There are numerous reasons why tapes may become unplayable. Many are physically obvious; such as:
The Dog tried to eat the cassette ........ and almost succeeded. (Yes.. it happens...)
Goat ate the cassette and DID succeed !
Our clever 3 year old figured out a way to take an entire jelly sandwich & MAKE it fit INSIDE the cassette. Since the sandwich is often larger than the cassette, this actually requires some fairly advanced understanding of 3 dimensional geometry & packaging concepts. You might have given birth to a true genius !
Spills of any sort.... milk & beer however, appear to be the most popular. Milk the result again of 3 year olds, and beer the result of adults often acting like 3 year olds !
Cassette was driven over by pickup truck. (...... just when we thought we saw it all..)
Cassette left in shirt pocket and went through all the washing machine cycles - including the final "Spin-Dry". (at least we won't have to clean it !)
Other reasons are not so obvious..
Tape Stiction - Sticky Tape - exposure to humidity
Recorded on mis-aligned VCR recording equipment - Faulty Tape Alignment
Recorded on machine with worn pinch roller
Dirty video heads when originally recorded
Long term exposure to magnetic fields
Exposure to heat. Even low levels that exceed the curie point of the tape can begin to erase it.
Most damaged audio or video media can either be fully recovered or at least partially recovered & improved on.
However, due to the numerous variables involved, there can never be any guarantees as to the amount of information recovered.
The effects of hydrolysis over great enough period of time, can 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 was the only recording
of a wedding .
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 in Maine come spring, 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. 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 by reducing friction, just long enough for the transfer to be made.
Tapes exhibiting signs of oxide shedding without being properly prepared, should never be burnished. Unless the binder can be re-stabilized, the oxide layer on these tapes is extremely fragile and the least amount of force can tear it completely 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 - or the machine transport gets rapidly "gummed up" by the residue, it's sadly far too late... Instead of a successful recovery, it's then the "All the Kings' Horses, and all the Kings' Men" scenario, as that tape will never play Video Again.....
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 stage 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, there is no chance of recovery in those affected areas. The tape & all it contains, is "history"......
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 a week at most. 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 but have not yet progressed to the Oxide Shedding or Delamination stages !
The main problem with videotape is simply bad chemistry. This is really not a careless design flaw, but simply the the nature of the best technology yet available. 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 wreak havoc with it, causing the urethane particles in the coating to react with water infiltration (a process known as hydrolysis), break free, and then migrate to the surface of the tape. The next time the tape is played, the oxide particles, no longer bound by the binder, peel or flake off, taking with them all evidence of anything previously recorded. The first symptom is clogged video heads.
Though all tape formulations are susceptible to the phenomenon, tapes manufactured between 1965 and 1985 are especially vulnerable to the "Sticky Tape Syndrome", where the tape turns in to a "sticky - gooey - mess" (not the exact scientific term, but nonetheless, an accurate descriptor...). The only hope of video recovery/restoration, is to literally attempt to bake out the moisture and thus harden & stabilize the binder....
Tape Baking works, by baking out the moisture. The two most positive effects of tape baking is that it not only reduces the stickiness, but also hardens up the binder. Bad analogy: but sort of re-manufacturing the tape "on the fly" ....... Though the binder stickiness is reduced & the binder hardened by the process, it still remains porous and weakened. Thus the effects of baking are only temporary , offering a small "window of opportunity" to effect a successful transfer.
The tape is slowly baked in a temperature controlled electric convection oven at exactly 122 deg f (± 1/2 deg f) for a time determined by the mass of the tape and amount of moisture absorbed. Again, the procedure is not a permanent fix and the positive effects of baking are often short lived, ranging from a few days to a couple of months before the effects of hydrolysis become apparent again. But the technique often allows a "window of opportunity" where a successful recovery is now possible.
Just as an aside; we are often asked the equipment we use to bake magnetic tape media. The lab oven we use is a "Blue M" DC-256 configured with an optional Type J temperature controller. Though there are other laboratory ovens that also perfectly "fit the bill", the DC-256 in this configuration offers dead accurate temperature controls, timer, alarm set points, NTE safety limit, and a generous 25x20x20 stainless steel interior, that allows the baking of many tapes at once. Like "Chocolate and Vanilla" - each outfit no doubt has their personal preferences, but when it comes to Lab Ovens: this is ours.
