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Tape Degradation Factors and Predicting Tape Life

Learn about the degradation factors affecting analog recording tapes, preservation challenges, base film types, binder failures, and solutions. Understand the risks associated with different base film materials and degradation modes.

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Tape Degradation Factors and Predicting Tape Life

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  1. Tape Degradation Factors and Predicting Tape Life Richard L. HessAurora, Ontario, Canada

  2. Dietrich Schuller says: “The world's stock of audio recordings is estimated to be more than 50 Mh (million hours) of materials.… “None of these recordings are on permanent carriers…” Richard L. Hess ARSC Milwaukee 2007-05-04

  3. King’s College London says: “Seventy percent of all audiovisual material is under immediate threat of deterioration, damage or obsolescence — and seventy percent of collection managers don't know it. Richard L. Hess ARSC Milwaukee 2007-05-04

  4. The Challenge • Archives hold tapes from the 1940s on • The tapes are degrading • Few new playback machines are made • Multiple factors involved in the degradation • Only limited research has been done • Recommendations for tape differ from film • Some tapes may degrade before it’s their turn to be copied Richard L. Hess ARSC Milwaukee 2007-05-04

  5. Conceptual Timeline Richard L. Hess ARSC Milwaukee 2007-05-04

  6. Components • Base film • Binder/oxide • Lubricant • Back coating (later tapes) • All contribute in varying degrees to tape degradation Richard L. Hess ARSC Milwaukee 2007-05-04

  7. Base film degradation modes • Acetate • Vinegar Syndrome • Brittleness/Drying out, Shrinkage • Polyester (PET) • Warping, especially with tensilized PET • PVC and Paper • Slow weakening due to aging Richard L. Hess ARSC Milwaukee 2007-05-04

  8. General degradation modes • Tape pack defects • Spoking • Folded wraps • Popped strands • Reel defects • Weak hubs • Warped flanges Richard L. Hess ARSC Milwaukee 2007-05-04

  9. Acetate base film • 1935–1972 • Vinegar syndrome slowed by freezing • Freezing is considered bad for tape • Vinegar syndrome is left to advance, but it is doing so slower than film • Will it plateau or continue? • Canadian Conservation Institute has plans to research freezing tape Richard L. Hess ARSC Milwaukee 2007-05-04

  10. Acetate degradation 1943 German Acetate tape showing cracking and corrosion caused by the acetic acid of “vinegar syndrome” and related shrinkage Corrosion Reel window imprint From the Ampex Museum collection at Stanford, photo by author Richard L. Hess ARSC Milwaukee 2007-05-04

  11. PVC & Paper base film • Degradation is not as fast as acetate • Paper in general is known to respond well to freezing • So far, PVC tape has been stable • There is worry about the plasticizers in PVC tape • PVC was made 1943–1972 • Paper was made 1940s–1950s Richard L. Hess ARSC Milwaukee 2007-05-04

  12. PET: Polyethylene terephthalate • Also known as Mylar (DuPont TM) • Generically called a Polyester • PET is probably the most stable and least problematic of historic base films • Tensilized PET is potentially more problematic (aka Tenzar, 3M TM) • It is hygroscopic and can move water to the back of the coatings Richard L. Hess ARSC Milwaukee 2007-05-04

  13. Binder failures • Soft Binder Syndrome (SBS) • Sticky Shed Syndrome (SSS) • Pinning / Blocking • Binder-base adhesion failure Richard L. Hess ARSC Milwaukee 2007-05-04

  14. Soft Binder Syndrome (SBS)  • Tape squeals, may leave some debris • Baking may or may not solve problem • If baking works, then it is Sticky Shed Syndrome • Sticky Shed is a subset of SBS Richard L. Hess ARSC Milwaukee 2007-05-04

  15. Soft Binder Syndrome Causes • All SBS seems to be caused by binder hydrolytic breakdown • Polyester-Polyurethane binders suffer most • Glass transition temperature Tg is lowered • Tg is the temperature above which the substance becomes rubbery • It can be below room temperature Richard L. Hess ARSC Milwaukee 2007-05-04

  16. Soft Binder Syndrome Tg • 3M 175 – Currently Tg ≈ +8°C (46°F) • One reel of 175 did not immediately respond at about 38°F (3°F), but did after two days of cold soak • Removing moisture may raise the Tg somewhat • The reactions are not truly reversible in a filled matrix Richard L. Hess ARSC Milwaukee 2007-05-04

