[Steve Lee]

Hi Paul, no there isn't any companies that produce new reel to reel machines today. There is a company in the U.S that take old Tascam machines and totally refurbishes and rebuild them. They replace basically everything from new preamps new servo motors you name it, but this dosn't come cheep. I think they start around $20,000 for the basic model.