What makes a lab oven so critical to the process, is it's ability to precisely and smoothly ramp up to temperature without overshooting, and then hold a consistent 122 deg F ± ½ deg., and then smoothly ramp down to ambient at completion of the cycle, thus allowing enough time for the tape to cool evenly. No kitchen oven designed for cooking (even the latest models with digital controls) affords such precise process control, regardless of the thermal loading, moisture content and thermal mass of the tapes. Consistent repeatable success will require the use of a true lab oven, if one ever hopes to achieve consistent results.
With that said, some folks have reported success in using home food dehydrators and others even using a cardboard box and a light bulb to serve as a heat source. Such drying "equipment" is not exactly in the same "league" so to speak, nor should it take much imagination to figure out that consistent results can rarely if ever be achieved employing such techniques... Yet, a cardboard box and light bulb is far less expensive than a commercial lab oven...... and if one has only a few tapes requiring baking, then might be worth some experimentation. As a side note: tapes can be re-baked as many times as necessary without any risk of damage. Temperatures not far below 122 deg f, will result in substantial increased baking times (or nothing much happening at all) and temps above 143 deg f, run the risk of exceeding the Curie Point. 122 deg F is the accepted safe "magic number", but more importantly is that whatever temperature you opt to bake at, holding the temperature consistent with adequate airflow to continuously purge the chamber of moisture is critical if one ever expects to achieve 100% success each and every baking run...
NEVER - EVER - NEVER use your kitchen electric oven used for cooking/baking or broiling food, for baking tapes.
No electric oven (even the latest digital types) offer the necessary accurate temperature control required. In fact; "make & break" thermostats often result in chamber temperatures that can swing widely, to as much as ± 70 degrees or more for short periods, while the heating elements kick in and then "idle" til the ovens cools sufficiently, at which time they "kick in" again at full power & the process repeated... Even with the newer digital models, short transients in chamber temperatures will pose problems. - Though much better in terms of temperature stability, since most employ a thermocouple to actually measure the chamber temperature, ovens designed for cooking/broiling/baking, still do not require nor have the precise temp controls of a true lab oven. None I'm aware of, have a ramping function to bring the chamber smoothly and precisely to operating temperature without overshooting the set point, nor is holding the temp within ½ degree necessary for cooking.... No "Big Deal" when doing a roast, as the wide temp swings from the temperature peaks to the troughs, average out..... Just fine for a Thanksgiving Turkey or roasting an 8 lbs rack of beef/ham, as those short temperature spikes encountered as the heating elements cycle on and off, don't account for anything of consequence (the thermal mass of the meat itself, averages out the BTU's added to the system).
Magnetic media is far less forgiving... Exceed the "Curie Point" of the tape for even a short period however (typically 144 deg F for most tape formulations) , and magnetic media will begin to be erased ... not only that, but the outside edges of the tape will naturally heat or cool much faster than the inside center of the tape, often resulting in scalloping of the tape... Thus It is critical that one does not place a tape into a 122 deg pre-heated oven for that reason. Instead, the tape should be placed in the lab oven at ambient temperature and then slowly and smoothly the oven is ramped up to the Process Value (PV) temp over at least a 1 hour period.
There are other concerns such as mass of the tapes themselves to be considered, moisture content, and how one determines and programs the ramping functions of the controller commensurate with the media to be baked. Put another way: A tiny MiniDV tape for example, will require a baking cycle quite different from a 12 inch reel of 1" tape weighing 16 lbs., or even a VHS tape for that matter.
In short: Wish as you might: But when the precision of a Lab Oven is called for, nothing else other than a Laboratory Oven will do, if repeatable consistency is something more than just a passing thought.
Should baking & re-lubing 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 & spool, but none come quickly to mind.....)
Anyways, should "Sticky Tape" be encountered, immediately stop the machine and eject or remove the tape. Do not even attempt to rewind it. To proceed further runs the risk of l not only permanently ruining the tape, but will most likely lead to a severe jam requiring disassembly of the machine to remove the sticky tangled mess as well as another hour spent cleaning up the sticky residue from the tape path and pinch roller.
NOTE: Please do not construe this as a scare tactic (despite the graphic), but rather to grab attention to make certain you read this. Chances of your video tape being host to a deadly mold strain, is extremely remote. You are probably far more likely to die in a car crash in a drive to the local supermarket, than you're being "done in" by your family video tape. The vast majority of moulds are benign and even for people with demonstrated sensitivity to mold spores, exposure to most strains amounts to little more than some mild discomfort at best.