  17. Soft Binder Syndrome Solution • Since the Tg has become lower • It’s difficult to raise the Tg • We wish to play the tapes • What can we do? • One solution suggests itself… Richard L. Hess ARSC Milwaukee 2007-05-04

  18. Soft Binder Syndrome Solution Richard L. Hess ARSC Milwaukee 2007-05-04

  19. Soft Binder Syndrome Solution • This worked with 3M/Scotch 175 • This worked with Sony PR-150 • Both of the above tapes were • Previously unplayable • Did not respond to baking • Partially responsive to relubrication Richard L. Hess ARSC Milwaukee 2007-05-04

  20. Soft Binder Syndrome Solution • ALL heads and guides were in place for this test • We used the high tension (large reel) setting to make this a tougher test • Environment approx +4 °C; 25% RH • This has worked in other tests as well Richard L. Hess ARSC Milwaukee 2007-05-04

  21. Soft Binder Syndrome Alternate • 3M/Scotch 175 did respond to • Cleaning, • Removing all stationary guides/heads except play head, and • Reduced tension • Sony PR-150 did not respond to this at room temperature Richard L. Hess ARSC Milwaukee 2007-05-04

  22. Sticky shed syndrome (SSS)  • Back-coated mastering tapes • The two coatings appear to interact • Leaves hard-to-remove debris • The layers sometimes adhere to each other (blocking / pinning) • Therefore, use caution when evaluating the previous technique with these tapes Richard L. Hess ARSC Milwaukee 2007-05-04

  23. Sticky shed syndrome (SSS) • Responds to baking • Tapes NOT “as good as new” • Multiple baking may degrade tape • “Last Ditch Effort” to recover content • May be getting worse with time • Baking does not re-link the chains but temporarily raises the Tg and appears to reduce the pinning. Richard L. Hess ARSC Milwaukee 2007-05-04

  24. Sticky shed syndrome (SSS) • Ric Bradshaw, IBM/Challenger tape hypothesizes, “All of the back coatings are far more binder rich than the magnetic coatings and their modulus is half that of the magnetic coatings due to the very poor reinforcement of carbon black. “I believe what happens is that the back coating and magnetic coating are compressed into a high pressure contact during storage, and since the binders in both are essentially the same, they intermix and entangle over time such that when you pull them apart some of the magnetic coating and some of the back coating are transferred to each other as they separate—pull-outs. “This deposit is above the normal surface and is clipped off onto the head during tape motion. The frictional heating is enough to make the debris ‘melt’ to the head and it can be very difficult to clean off.” Richard L. Hess ARSC Milwaukee 2007-05-04

  25. Pinning / Blocking  • Binder adheres to next layer’s back • Binder/oxide is ripped out • Increases with higher tension, usually near hub • Anecdotal evidence supports: • Cold soak* • Slow unwinding • Rehumidification • May happen with SSS tapes • A month at +4°C with silica gel packet Richard L. Hess ARSC Milwaukee 2007-05-04

  26. Binder-base adhesion failure  • Binder/oxide delaminates from base film • Not widespread • May affect Ferro-Chrome (Type III) cassettes more than other tapes • May respond to cold soaking Richard L. Hess ARSC Milwaukee 2007-05-04

  27. Factors influencing degradation • Tape formulation / component selection • Component degradation / failure • Manufacturing defects / tolerances • Storage conditions • Playback without proper conditioning • Playback on defective equipment Richard L. Hess ARSC Milwaukee 2007-05-04

  28. Prioritization of preservation • Assessment tools such as FACETby Mike Casey at Indiana University • Identifying at-risk tape types/batches • Running changes make this difficult • Tapes can have multiple formulations during their run • Rank importance as well as risk Richard L. Hess ARSC Milwaukee 2007-05-04

  29. Anticipated lifetimes • Manufacturer design life: 10–20 years • Oldest tapes are approaching 60 years • Some 30-year-old tapes difficult to play • Player obsolescence is now • Studer is supporting the A807 thru 2010 • Only available reel player: Otari 5050 • No new top-of-the-line cassette players Richard L. Hess ARSC Milwaukee 2007-05-04

