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Videotape Life Expectancy    Tape Baking   Tape Cleaning 

 

Magnetic Tape Construction

Magnetic tape construction consists of a thin binder layer comprised of iron oxide or metal particles that records the magnetic signal and is supported by a thicker film backing or substrate. The magnetic layer (or top coat) consists of magnetic particles suspended in a polymer binder. The binder holds the magnetic particles in place, and binds them to the substrate layer. The binder layer which also contains the magnetic particles, is the layer that is in contact with the drum and rotating heads.  The top binder coat records and stores the magnetic signals written to it, and its composition partly determines the frequency response, sensitivity, distortion, and inherent signal-to-noise ratio.

The binder also also contains a lubricant as well as carbon black to minimize static buildup that would attract debris. A head cleaning agent is also impregnated into the binder to reduce head clogs... As you might have guessed by now, the binder layer of the tape is the most critical layer, as well as the most complex.

The binder, since it contains the magnetic oxide or metal particles, must be thin enough to allow close proximity to the rotating heads. Thus the binder by itself, hasn't the necessary strength to give the tape durability or dimensional stability. To give the tape strength, the binder is bonded to a thicker substrate. Finally a smooth back coat layer is usually applied to the backside of the substrate. This smooth back coat reduces friction, minimizes static buildup and provides a smooth stable base for the overlying wraps.

Unfortunately, the magnetic oxide/particles, binder and backing are all potential problems...

Degradation of the binder occurs whether or not the tape has ever even been used or recorded on.  Normal humidity in the air seeps in to the binder and weakens it's physical characteristics - a process known as hydrolysis (bad analogy, but much like soaking the labels off of a glass bottle). When this occurs (it's just a matter of time), the binder delaminates from the substrate and turns into (for lack of a better technical term) a gooey sticky mess. The phenomenon is known as "Sticky Tape Syndrome"........    The sticky broken pieces of binder & its' suspended magnetic oxides, clog the heads or literally delaminate and fall off if ignored too long, making playback impossible. The now sticky tape will not slide smoothly over the guide posts and head drum, but will stick - bind and literally audibly squeal in protest. In severe cases it will stick so bad that tape motion is brought to a grinding halt, as it binds up around the head drum or wraps itself in a tangled gooey mess around the capstan and jams up tight..  So high can be the tension that in some cases the video heads can chip from the forces of the pinched tape and sometimes mangled tape, turning your VCR into a glorified  pile of junk.  (wonderful, huh ?)

Closely related to the sticking problem is the lubricating agent impregnated into the binder layer when the tape was manufactured. Over time and repeated plays, that lubrication is slowly lost....... again resulting in excessive friction.

The binder and substrate are also susceptible to breakdown by exposure to heat as well as ultraviolet light. Many older tapes have had a "hard life" !

Being not much more than a glorified long flexible magnet, videotape by its' very nature, is susceptible to stray magnetic fields.  Like any magnet, over a period of time, the magnetic molecules lose their polarity (slowly self demagnetize). This is influenced to a very small degree by earth's magnetic field itself.  More significantly, the tape transport also becomes magnetized over time. Like audio recorders, video recorders should be de-magnetized as part of a standard maintenance program.  Other than in the broadcast industry, no one I know of ever does, and each pass of a videotape in a magnetized vcr does more damage, as the effects are accumulative. Serious damage is quickly done by exposure to much stronger stray fields such as accidentally placing the tape in close proximity to a large speaker which has a strong voice coil magnet. Even properly stored, the tape will slowly demagnetize over a period of years. When this occurs, the signal to noise ratio falls and the video appears noisy with washed out colors, and lacks high frequency detail. 

So even in the best storage environment and never played, the videotape is ultimately doomed.

 

If all this isn't enough, the tape must endure physical punishment

Other than somewhat degraded video quality, tapes less than 5 years old will usually play with little trouble, but a lot depends on the quality of the tape and shell housing, how it was stored, how many times it was previously played, whether it was periodically re-packed & re-tensioned and how gently the vcr handled it. 