However, with that said, there are a few very rare strains and the embedded viruses they contain, that can be nothing short of DEADLY under the right conditions. - such as those exposed with compromised immune systems... Dried spores can easily be dislodged in the cleaning process and become airborne, making inhalation possible. (Translation: This might NOT be a good thing for your longevity or general well being)....
Thus always wear impermeable gloves and an approved Bio mask at the very minimum. DO NOT re-use the gloves and dispose of them properly. Replace mask filter elements according to the manufacturers recommendations. (Note: Should be a penetrating glimpse of the obvious, but a 99 cent workshop dust mask nor even a mask designed for pesticide application, is NOT the same as a positive pressure Bio Mask running off a remote air compressor where clean air is always being supplied under positive pressure from a remote outside location).
The risk is probably no morethan in deciding to drive to the supermarket in the family car with the kids - yet nevertheless, the risk is not zero. Since no matter what warnings we place here, we absolutely know that some of you will be inclined to attempt it yourself. For those so inclined to accept the risks, please consider at least following the minimal guidelines....
NEVER - EVER no matter how slim the chances, attempt to clean moldy tapes inside confined living quarters where there are either humans or pets - and ESPECIALLY near ANY food sources. Make certain you clean them outside.....
Be especially cautious about black colored mold.
if there is ANY DOUBT WHATSOEVER in what you're dealing with, then contact a KNOWLEDGEABLE health professional before proceeding. (With emphasis on the word: "knowledgeable") Unless positively identified (often an expensive endeavor), treat all molds as a potentially serious health risk.
Most professional commercial tape cleaners employ a sapphire or ruby blade to break up the surface debris and burnish (scrape) the surface smooth & clean. Perhaps yet another bad analogy, but somewhat akin to a snowplow to remove the heavy "debris" of snow from a roadway. The ruby or sapphire blades are effective on new tapes (ie: smooth paved roads if you will), but can totally trash an older tape with a binder just ready to delaminate. Like trying to plow snow from soft muddy driveway, the blade digs in and tears up surface. Thus the razor sharp scraper blade is the final blow and can peel the now aged softened binder right off the substrate. Never attempt to burnish a tape with any signs of mould if the binder is weak. The ruby/sapphire blade will scrape away not only the mould, but sadly the binder as well. Then to add to the misery, mould spores can be thrown into the air where they can be inhaled. If not yet evident; removing mold requires specialized equipment and techniques. Before sending a vintage tape in for professional mold removal, make certain they have experience in handling such tapes.
In the case of just general cleaning where mold is not evident, most tapes we receive require but a single cleaning pass. Every so often, one will show up exhibiting severe mould growth, dust/grime, hexadecanoic acid deposits or any combination thereof. These are easy to spot, as they look like they might have just been fished out of a dumpster... (sadly, this isn't an exaggeration). Naturally, these tapes will require more than one cleaning pass, often using different specialized cleaning techniques if the mold is moderate to severe, which is an additional charge.
Note: There are well over 1,000 different mold strains currently identified , many of which have yet to be categorized or even classified as to their health risks.
So Be Careful.... (the voice of experience speaks) - - - yet another lesson learned the "hard way" several decades ago..... I won't elaborate; only to say it was a "memorable experience".... and one I care not to repeat.....
Even tapes that aren't "gooey" from the effects of hydrolysis, can still stick and bind to the head drum simply from lack of adequate lubrication. The resulting stickiness here is quite different from that due to the effects of hydrolysis. The Binder Layer of virtually all magnetic audio and video tapes were impregnated with a lubricating agent when the tapes were manufactured. This lubricating agent serves to reduce friction and minimize wear.
This lubrication is lost over time, partly due to the tapes' aging process, but also a small amount is "scraped off" each time the tape is played. Thus tapes that don't suffer from the effects of hydrolysis resulting in the dreaded "Sticky Tape Syndrome" or tapes that have been successfully baked, can still bind on the head drum simply from lack of adequate tape lubrication. Tapes that suffer the most from this effect are notably the older reel to reel tapes, though any tape older than 15 years is susceptible. Re-lubrication of the the tape involves a controlled reapplication of the lubricating agent to replace that which was lost, allowing the tape to glide smoothly over the head drum again.
In the case of weakened binders, the reduced friction reduces the effects of oxide shedding by the tape now "gliding" more freely over weakened areas.
We often get calls from folks whose tapes have been submerged in flood waters.
Typical flood damaged tapes as received.
In the case of flood damaged tapes, time is of the essence in getting them properly cleaned before irreparable damage ensues from possible contaminants in the water.