  30. Prediction of life • Low reliability of tape life prediction • Life can be batch-specific • Cannot rely on tape box to ID tape • Most tapes are now past design life • Past storage history • May adversely affect life • Usually unknown and unknowable Richard L. Hess ARSC Milwaukee 2007-05-04

  31. Prediction of life: Measurement • Bradshaw is thinking that Tg might be the degradation indicator we wish for • It is not trivial to measure the mechanical properties of the mag coating off the base film! • A “pool test kit” is considered unlikely Richard L. Hess ARSC Milwaukee 2007-05-04

  32. Ongoing research • Prestospace in Europe • Working to define the preservation factory • Looking for markers to prioritize assets • Canadian Conservation Institute • Has evaluated optical media • Is planning on revisiting freezing of tape • Library of Congress • Major upcoming initiatives Richard L. Hess ARSC Milwaukee 2007-05-04

  33. What to do ? • Optimize storage conditions • Prioritize copying • Copy (aka reformat) • Store multiple copies • Use geographically diverse repositories • Use two different, unrelated media • Develop a media evaluation and refresh plan for copies and stick to it Richard L. Hess ARSC Milwaukee 2007-05-04

  34. When ? • Now • If you wish to preserve it, you must start the program now • Not all tapes are failing, but do you know which ones are? • Don’t delay starting in earnest • Do it now … now… now… now Richard L. Hess ARSC Milwaukee 2007-05-04

  35. When ? Now Richard L. Hess ARSC Milwaukee 2007-05-04

  36. GOOD Files CDs What is in typical archives? BAD Reels Records UGLY DATs Cassettes PCM-F1 Minidisc Richard L. Hess ARSC Milwaukee 2007-05-04

  37. The ugly • DAT is dead • PCM F-1 is petrified • Cassettes are a carcass • MD is moribund • Don’t assume any of these formats will be playable in 10-20 years • Transfer NOW! Richard L. Hess ARSC Milwaukee 2007-05-04

  38. The bad • Records are what they are • Still playable • Most manufactured records are not decaying • Many original lacquers are at great risk • Tapes are decaying • Machine obsolescence • Operator obsolescence • Tape degradation Richard L. Hess ARSC Milwaukee 2007-05-04

  39. The good • CDs should be playable for 50+ years • Disk lifetime probably greater for gold phthalocyanine dye CDs (MAM-A) • Fragile • Easily cloned • Supports “shelf storage” model • Limited to 16 bit 44.1 ks/s Richard L. Hess ARSC Milwaukee 2007-05-04

  40. The better • IT Infrastructure • Move from shelf storage to file storage • Audio files are just another file that needs to be stored, backed up, migrated, and returned to the user • Automatic backups • Little manual intervention • Management required Richard L. Hess ARSC Milwaukee 2007-05-04

  41. Topology • Varied technologies • Spinning Disk • LTO-3 tape • Metadata • Rich index of what is in archive Richard L. Hess ARSC Milwaukee 2007-05-04

  42. Security • Multiple disk copies • Multiple tape copies • Off-site storage • Don’t forget storage on different plates, away from faults Richard L. Hess ARSC Milwaukee 2007-05-04

  43. What archive format? • Broadcast Wave • Almost everything can use WAV files • It will survive • EBU has found it useful • Eliminates confusion • 1 TB holds about 1,000 channel hours of 96/24 PCM WAV files Richard L. Hess ARSC Milwaukee 2007-05-04

  44. What about other formats? • Don’t try and mix formats, but multiple bit/sample rates may be acceptable • Down convert for delivery • Convert to the archive format if other formats are ingested, don’t rely on long-term codec availability Richard L. Hess ARSC Milwaukee 2007-05-04

  45. Storage overview • Archival storage must be… • Understood • Funded • Designed • Organized • Populated • Managed in perpetuity Richard L. Hess ARSC Milwaukee 2007-05-04

  46. Storage management • Don’t risk losing audio material • Don’t trust dedicated formats long term • Nothing is certain but change • IT data loss rarely happens • IT migrates for long term storage • Data management is well understood Richard L. Hess ARSC Milwaukee 2007-05-04

  47. Summary • If the content matters to you, do not rely on old tape. • New data tape is fine, as long as there is a plan to refresh it over time. • Just because you can’t play the tape doesn’t mean it’s not recoverable. • Tapes are not getting better with age. Richard L. Hess ARSC Milwaukee 2007-05-04

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