The Ampex patent recommends both 50 and 54 °C (122 and 129 °F) and I try
to hit the middle of that range using the thermocouple.
Having 8 tapes in the dehydrator may increase the length of baking
required, but the 1/2-inch tapes that failed to recover at 24 hours was
one particular batch and I did not know their storage history.
I do find that less than 24 hours is often problematic with tapes I get
in to transfer, so just running 1/4 inch tapes about 24 hours seems safe.
There is a much greater risk from pulling mag coat off if the baking is
under-done (or not done at all) than any damage that the baking at these
temperatures may cause (which, so far, I think is none).
I used to play a bit with the time-temperature ratio, but do not now.
The one time I baked a set of tapes a second time, it did not appear to
be an issue, although others have reported being less lucky.
On 2014-02-24 10:31 AM, Smith, Allison wrote:
> Hello and thanks to everyone who has responded so far to my post -
> I'm intrigued by the dehydrator solution. Richard, could you tell me
> what temperature you are setting the Nesco unit to, when you bake 24
> - 48 hours? Is it the lowest setting? If so, I'm wondering if the
> dehumidification process is less stressful / radical than traditional
> convection oven heating (higher temp for a shorter period of time) -
> letting the tape layers relax into place more naturally/gently? Or,
> does this matter? Anyone done a study?
> For those of you using the dehydrating solution - do you have a
> temperature/time ratio that you generally use, that you would share?
> Will you tell me the model you are using, with the temp/time?
> How have your tapes held up post - dehumidification? Is it similar
> to baking - where you only get a few plays before the tape needs
> processing again? Will they bake again if necessary?
> Thanks so much -
> *********************************************************** Allison
> A. Smith Archivist, Wisconsin Public Radio 821 University Avenue,
> Suite 7151 Madison, WI 53706-1497 P (608) 263-8806 F (608)
> 263-9763 [log in to unmask] It's not true I had nothing on, I had
> the radio on - Marilyn Monroe
> -----Original Message----- From: Association for Recorded Sound
> Discussion List [mailto:[log in to unmask]] On Behalf Of
> Richard L. Hess Sent: Friday, February 21, 2014 04:52 PM To:
> [log in to unmask] Subject: Re: [ARSCLIST] Recommendations -
> Convection ovens for baking tapes
> Hello, Allison,
> Many of us use the American Harvest food dehydrators from Nesco. I
> have had and used the same one for over 10 years and it still checks
> out OK. I would suggest checking the temperature dial from time to
> time with a nice thermocouple thermometer, especially since the
> out-of-factory calibration could be better, but the stability is
> about in a 2 °C window which should be fine. The fast airflow removes
> the moisture and other volatile products, though a white filter over
> the air outlet has never become discoloured in my testing.
> I would, however, recommend using this with outside exhaust in a
> commercial application due to the possibility of someone saying they
> got sick because of it...stranger things have happened.
> I like this as each 10.5-inch reel fits on its own slotted shelf, no
> spacers required.
> The convert-a-tray shelves remove for laying in non-NAB hub reels.
> I have both the older unit with the fan in the base and this one.
> This one is my "moldy" machine which is kept in the garage for tapes
> that I do not want to contaminate my main one with. These URLs may
> get split...
> Also available in gray
> convert-a-tray kits:
> These will take reels up to 12.5 inches in diameter.
> If you have 14-inch reels, the large one takes the tape pack but is
> about 1/4-inch shy for the flanges...
> and the add-a-trays to allow baking 1" tape--these are not adaptable,
> so I cut out the inner screen on four trays, making them just rings.
> I have probably processed over 1000 reels of tapes through my
> various dehydrators and all have worked well. In one month, I ran 114
> 10.5 inch reels of 1/2-inch tape, each tape being baked for 48 hours
> because a 24-hour bake was not enough. One reel was sent back for
> re-baking and ran through four 48-hour cycles and then played
> fine...it was Scotch 226, the others were all Ampex 406, if I recall
> I used the large oven to bake about a dozen instrumentation tapes
> containing seismometer signals of the Mount St. Helens volcanic
> eruption from 1980 and a few 14-inch reel master tapes.
> Obviously, many of the other scientific and production tools
> mentioned are fine, too. These are a very inexpensive, small, and
> fit-almost-anywhere solution that I and others have used with great
> success and no reported damage.
> On 2014-02-21 11:36 AM, Smith, Allison wrote:
>> Hello ARSC members -
>> We are in the market to purchase a new convection oven for baking
>> tapes with sticky shed. While we realize there are other methods
>> for dealing with this issue and are exploring them, we have to work
>> within a budget and timeframe that requires baking.
>> The oven we currently use is not very good at accurately regulating
>> an even temperature, so, we are looking at some of the professional
>> brands, which can get quite expensive. Can anyone recommend what
>> they are using, and let me know the make / model?
> -- Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada 647 479 2800
> http://www.richardhess.com/tape/contact.htm Quality tape transfers --
> even from hard-to-play tapes.
-- Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm Quality tape transfers --
even from hard-to-play tapes.