Most home Vcr's are hard on tapes. The tape transports are not particularly sophisticated and can easily stretch, scrape and distort the tape. Instead of guidepost roller bearings, most consumer machines have fixed guideposts where the tape just drags over the the posts.   Vcr pinch rollers (the rubber rollers that pinch up against the capstan to pull the tape out of the cassette and thru the transport) don't last forever. A bad pinch roller is a common problem, as no one ever seems to replace them. When the rubber gets old, brittle and distorted, they skew the tape unevenly; forcing it into the upper or lower stops of the guide posts. This curls the video tape and causes extreme wear on the tape edges. Since the control track pulses are usually written towards the outside edge on most vintage formats and the tape is now physically distorted, the servo system begins to mis-track.  The distortion usually isn't uniform and the "auto-trac" functions on new vcr's can't keep up. The end result: the tape is mis-positioned for the next field and the scanning heads aren't scanning down the middle of the video tracks, but instead end up in the guard band. You end up with tracking noise in the video, or in severe cases no video at all if you have a newer model vcr that blanks the video if adequate signal strength is lost. The resulting physical damage to the tape due to a faulty pinch roller, is accumulative.

Cassette table height adjustment is critical. To high or too low, and the tape binds in the entry & exit guideposts resulting in more tape damage. Unfortunately, it's also a common problem.

Sometimes the damage is done by the cassette itself. For years, a well recognized manufacturer's VHS cassettes was notorious for poorly polished entry/exit guide posts in the cassette shell itself.  Several rewinds and they'd leave a nice deep scratch down the length of the tape resulting in a horizontal noise line in the video. Most inexpensive (read: cheap) cassettes also lack highly polished guideposts resulting in excessive wear each time the tape is used.

The environmental conditions in which the tapes are stored plays a major role in the long term dimensional stability of the tape.  It takes very little hardly perceivable warpage or stretching, to wreak havoc on trying to achieve a stable playback. After many years, the dimensional stability of the tapes degrade and the tape starts to deform, depending on the internal stresses on the wraps of tape. These varying stresses are due to uneven moisture absorption/evaporation causing the tape to swell or contract unevenly with the varying trapped humidity between the wraps. Over the years, the tapes "stretch & twist" plus expand & contract, in an attempt to even out the internal stresses. Unfortunately, the deformities are not a constant, which often results in widely swinging tracking errors on playback....  A "penetrating glimpse of the obvious" perhaps, but the longer the pent up forces have to act, the greater will be the deformity. Sadly, many vintage tapes haven't been re-tensioned in over 30 years. This is the reason that it is widely recommended that any tape (either reel or cassette based) be fast-forwarded and rewound at least once every three years to relieve any internally built up stresses on the tape). Some tapes suffer serious dimensional aberrations due to never being re-packed, while others for various esoteric reasons, survive completely unscathed.

Older tapes in particular should never be put into pause, still frame or even slo-motion modes.  If the tape isn't moving, the heads constantly spin over just one area of the tape. Still framing an old tape will often grind right down into the soft weakened binder - destroying that area and inevitably clogging the heads.  If you're going to play an old tape, then keep it moving !    .......     (Somewhat akin to driving in snow I suppose..... if you stop, you'll probably get "stuck" !)

Given all this, it's almost amazing that tapes last as long as they do.......

 

* * * * * * * * * * *

 

Oxide shedding &  delamination of the binder from the substrate, is ultimately the final knock out punch and final death blow to all video tapes. There is no direct cure for either oxide shedding or delamination. We can only hope to minimize the effects in the early stages of either, to affect a transfer.

 

Most tapes from the 60's into the 80's are now starting to suffer from the "Sticky Tape Syndrome" or effects of hydrolysis.  It is usually the predecessor to oxide shedding. As moisture infiltrates into the binder layer, it starts to both weaken & soften the binder, resulting in a sticky tape. If left to "run it's course", Oxide shedding and delamination of the binder will soon follow.  But before it reaches that stage, there is still an excellent chance of recovery.  Recovery consists of baking the tape in an accurate temperature controlled Laboratory oven, that not only rids the binder of  moisture, but also re-stabilizes it  - allowing the tape to play smoothly again  without sticking. Note that the effects of tape baking are short lived - sometimes lasting only 24 hours...

Sticky Tape, Oxide Shedding and/or delamination are all parts of a tape's natural aging process.

 

The following goes into greater detail.....