Although we have recovered flood damaged tapes up to 2 years after exposure, this was one of those exceptions where the "Video Gods" were in one of their more rare benevolent moods. Ideally, recovery procedures should be initiated as soon as possible after exposure - preferably within several days. The longer the tape is exposed to the inherent contaminants contained in the waters, the greater will be the risk of permanent damage.
Naturally, folks that have lost their homes have many more immediate pressing problems, so understandably, it's not unusual for us to receive tapes up to a month or more after exposure.
Though contrary to most people's natural instincts, tapes should not be allowed to air dry or left in the sun to dry, as the slow uneven drying often results in physical distortion of the tape, making playback unstable due to constant tracking errors, or in some cases, recovery impossible. The proper drying process is a critical step and must be done in a tightly controlled laboratory oven.
If the tapes have dried out, all may not be lost, but chances of a clean recovery are greatly diminished.
For tapes that are still wet or damp inside, the first on-site step you should take is to VERY GENTLY flush out what you can ..... Gently swirling them in a bucket of clean water is about the most "force" you want to use....
First of all, make certain the water you use to flush the tapes with, contains no chlorine, as is often found in most treated municipal water supplies. Rain water, well water or distilled water is free of chlorine & safe to use for general flushing out of the cassette shell. (The reason one must be certain the water is chlorine free, is that chlorine is an oxidizer that reacts with many organic materials as well as the metal particles in the binder.)
Before you begin, keep in mind the following:
DO NOT blast them with a hose, as the tape is especially fragile when wet. Don't attempt to remove it all, as without specialized equipment and cleaning techniques, you will be lucky to get even half of it, and attempting to do so risks damaging the very fragile tape... Remember; at this stage, you're only trying to dilute the heaviest of the contaminants including oils and solvents that were possibly in the flood waters. If on-site flushing is impractical as is often the case, don't panic.... it can be skipped if no other option exists.
Begin by submerging the tapes in a bucket of clean water (preferably distilled water if available) and keep them cool until they can be packed for shipment, making sure the shells completely fill with clean water. Doing so obviously keeps them from drying out, but also serves to further dilute whatever contaminants are still trapped inside. If worse comes to worse and no clean water is available, then dirty water will have to suffice until clean water becomes available - but make certain there is not the least hint of oils, solvents or chlorine ! In other words KEEP THEM WET - DO NOT LET THEM DRY ! - even if it means having to re-submerge them in murky water if there is absolutely NO other immediate option. Be sure to use enough water to completely submerge the tapes. Solvents, gas and oils if present, will float to the surface and you want the tapes below the floating layer of effluents. If in the northern latitudes, DO NOT permit them to freeze while still wet. As soon as possible, contact us for further more detailed instructions.
Cleaning tapes submerged in flood waters requires more additional steps, but the above is the first easy step the homeowner can perform without requiring any special equipment or cleaning solutions and specialized techniques..
(Keeping them submerged and cool, slows any mold growth, further dilutes any contaminants and obviously keeps them from drying unevenly which can lead to tape distortion. Once allowed to improperly dry, the tapes may physically distort, and no amount of re-soaking will return them to their prior state)
Latent moisture makes for an excellent breeding ground for molds and mildew which require removal. Time is also of the essence here as well, as once the moulds grow into the binder, they sometimes become impossible to remove without destroying the tape in the process. Flood waters normally contain great quantities of organic materials and mould growth can be quite rapid - especially in warm tropical climates.
Flood waters also may contain, mud, silt, grime, both organic & in-organic materials, oils, gasoline, lubricants, solvents and a host of other contaminants which all must be removed. Mud and silt have an amazing propensity for finding their way even inside cassettes even stored in protective covers.
Removal of the tape from the cassette housing is required for proper cleaning and adequate air circulation when baked. Drilling drainage holes in the reel spindles is also sometimes required.
Some shells are thermally welded or the securing screws and internal components (springs, guide pins etc) have turned to "rust", necessitating having to re-shell the tape in a new housing. In most cases, the old shells are re-useable.
Mud & silt even infiltrates the
cassette shells, which necessitates removal of the tape and literally
flushing out the heavy muck as the first step. Though it appears hopeless,
this tape and the 42 others in similar condition were recoverable.
These VHS-C tapes were likewise filled with mud. They're now washed & ready for the oven. After baking, they're put back in their shells and then run through the final cleaning stage. Finally they're placed in a vcr and "with fingers crossed", the transfer is made.
