#16
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The magnetism on a particle used in a magnetic medium lasts forever. It is a single domain with a permanent magnetic charge. The signal on a recorded magnetic medium, however, depends solely on the pattern of the billions of magnetic particles. Recording rearranges their magnetic (not physical) orientation to a particular pattern. Erasing randomizes their magnetic orientation so that no pattern is evident.
On another subject in this thread, the protective lacquer on any optical disc makes no difference what color it is, as long as it seals the edges of the disc and prevents air or moisture from reaching the mirror layer. Sputtered gold as a mirror layer does not oxidize, so it is superior to silver alloys or aluminum only in case the lacquer is defective and allows sulphur-bearing air to reach the mirror layer. In other words, gold is superior only for CD-R discs that might be damaged or defective. Gold reflects less than silver alloy and must be relatively thick in order not to modulate the reflected laser output. For DVD use, gold is inferior to silver alloys in writable optical discs because the specifications for DVD+/-R were designed for silver alloy. I have never found a DVD+/-R disc with a gold mirror layer to have initial PIE errors lower than about 50, while the best silver alloy DVD discs could have PIE errors in the low single digits. The average expected lifetime of a well recorded DVD+/-R disc is about 52 years according to the most accurate environmental tests done on them. 95% would be readable after 39 years with proper storage. CD-Rs using phthalocyanine dye would be readable in 125 years. The weak point for both discs is the dye used, not the mirror layer. The quotes of 100/300 years of lifetime expectancy for DVD/CD recordable discs are bogus because the testing was too short and used only a single stress factor--heat--instead of the double-stress tests using both heat and humidity. |
#17
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Just like audio tape it will pretty much live indefinitely, or until the material degrades. Audio tapes need to be baked to alleviate the moisture and it does something to the material to allow that one last play to transfer whats on em safley....ive done it to 40-50 year old tapes with no issue...and no quality degradation. There is still wire recorders out there too...with material still on teh wire from 70-80+ years ago!
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#18
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Audio tapes do not need "baking" or any other special treatment unless they used a particular hydroscopic polyurethane in their binder formulations. A good portion of Ampex and Agfa production suffered from this instability, and some 3M production also used the same binder. BASF, Maxell, and TDK tapes do not suffer from the same problem and should never be "baked" prior to playing them.
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#19
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I think the oldest VHs Tapes I Have are a couple from 1978 and 1979. have made copys of them on other vhs tape and dvd-r. Both tapes play back just fine. I use DVD mainly to play them on my laptop.one tape is Elvis in concert. One of the last concerts he did, with the original 1970's commercials. "At GE we never stop inventing the lightbulb"
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#20
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Quote:
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Audiokarma |
#21
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It may very well hurt the tape if the tape is baked and doesn't need it to drive moisture out. It all depends on the particular chemistry the manufacturer used to make the tape. Cross-linking, base pre-treatment, surface treatment, varying lubricants, double-calendering, and a number of other manufacturing techniques may respond differently when a tape is subjected to heat beyond that for which it was intended. Certainly expansion and contraction put extra stresses on the tape pack when it is heated beyond 90 degrees F.
At BASF we put thermo stickers in all our containers shipped during summer months and paid extra to make sure no tapes were subjected to more than 95degrees F. If they were, the shipper paid for the container, and we threw the tape out. |
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