 

Oxide Shedding

The effects of hydrolysis over great enough period of time, will cause weakening of the binder layer to the point where de-lamination from the substrate occurs. The problem often manifests itself by almost instant head clogs every few seconds, as the least disturbance of the weakened binder by the rotating scanner video heads results in a shedding of the oxide. In severe cases (especially where the tape has been exposed to water & not properly immediately treated), the oxide literally falls off the substrate, making for a horrific mess.

Here the oxide has literally flaked off the substrate. Note the now "transparent" tape and the large flakes of oxide strewn about. Sadly, this  only recording of a wedding is "history".
 

Other causes are exposure to temperatures in excess of 130 deg f or below 5 deg f.  The binder layer and substrate are made of disparate materials with a different coefficients of expansion/contraction.  Excessive and repeated exposure to temperatures outside the norm, may result in almost immediate delamination, resulting in oxide shed. Improperly stored tapes that are damp and then  "fast frozen", will literally tear the binder apart (not unlike our roads here come spring in the Northeast where repeated freezing / re-freezing wreaks havoc).  An asphalt paved road is very similar to a video tape, in the sense that the smooth paved surface corresponds to a tapes' binder layer, and the gravel base is analogous to the tapes' substrate. Not surprisingly, the same environmental processes that delaminate a roads' surface (read: potholes) also results in a damaged video tape.

Oxide shedding is a serious problem, as there is no known technique for repairing the malady (at least without destroying the recording in the process). However, tape baking can make it's effects less pronounced (only if caught in the very early stages before separation is visually evident) by reducing the stickiness and subsequent drag on the tape. Tape re-lubing can also often get a tape with a weakened binder layer to play without shedding off the oxide, just long enough for the transfer to be made.

Tapes exhibiting signs of oxide shedding should never be burnished.  The binder layer on these tapes is extremely fragile and the least amount of force can tear it free. This is a case where often the cure is much worse than the ill.

Once a tape exhibits oxide literally falling off the substrate in either flakes or strips, it's sadly far too late...   "All the Kings' Horses, and all the Kings' Men",  will ever play that Video Again.....

De-Lamination

This topic is closely related to oxide shedding, as well as the effects of hydrolysis and proper environmental storage conditions. In effect, it's the last and final breakdown of the tape.

During manufacture, the binder layer (usually made from a thin coating of polyurethane) is bonded to the substrate layer (usually polyester) thru a process of high temperature and pressure. (No....  the two layers are not "glued" together)......  The high temperature plus high pressure applied, literally forces the molecular bonds of both similar (but still slightly different) polymers together. This results in a strong yet extremely flexible bond... just ideal for the manufacture of both audio and video tape !

Though durable, thin and flexible, the molecular bonds are capable of being broken. Long term exposure to moisture (hydrolysis) or excessively high temperatures (the tape was left out in the sun or in the trunk of a car on a hot summers day) can break the bonds apart. Other common reasons are exposure to any solvent or a damp tape being instantly frozen, as is sometimes the case in the northern latitudes during the frigid winter months... The newly formed ice crystals tear the bonds apart....  When the bonds are broken, the binder layer containing the oxide or metal particles, separates from the substrate. The binder then either flakes off like confetti or may be dislodged in strips.

Once de-lamination has occurred, the tape is "history"...... 

Tape Baking - Video Restoration - Sticky Tape Syndrome


Though the image degrades a varying amount each year, by the time 25 years or so have elapsed, more seriously than the image degradation, is that the video tape is often now unplayable......  owing to mechanical breakdown of the tape itself.  The video tape has sadly arrived at the end of it's useful life. All might not, yet be lost..... it can often be brought back from the grave !  It's not the fountain of youth, but it will stabilize it at least long enough to make a good transfer. After baking, the transfer should be made as soon as possible - generally within 24 hours. This area of the video restoration process is known as Tape Baking and is effective in about 95% of the cases where tapes are experiencing stickiness !

The main problem with videotape is simply bad chemistry. Videotape is made from a base of polyester, which is coated with polyurethane. The coating acts as a binder (alas, it's name), trapping magnetic oxide particles -- the carriers of the magnetically encoded information -- within the tape. The binding system is fragile. High temperatures and humidity can play havoc with it, causing the urethane particles in the coating to react with water infiltration (a process known as hydrolysis), break free, and migrate to the surface of the tape. The next time the tape is played, the oxide particles, no longer bound by the binder, peel off, taking with them all evidence of anything previously recorded.