It may seem like a penetrating glimpse of the obvious, but never store media in basements - especially in cardboard boxes that turn to "mush" when wet. Even on the off chance the flood waters were clean, the dissolved cardboard fibers make for a real mess.
Due to the wide variations in types of damage, (gas, oils or solvents present in the water etc etc) it's impossible to predict the outcome of tape restoration efforts or even the costs for restoration. Some water damaged tapes need only a simple cleaning and baking, while most others require much more, such as removal of the tape from the cassette shells - especially if the waters were contaminated. There are so many variables, it's simply impossible to predict. Thus the best insurance beforehand, is to get them transferred and save copies in separate locations.
Successful recovery depends a lot on immediate attention as well as the type of water damage (ie: How many and what type of contaminants were in the flood waters). There are a lot of variables & unknowns and successful recovery is not always possible or guaranteed.
The process does not make the tapes immortal nor will it renew them to "Factory New !" condition. The positive effects of baking after submersion are normally short lived (lasting anywhere's from several days to a month or two). However, this allows a window of opportunity for playback to effect transfer to a new medium.
Though the master tapes are returned, we strongly recommend they never be played again. Note that we often remove & discard the internal spring locking mechanisms and sometimes other non-critical components that often have become rusted and prone to jamming. Note also that the adhesive paper labels rarely survive the cleaning process, so be sure to note any labeling before sending the tapes in.....
All of our efforts are spent cleaning and processing the all important tape. As such, we spend very little time in trying to make the old shells appear "as new". We clean those only to the point that affords reliable playback. In cases where there is too much internal damage to the shell & it's components, we will then re-shell the tape.
In the case of flood damaged recovery work, all of our efforts are targeted towards performing the recovery. As such, we do not perform any editing or spanning of tapes across DVD's...... Final labeling is by reel number, month/year when known and amount transferred.
I cannot emphasize enough: TIME IS OF THE ESSENCE... Proper cleaning and drying must be done as soon as possible to afford the best chance of full recovery..
1/2 inch, 3/4 & 1 inch tape formats usually have around a 95% successful recovery rate, owing partly to their wider track pitch and lower data densities. These wider tape formats can sustain a fair amount of physical abuse, since any given area of oxide damage represents a much smaller picture area. Smaller format and metal particle tapes (8mm, Hi8 D8, MiniDV for example) generally have about a 70% chance of full recovery. The high data densities of these formats requires precise alignment and any damage represents a much larger image/data area. In other words, the smaller formats are not nearly as robust or "forgiving" as their older analog counterparts. Although mud and silts oozing out of the cassette shells may appear to make the situation hopeless, in fact, they do not pose much of a problem once properly removed. It's what you don't see that usually causes the serious permanent damage..... 70 to 95% recovery rates in light of all the tapes have been through is quite impressive (even we're still amazed after seeing their condition upon arrival ! ) These percentages however, can take a real "beating" the longer the delay before recovery procedures are initiated. I can't repeat it enough - - - TIME IS OF THE ESSENCE to afford the best chance of a full recovery !
Even so, we are in most cases still able to recover sections of Katrina damaged tapes being uncovered from below the rubble even a year later !
Any amounts of solvents in the water such as gasoline, oils, paint thinners, Acetone, Xylene, Xylol, fuel stabilizers, lacquers, etc etc etc can spell almost instant disaster - even in very small trace concentrations. However, even with heavy concentrations of solvents in the waters, some tapes will survive virtually unscathed, if they were lucky enough to fill quickly with "clean" water & sink rapidly to the bottom, where they are "protected" by remaining below the effluents floating and passing above. There are a lot of unknown variables !
Fire damaged tapes ironically often exhibit many of the problems of Flood Damaged Tapes.
This owes in part to part of the firefighting effort, whereby Firefighters often employ water as the "chemical of choice" to extinguish the fire.
Thus fire damaged tapes often suffer both from the maladies of flood damaged tapes as those of being Fire Damaged.
Aside from the water damage issues discussed earlier, Fire Damaged tapes also almost always suffer from the effects of smoke. Like flood waters, smoke particles may contain numerous organics and inorganics & other contaminants, depending on the source & type of fuel being consumed. Like flood waters, the smoke permeates nearly everything - usually to the tape inside the cassette shell itself. Thus recovery procedures often closely follow those employed in the recovery of flood damaged tapes.
