A very simply way to absorb the tiny amount of moisture inside the "bag" is to place a wad of cotton balls inside the bag along with the object.
Tom Parker -----Original Message----- From: william remsen <[email protected]> To: [email protected] Sent: Mon, 8 Jun 2009 7:17 am Subject: Re: [pestlist] Wrapping infested objects for freezing This is a message from the Pest Management Database List. To post to this list send it as an email to [email protected] To unsubscribe please look at the footer of this email. ----------------------------------------------------------- Dear Pestlist, I agree with the recent discussion concerning the need to seal the "bag" and minimize the air inside. I suggest thinking of this "bag" as a sealed museum case in which one wants to control the environment during at least two major changes -freezing and un-freezing. Potential damage will come from thermal movement, ice crystallization, and chemical actions and staining from condensed water. Thermal movement and wate crystallization damage are basically unavoidable, except for possibly cooling (and thawing) the most fragile things slowly and minimizing the amount of water that can freeze in and around the object. This could argue for dehumidifiying objects (obviously within their specific tolerances) before sealing them. To minimize condensed water, one could also replace the gas inside the "bag" with a dry gas with minimal water vapor to reduce the danger of condensation in the bag. Obviously the smaller the volume of air around the object, the smaller the total amount of water vapor there can be. The "bag' should be kept sealed as it un-frozen to keep exterior condensation off the object. Keep an eye on the temperature and dew point in the environment where the "bag" is thawing. If one controls the temperature, and the air flow and its moisture content, one can limit the possible condensation on the outsid of the "bag" . When in doublt, totally control the air flow (seal it to minimize fresh air bringing in additional moisture) around the "bag" in as small a practical volume of dry air (dehumidified) as possible while raising the temperature slowly to above the dew point. Physics dictates that condensation will occur when the object''s (or the bag surface) temperature is below the dew point. Be prepared to capture and control condensation. One ca n use a small fan to evaporate away the condensation once the environment's temperature is above the freezing termperature. This also warms the object slightly faster. Creative solutions do not have to be costly! Some of this may not be critical for all objects, and it may be adequate to simply seal the bags on cool dry, days in dehumidified environments. Please remember that plastic films still have a degree of permeability and moisture and oxygen will still pass thorugh them over time - like with freezer burn. Therefore, I suggest that frozen objects not be frozen and forgotten about in the freezer, but be properly thawed as soon as it is practical. One can use aluminum foil-faced plastic to minimize perms and extend storage time, but even seals leak a bit. In my experience these condensation issues are also inmportant when introducing toxic or anti-biological gases into sealed plastic containers to dis-infect contaminated objects. The risks of contamination and the importance of preserving the object from harm seem to justify using the measures described even if plastic bag material is not recycled. Pardon me for stating what all of you probably know already. I generally work on large objects - entire historic buildings, and these issues can become rather straight forward at that scale. -Bill Remsen Consulting Historic Preservation Architect [email protected] On 6/4/09, Dee Stubbs-Lee <[email protected]> wrote: > At our museum, the practice is to routinely wrap and freeze most material > coming in from outside the building (there is quite a lot of it as our > exhibitions and collections storage are in separate buildings) in a walk in > freezer unless the items are felt to be at high risk of damage from > freezing. Our collections storage facility, like many, is overcrowded and > infestations could potentially spread quickly -- we feel the risk of > infestation outweighs the risk of damage of freezing most collections > objects. > > I share Alyssa's concern about the wastefulness of using pla stic only once > (we use polyethylene sheeting, sealed with packaging tape), and we do > sometimes reuse larger pieces of plastic for that reason. The idea of using > a reusable freezing container sounds appealing on many levels, however, I > have always been under the impression that it is important to: > > a) eliminate any extra air in the "bag", and > b) seal the "bag" so that it is airtight > > Both of those would be difficult in the case of any reusable see-through > container or bag that I can imagine. > > Any thoughts? > > Dee Stubbs-Lee, CAPC, MA > Conservator, > The New Brunswick Museum > 277 Douglas Avenue > Saint John, New Brunswick > Canada > E2K 1E5 > telephone: (506) 643-2341 > fax: (506) 643-2360 > e-mail: [email protected] > www.nbm-mnb.ca > > -----Original Message----- > From: [email protected] > [mailto:[email protected]]on Behalf Of [email protected] > Sent: June 3, 2009 8:35 PM > To: [email protected] > Subject: Re: [pestlist] Wrapping infested objects for freezing > > > Alyssa - > > You pose a lot of good questions about wrapping before freezing. > > I think the foremost reason from wrapping is to prevent ice crystal > formation on the surface of the object being frozen. Using any kind of > wrap, such as muslin, kraft paper, cotton cloth, etc. will prevent this from > happening. Most use zip-lock type bags, which can be re-used. If something > has been properly frozen, the wrapping will not be "contaminated" and can be > re-used. > > For larger mounts, you may want to consider constructing a framework "box" > with polyethylene stapled to the 5 sides, and a Velcro fastening system for > the final side for putting the mount inside and then sealing it with the > Velcro attached to the perimeter of the polyethylene. This framework can > therefore be used again and again. > > I can't imagine the object being reinfested after being properly frozen as > it sits on a countertop acclimatizing; no institution has that rampant an > infestation which would cau se almost immediate reinfestation. > > Tom Parker > > > -----Original Message----- > From: Becker, Alyssa TPCS <[email protected]> > To: [email protected] > Sent: Wed, 3 Jun 2009 6:17 pm > Subject: [pestlist] Wrapping infested objects for freezing > > > > Hello, > Here at the Royal Saskatchewan Museum I wrap anything to be treated for > insect pest infestation in polyethylene plastic prior to freezing. These > objects are most often natural history specimens (mounts) and textiles or > leather/hide/feathered objects from our Aboriginal History collection. > Lately this practise has come into question - is it not a waste of time and > resources to do this, especially since much of the plastic must be thrown > away to prevent possible cross-contamination? Could the wrapping stage be > eliminated for adsorbent objects in good condition? > My reasons to continue wrapping are listed below. However, I wanted to pose > these questions to the list for thoughts, from a practical point of view, as > to whether wrapping is important, and if so, how and when. Has anyone has > come up with a more environmental alternative? For example, has anyone found > a line of vapour -proof, washable tubs that would do the same job for a > variety of sizes of mounts? > Reasons for wrapping: > 1. To contain infestation while transporting specimen to the freezer > 2. To prevent moisture content changes in the object during freezing, which > could result in dimensional changes and physical damage > 3. To prevent damage from possible freezer failure (water drips/ floods, > debris from ceiling) > 4. To prevent condensation from forming during its acclimatization before > the bag is opened > 5. To prevent (or slow) re-infestation during acclimatization > Your thoughts and ideas on the subject would be most appreciated! > Sincerely, > Alyssa Becker > Conservator > Royal Saskatchewan Museum > 2340 Albert Street > Regina, Saskatchewan S4P 2V7 > P: 306-787-2667 F: 306-787-2645 > [email protected] > > > > > _____ > > Wanna sli m down for summer? Go to America > <http://www.aolhealth.com/diet/weight-loss-program/?ncid=emlcntusheal00000001> > Takes it Off to learn how. > > ------------------------------------------------------------- To send an email to the list, send your msg to [email protected] To unsubscribe from this list send an email to [email protected] and in the body put: "unsubscribe pestlist" Any problems email [email protected]
