We try to have a shorter freeze-down time – within 24 hours if possible, though it depends greatly on the mass of the freezer load. We run at -33C for a minimum of 72 hours, but usually for closer to 100 hours. We allow natural warm-up to ambient temperatures, which tends to take a minimum of 48 hours, again depending on mass of the load.
The above parameters apply to artifact/specimen materials and all such materials are enclosed in cardboard boxes or plastic bins and/or wrapped in polyethylene. If we are freezing packaging and pallets, the run time might be at the shorter end, and I force the warm-up in stages, as our chamber also has heating capability. That also allows the use of a heat cycle on non-artifact materials, which saves time over the freezing. Regards, Helen Helen Coxon Senior Conservator, Preventive Conservation Royal Ontario Museum 416-586-5897 From: 'Adrian Doyle' via MuseumPests <pestlist@googlegroups.com> Sent: Tuesday, January 19, 2021 4:15 AM To: pestlist@googlegroups.com Subject: [PestList] Thawing times after freezing [EXTERNAL EMAIL] DO NOT CLICK links or attachments unless you recognize the sender and know the content is safe. Morning folks, we are trying to get some extra freezing done as we have lost time due to the Covid epedemic. Has anyone got any research on thaw times for freezing they are prepared to share? At the moment we have a rather long return to ambient from -35c / -30c primarily to allow the objects to thaw slowly and prevent thermal shock but would like the option to reduce this both in our manual operation and to change our computer settings. Note we do not open the freezer and handle the objects whilst frozen as a precaution due to potential embrittlement. our current programme is this 48 hours to reach -35c (or more if not met) 72 hours at -35c to treat 41 hours to defrost/thaw Any thoughts on this would be appreciated many thanks Adie Adrian M Doyle is currently working from home but is available via e mail on ado...@britishmuseum.org<mailto:ado...@britishmuseum.org> Adrian (Adie ) Doyle Integrated Pest Manager Department of Property and Facilities Management British Museum London UK -- You received this message because you are subscribed to the Google Groups "MuseumPests" group. To unsubscribe from this group and stop receiving emails from it, send an email to pestlist+unsubscr...@googlegroups.com<mailto:pestlist+unsubscr...@googlegroups.com>. To view this discussion on the web visit https://groups.google.com/d/msgid/pestlist/PR1PR02MB4746936BEEC8F03D65C3FF34DDA30%40PR1PR02MB4746.eurprd02.prod.outlook.com<https://groups.google.com/d/msgid/pestlist/PR1PR02MB4746936BEEC8F03D65C3FF34DDA30%40PR1PR02MB4746.eurprd02.prod.outlook.com?utm_medium=email&utm_source=footer>. Following guidance of the Ontario Chief Medical Officer of Health, the ROM is temporarily closed to the public. Visit www.rom.on.ca<https://www.rom.on.ca> for further updates. ________________________________ Suivant les conseils du médecin hygiéniste en chef de l’Ontario, le ROM est temporairement fermé au public. Des mises à jour seront publiées à www.rom.on.ca/fr<https://www.rom.on.ca/fr> -- You received this message because you are subscribed to the Google Groups "MuseumPests" group. To unsubscribe from this group and stop receiving emails from it, send an email to pestlist+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/pestlist/YT1PR01MB2745CC2015F86163F7E6C74E80A30%40YT1PR01MB2745.CANPRD01.PROD.OUTLOOK.COM.
