[Histonet] Question about slide drying/ convection ovens

[Morken, Timothy]

There is a reason to distinguish the type of oven but the terms are used loosely and so cause confusion.

"Convection" is used to describe in nature to describe the natural circulation of heat and can be of "natural" gravity convection in which heat rises, or forced in which some kind of external force spreads the heat "faster" Ie, wind.

Strictly speaking a "Convection Oven" is one that uses a fan to distribute the heat. That is opposed to Conventional Ovens that do not use fans and rely on gravity to distribute heat (heat rises, setting up convection currents).

However, if you look at equipment catalogs you will see terms like "Gravity Convection" and "Forced Air" to distinguish between ovens without and with fans respectively. 

Most ovens in use are "gravity-convection" ovens that rely on the natural rise of heated air to circulate the heat. They don' t use fans.

In contrast is the forced-air convection oven that uses a fan to circulate air and ensure even heating throughout the oven. Forced air can heat/dry a sample faster if the fan is set to circulate air at a faster rate than would happen by natural convection.

So, the moral of the story is to read the description of the oven to find out exactly what kind of oven it really is!


Tim Morken
UCSF Pathology


-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Rene J Buesa
Sent: Monday, January 28, 2013 10:06 AM
To: Natalie Nagy; histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Question about slide drying/ convection ovens

Natalia: 
I just cannot understand the concept of "gravity" convection oven because if you say "gravity" by definition that will mean that the heat will work by gravity and any heated air goes, also by definition, against gravity because any heat air will go UP and not down, hence the "hot air balloons".
Probably the title is just a "catchy" but wrongly selected sales mimic, something "new and different".
Other than that, and going to your question, no I have never used such an oven.
Ovens are of the convection type and in all of them the heating elements are at the bottom and the heated air goes UP.
René J.

From: Natalie Nagy <Nagy_Natalie <@t> holyokehealth.com>
To: histonet <@t> lists.utsouthwestern.edu
Sent: Monday, January 28, 2013 12:40 PM
Subject: [Histonet] Question about slide drying/ convection ovens

Hi everyone,
                  Just have a quick question for all of you out there in histo-land. Have you ever bought or worked with a gravity convection oven (the thermo shandon 20GC), for drying of slides?? If so..how was it? Did it properly dry all of your slides, did it keep temp?? I am thinking about buying one, and wanted some opinions. Or do you all prefer a real forced air slide drying oven?
Thanks in advance,
              
      Natalie Nagy (HT)ASCP
Histology Supervisor
Holyoke Medical Center
Holyoke, MA.



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