A degaussing bulk tape eraser should work. Last time I checked they were not cheap. RatShack used to have them for like $30 - when RatShack was halfway decent...

If it's for a paying client, you never re-use a tape.

And unless they actually payed for the tapes, tape over it with something of your own! :D

I don't think you need to pre-record black on a digital tape. That is a holdover from analog days, and primarily from machines that needed lots of pre-roll.

As for re-using tapes, they do stretch over multiple uses, but unless you are using it twenty or thirty times, I wouldn't worry about it. If a tape can't run through the camera four or five times without having problems, then it probably is something you shouldn't be using in the first place.

The $30 bulk erasers never worked worth a damn. As R&D director at Spiratone I was involved in a lot of testing of same. After my tests I concluded that the old shibboleth of "never place your videotape on top of a TV set because the picture tube degausser will erase them," was just that, an old wive's tale. The $30 erasers, even after 10 applications, had no substantial effect on the video. What could be done, was to partially erase the sync track so the playback wouldn't track properly, but with digital tapes that's not an option.

I've never experimented with bulk erasers, but have heard that they harken back to the analog days when such treatments were necessary to lower the noise floor on a re-used tape.

As for re-using tape, sure, tapes can be run through a well-adjusted mechanism for hundreds of times without any ill effects, but then with tape being so cheap, what's the point? Maybe one can make the argument that a known-dropout-free tape is worth MORE than a brand-new but personally untested tape.

As an aside, I recently decided to do a one-camera shoot with the brown Sony HDV tapes (~ $10) rather than the usual blue Sony tapes (~ $3). Imagine my utter shock when I found--Bam! Bam! Bam!--three 1/2 second physical dropouts on the tape within 10 seconds of each other. So much for the touted QC of premium tape. By contrast, the regular blue tapes might give a single dropout in 10 or 20 tapes, but for important stuff I usually have two cameras running. Another thing I will try in a future project is having a parallel backup to laptop. I have a tiny little Sony UX Vaio (about the size of a PDA), and this could be a really cool way of recording.

Dropouts or dropped frames? How do you detect a dropout

Blacking and bulk erasing are an anachronism from the analog tape days. A reel of 2-inch tape would cost a couple of hundred dollars, so yes, they were reused. Our station had a flat-bed tape eraser that would stop your watch if you didn't remove it before using the easer.

Digital tape is pretty difficult to bulk-erase, and as John said, pretty useless.

I'd be really, really leary of re-using DV tape. After 3-5 reuses, I've experienced dropouts due to flaking of the mag material from the substrate. The tape is mechanically very fragile. Every time it runs thru the transport, it gets stressed. After not many iterations it begins to flake off. If you value your footage...don't re-use your tapes.