Tapes manufactured between 1965 and 1985 are especially susceptible to the "Sticky Tape Syndrome", where in addition to the binder delaminating, it also turns in to a "sticky - gooey - mess" (not the scientific term, but nevertheless, an accurate descriptor...).  The only hope of video restoration is to literally attempt to bake out the moisture and thus stabilize the binder....  Sort of re-manufacturing the tape "on the fly" ....... 

The tape is slowly baked in a highly accurate temperature controlled electric convection laboratory oven for a time determined by the mass of the tape. The procedure is not a permanent fix and the positive effects are short lived, ranging from a few days to a couple of months before the effects of hydrolysis become apparent again.  Should that fail, then the sad reality is that you waited too long to have it transferred. The tape and all that it might contain is lost forever, and will simply make a great paperweight.... (There's probably other applications for the tape, but none come quickly to mind.....)

Should "Sticky Tape" be encountered, immediately stop the machine and eject or remove the tape right where it is.  Do not even attempt to rewind it. To proceed further may not only permanently ruin the tape, but will most likely lead to a severe jam requiring disassembly of the machine to remove the sticky tangled mess or even wiping out the video heads.

To read more on Tape Baking:    Click Here

 

Video Tape Storage

Short of destroying them by means or events too horrible to imagine, water and moisture are probably a videotape's worst enemy......  (though young children armed - "locked and loaded" with a jelly sandwich, can do unimaginable damage - far beyond what any hostile invading Army bent on complete & total annihilation could possibly ever hope to achieve !

Above all, keep them dry (referring here to the tapes and not the kids - though coming to think of it; the following would equally apply.....) and store them in low humidity environments if possible. Do not store them against an outside wall, particularly in the northern climates. If possible, avoid storing them in a damp basement for extended periods. (parents - also take note)...  Never leave them in the trunk of a car on a sunny warm day where they can be quickly baked into oblivion.  It doesn't take much heat to slightly distort the plastic shell or ruin the tape contained within (anything over 140 deg will suffice)......  Also keep in mind that flood waters have a nasty habit of ruining video tape if not properly cleaned and properly dried shortly after exposure...  Thus,  keep them high !.

For the maximum longevity, place the tape in a zip lock bag along with a small pouch of silica gel (a desiccant), which will absorb any moisture.  Silica gel is available in some hardware stores and in most craft shops (used to dry flowers) but you can always find them in quantity for much less money on eBay. Quantities of 50 usually run around $9.00 or so but you can purchase silica gel in bulk and make your own bags for much less. 4 lbs is about $15 and will do several hundred tapes at least.  1/2 teaspoon into a small sealed plastic bag punctured with tiny air holes will do nicely...  This won't make your video tape "immortal" but will greatly extend it's shelf life - especially in humid climates.

Keep in mind that silica gel does have a limited capacity. (Don't expect a tablespoon of Silica Gel to hold a gallon of water)...  Every year or so, the packet should be removed and baked separately in an oven at 300 deg for an hour. This will bake the accumulated moisture out the silica gel and make it effective as new !

Note: A penetrating glimpse of the obvious perhaps, but Bake ONLY the packet of silica gel and NOT the valuable tape ! ........   300 degrees will well exceed the Curie Point of the tape (erase it) plus melt the tape/reel, and turn most of what remains into an instant pile of goo ! (our technical term for melted plastic)

Tapes should always be stored either fully rewound or "tails out". Damage and the effects of aging (especially on reel to reel tapes) is most evident towards the very beginning and very end of the tapes. The tape in the middle is protected somewhat more by the outer wraps of tape surrounding it.

  1. Tapes should be stored at 60 to 65 deg f. at 35 to 40% relative humidity.

  2. Never store tapes flat. Store them on end as you would a book. This reduces edge stresses on the tape which can lead to tracking errors later on.

  3. Always store tapes either fully rewound or "tails out"

  4. Keep away from magnetic fields (Do not store in Steel cabinets)

  5. Store in an opaque storage case and keep out of sunlight

  6. If the tape is wrapped in plastic, be sure to use a silica gel desiccant inside the plastic bag.

  7. If you do not use a desiccant such as silica gel, then it's best to unwrap the tape from the plastic and just store it in its' storage box. 
    Without desiccant, all the bag will do is trap the moisture.