What is different, is almost always the visible damage to the cassette shell itself, which can often appear severe. Although we cannot recover "piles of molten goo", often times the damage to the shells is superficial. What counts is the tape inside and to what degree it was effected. In a sense, (albeit a twisted way of looking at it) is that the more damage the shell exhibits, represents heat or thermal energy that was expended in destroying the cassette shell; leaving sometimes the tape inside somewhat unscathed. Somewhat akin to a plane crash , where the wings were sheared off, the landing gear ripped away and most of the under carriage in ruins. Destruction of the main structure served to absorb the energy, leaving the passenger compartment and what it contained, to survive relatively intact. (albeit: somewhat bruised , battered & perhaps limping - but nevertheless: survived)
So sometimes things things play out much better than one ever could have surmised, based on the preliminary evidence at the "crash scene"..... Such is often the case with Fire Damaged Audio & Video tapes.
The shell is almost always "history" and the tape has to be cracked open much like cracking open a walnut (or eating a lobster as here in Maine). Every shell component is a total loss, yet other than that part of tape that resides behind the flap which is often melted and has to be cut out and spliced, much of the tape often survives, having been protected by it's surrounding shell & outer wraps of the tape itself.
Naturally, the melted parts of the tape have to be cut out and the remaining "good" ends, spliced back together, and then the tape remounted in a new full sized shell.
Obviously once we "crack open" the shells, some tapes will be deemed to be unrecoverable based on what we observe. For those that look like they'll "stand a chance", most after special processing and cleanup will play - albeit with problems and areas of instability..... but in about 60% of the cases, perfectly viewable. (though fair warning: The video will not win any Emmy's based on their "Technical Achievement"). Then occasionally even we'll be surprised and come across others that will play with no problems at all.
The audio being a far simpler signal, in many cases, often survives fully intact unless erased by the Curie Point being exceeded or excessive heat induced edge damage.
It is a time consuming procedure and obviously no guarantees can be made as to how much if anything can be recovered. Generally in the case of numerous tapes to be recovered, we recommend sampling 5 of those most representative of the rest. That usually gives a rough idea of what recovery rate and degree to which successful recovery might be expected.
So common are MiniDV problems, that I suppose it warrants a separate discussion.
MiniDV offers near broadcast image quality to consumers at an affordable price. Most notable is the small tape size that makes compact camcorders a reality. There is a price to be paid for that compactness however.....
The small format results in a LOT of data being "crammed" on to a very small piece of tape "Real Estate". Thus the data density is quite high. With only a 10 micron track pitch, it takes very little in the way of tape path mis-alignment or tape damage/distortion to warrant a tape unplayable. This is usually manifested in the video exhibiting "blocky" video - often described as pixelating - pixelization or mosaic pattern video. Since the audio in the MiniDV format is interleaved with the video, it is also common to experience distorted audio in addition to video breakup.
For reasons unclear, the problems tend to occur far more frequently on the most important video.
Using specialized techniques, we are able in most cases to recover both the audio and video. In the case of wedding photographers or production companies, we have saved many a shoot from having gone "down the drain", & the embarrassment of having to make that dreaded phone call to inform the client that the video is "trash"....
Note: We do not however support the recovery of HD or LP recorded MiniDV tapes..
Often times, a video head may become clogged during the recording phase. Upon playback, a video image is discernable, but appears to have 50% random "snow" mixed in.
Successful Skip Field Recovery depends upon whether it was just one head that was clogged or both of them, as most consumer analog recorders use 2 rotary heads that are switched during the vertical interval to record each field separately. If just one head were clogged while the other remained clog free, we have a modified Framestore TBC that will repeat either the odd or even clean field to "build" a clean frame from a single good field. Since only 1/2 the information is actually recovered, the video will lack some vertical resolution - but even so, still makes a surprisingly good acceptable picture....... - much like the old skip field format.
If it turns out that both heads were clogged (as is sometimes the case) then what you have is there to stay. There's simply no good field of video for us to select from. Note that Skip field recovery only works for the analog formats such as VHS, Beta, 8mm, Hi8, 3/4-Umatic or any format that used a half wrap with two video recording heads and the case for most of the other vintage analog formats. . 1 inch type C used only 1 head that made a full frame sweep, and thus Skip Field Recovery would not be applicable for that format. Because of the way digital data is recorded into sync blocks in the newer digital formats, Skip field recovery is not possible in any of the newer digital formats.
For a better understanding of interlaced video: fields and frames: Click Here......
Last Modified: May 26, 2011
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