I should add that I wouldn't bake polyester tapes that aren't SSS, especially early-era brown-oxide 
non-backcoat. I am not comfortable with exposing those tapes to that temperature, I'd worry about 
edge curl and warp. I haven't ever tried baking them, so I can't say for sure that this is a 
legitimate worry. My feeling about baking is, it's a remedial measure, not a preventative or SOP 

One more comment on the air-breathing issue. Goran told us some good details about BASF's 
manufacturing methods, how it took a huge chemical conglomerate to have a "closed loop" chemistry 
(100% in-house from raw chemicals to finished magnetic tape). This tells me there are a lot of 
different chemicals in these things and I've never seen an analysis of the gasses coming out of a 
tape-baking oven, what's "steaming" out of the ooze as it dries out and stabilizes. I can say that 
I've never been overcome and rendered sick by baking fumes but who knows 20 years down the road? I'd 
strongly suggest decent venting just because it's common sense. If something doesn't smell good, why 
have it trapped with you in a room? That alone makes a strong case for venting.

Richard is also correct on mold, don't take it lightly. Dry spores in dust on and in the tape, too, 
can be dangerous. Some molds are toxic and some people are very allergic to many types of mold.

-- Tom Fine

----- Original Message ----- 
From: "Tom Fine" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 20, 2012 4:52 PM
Subject: Re: [ARSCLIST] offgasing from baking tapes

>I agree with Richard on all of this. I don't know for a fact that SSS tapes being baked makes for 
>completely breathable air, but I betcha it's less toxic than walking down an urban street. The 
>problem is, they definitely smell a certain way and some people really don't like that odor. I 
>usually bake overnight, with the food dehydrator on top of the stove and the vent hood on, mainly 
>because my wife really doesn't like the odor and I don't find it especially pleasing. Ampex 456 
>smells worse than Scotch 226, to my nose, but that is 100% subjective.
> Richard's last paragraph bears repeating and careful consideration. Only tape exhibiting SSS 
> should be baked. Baking is not a good "precaution" or "preventative measure." Not at all. It ruins 
> older acetate tapes.
> -- Tom Fine
> ----- Original Message ----- 
> From: "Richard L. Hess" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, February 20, 2012 2:15 PM
> Subject: Re: [ARSCLIST] offgasing from baking tapes
>> Hi, Katie,
>> In a commercial environment with the inherent liability issues, I would use an outside-venting 
>> exhaust fan in the area I was doing tape baking--or perhaps a fume hood. I know that's energy 
>> inefficient in Wisconsin winters, so perhaps using outside makeup air or a heat-recovery 
>> ventilation system would be a good choice.
>> I am more concerned about mold and the related toxins than I am about the tape outgassing, though 
>> I can definitely detect the latter when I'm doing baking. I generally bake in a separate 
>> generally unoccupied room, but don't pay particular attention to the exhaust issues.
>> I bake moldy tapes in my garage in a separate dehydrator. I figure any mold that escapes there 
>> will probably find long-lost relatives <sigh>. I also wear a NIOSH-rated respirator when dealing 
>> with mold.
>> One archive I've been corresponding with used a dust mask and I suggested if they were concerned 
>> enough either for health or perception reasons, they should switch to a respirator rather than 
>> just a dust mask.
>> I am not a toxicologist nor doctor nor chemist, so take this as comments of a casual user.
>> Please remember that not all tapes need baking and baking acetate tapes as well as certain other 
>> tapes may do more damage than good.
>> Cheers,
>> Richard
>> On 2012-02-20 1:48 PM, Katie Mullen wrote:
>>> Hello:
>>> We're looking into the particulars of how we would go about setting up a
>>> tape baking program in-house. One thing I have not seen addressed in the
>>> informal discussions about baking or in the literature is whether people
>>> are concerned about exposure to anything potentially harmful (or that would
>>> be regulated under OSHA exposure limits) from off gassing during baking,
>>> and following that, whether anyone uses controls (such as a fume hood) to
>>> mitigate any potential exposures.
>>> A chemist who is studying the degredation of video magnetic media recently
>>> said in response to my query that among other likely products, "Degradation
>>> products of magnetic tape include carbon dioxide, acetaldehyde, vinyl
>>> benzoate, carbon monoxide, methane, and benzaldehyde.  Many of these
>>> compounds are considerably harmful if inhaled, so I would definitely make
>>> an effort to move the baking to a well-ventilated area, or have it
>>> separately ventilated." Beyond the general question posed above about
>>> concern vs. controls, if anyone has actually measured exposure during
>>> baking to the listed components, I would appreciate knowing more about your
>>> results.
>>> Stories from your experiences baking, or particulars about how and where
>>> you do your baking would be much appreciated!
>>> Thank You,
>>> Katie Mullen
>>> Preservation Coordinator,
>>> Library-Archives
>>> Wisconsin Historical Society
>>> 816 State Street
>>> Madison, WI  53706-1482
>>> PH: 608-264-6489
>>> [log in to unmask]
>>> Collecting, Preserving and Sharing Stories Since 1846
>> -- 
>> Richard L. Hess                   email: [log in to unmask]
>> Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
>> Quality tape transfers -- even from hard-to-play tapes.