  8. Remove any sticky tape such as that used to secure the end of the tape. Over the years, the solvents in the adhesive can migrate throughout the tape

  9. As long as the tape is not sticky or exhibits any mold growth, then every 3 years at most, the tape should be removed & fully fast forwarded to the end and then rewound on a known good deck.
    This re-packs the tape and relieves any built up internal stresses due to uneven moisture absorption. Failure to do so sometimes
    results in stretched or unevenly warped tape, making stable playback without tracking errors unlikely.

Videotape Life Expectancy

Ever since the 1970s, the electronics industry has been trying to persuade everyone to throw out their old cumbersome movie film cameras and buy "state of the art" camcorders to preserve family histories. Compared to film, videotape is cheap, relatively easy to edit, no projector bulbs to burn out......  no problem to set up and watch. The industry claimed that the new video technology would allow them to share with their descendants, priceless documentary footage of births, bar mitzvahs, marriages, and other memories, say 30 or 40 years down the road. Salespeople of the era often claimed they'd last indefinitely !  

Wow !

Here it is coming up on 35 years later, and if you're still heeding that advice, you'll be better advised to start keeping a written diary instead of a video record. It's now widely known and accepted, that the life expectancy of videotapes is much shorter than originally estimated --   All reputable manufacturers rate the life expectancy of video tape from 10 to 12 years. Not one we're aware of claims - much less guarantees a life expectancy greater than 12 years.  Recent technical reports by Sony , Ampex , and Agfa corporations and the Institute of Electrical and Electronics Engineers   suggest that their lives are but a fleeting thing.

In general, just about any high quality branded tape will last at least 5 years while retaining acceptable image quality if properly stored, not too badly abused or simply worn out due to repeated use.  Shortly thereafter, image quality degradation becomes more noticeable, as the tape slowly demagnetizes and physically degrades.  By 10 years, the image quality becomes "noisy - with lack of detail". By 20 years (if you're lucky), the binder begins to show the effects of hydrolysis and the tape is now on borrowed time.  Some tapes go 35 years or more if stored in a controlled low humidity environment, and others breakdown in less than ten before they become completely unplayable. There's no exact way of telling, as there are too many variables. Generally we've found that the wider broadcast tape formats hold up better over time than do the narrower formats. 2 inch quad tapes from the 60's amazingly will usually play with but few problems (after baking & cleaning) while VHS tapes typically give up the ghost much earlier - especially if recorded in any extended play mode.  (Any tape recorded in an extended play mode suffers the greatest no matter what the format).  Metal particle tape seems to hold up the best, though it's too early to tell the long term outcome, as they are a relatively new product. At least that's been our observation.

Lately, we've been noticing an unusually high number of MiniDV tapes exhibiting pixilation of the image. There is a LOT of information crammed onto a small area of tape. The least amount of tape deformation caused by a misaligned machine or improper tape tensions can easily spell disaster. The small tape plus high data densities, results in these formats operating on the "thin edge of success". Another 10 years will tell the tale, but based on our observations so far, the prognosis for long term reliability of the small digital consumer tape formats is questionable.

Unbranded or "bargain" tape is usually no bargain at all.  Life expectancy of inexpensive tape is unpredictable at best.  Consider yourself lucky each time a bargain tape manages to play at all - no matter what it's age....... as for that moment, the video Gods have been merciful.  Tomorrow, things may get back to "normal" and the Gods may not be in such a benevolent mood.

Thus so many variables such as quality of the tape to start with, the precision of the cassette shell, how it was stored, the equipment it was recorded on, how many times it was played, how gently the VTR handled the tape, whether the VTR needed de-magnetization etc etc etc, all greatly affect it's life expectancy. But the outcome is always the same. Videotapes are mortal and generally have a pretty short life.

No matter what the tape, always record in the highest quality mode available. You'll consume more tape, but the information density per square millimeter of tape is much less and thus tolerances are much less critical.  Put another way:  Material recorded in any extended play mode will always be the "first to go"......

Generally , if a tape over 15 years old plays like the day it was recorded (or in some instances, at all) without employing recovery techniques, then consider yourself "Lucky"

Read more on vintage video quality issues, image degradation and video restoration.  Click Here....

 

Flood, Fire, and Mold damaged tapes however pose their own unique problems.  Click on the "Damaged Tapes" navigation button at the bottom of this page to read more on these topics

 

Last Modified: Apr 4, 2008

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