Most chest-type, consumer freezers, available in the U.S. at least, are NOT the frost-free type.? Only one manufacturer makes a frost-free type and it's more expensive than a non frost-free type.? Besides, I agree with Tom Strang; the defrost cycle simply stresses the critters and eggs even more.?
Most small museums can purchase a chest-type freezer plus a Radio Shack digital, remote thermometer very economically, i.e. a 19.7 cu ft Frigidaire Commercial Chest Freezer?costs $748 U.S.? It's 61 1/4" wide, by 35" high, by 29" deep.? It will maintain -25 degrees F. and comes w/ wire baskets, which will keep the materials off the floor of the freezer.? That size will accomodate most of the kinds of infested materials found in collections. Tom Parker -----Original Message----- From: [email protected] To: [email protected] Sent: Thu, 29 Jan 2009 5:14 pm Subject: Re: call for freezer specifications 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. ----------------------------------------------------------- Hi all, I will mention that the point on 'frost free' should not be applied so heavily for the following reasons: 1)The defrost 'warming' cycles (the ones I measure don't allow any thawing) are relatively short duration spaced out through the exposure time, and the general response time of bagged materials commonly 'frozen' is comparatively longer than the warming phase, often much longer, so only the thinnest of objects would warm and chill in phase with the cycle. And these we commonly bag and box up for physical protection or because we have a lot of them to do at once. 2)Which is to say, the target insects will generally be kept cold though the cycle by the cooling or cold object (thermal buffering) and will experience the lowest temperatures the freezer can offer. They will have been immobilized early in the cooling. 3)Household freezers are commonly 'frost free' so you will unnecessarily restrict the pool of useful devices in your readership, many museums get by fine with this form of device. 4)Frost free operation is designed to keep freezers running at optimal low temperature without maintenance shutdowns (for chipping the ice off the coils with a knife to void the warranty and find last summer's Popsicle you saved for later). 5)The objects are bagged anyway so the warming cycle will not deposit condensing vapour onto the object. 6)If you give credence to the need for 'multiple freezings', you get them for free (for thin objects). To test what I say, just put the naked bugs in a vial (the thinnest object of all) in the freezer and follow the guideline you can derive from the CF8(2) article I wrote. Frost free or not, the main point here is to ensure efficacy and avoid harm to the objects. While a manufacturer product selection guide is a pragmatic item, t he guide should emphasize the more timeless features which have proved useful in practice so people can know the minimal features to get or trade off against cost. As a footnote, A.M. Read has the credit of starting it all with refrigeration in the late 1800's, everyone else followed his lead. see: L.O. Howard. 1896. Some temperture effects on household insects. Pp. 13-17 in Proc. 8th Ann. Meeting of the Association of Economic Entomologists, USDA, Div. Entom. Bulletin 6-New Series, Govt. Printing Office, Washington DC. Tom Strang Senior Conservation Scientist Canadian Conservation Institute Canadian Heritage/Patrimoine Canadien Heritage Ottawa, Canada ------------------------------------------------------------- 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]
