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[OM] Re: OT Darkroom Thermometer

Subject: [OM] Re: OT Darkroom Thermometer
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Sat, 21 Feb 2004 21:05:20 -0500
Check the thermomemter manufacturer's websites such as:
<www.ertco.com/ proper_care_and_use_of_liquid_thermometers.html>
<sargentwelch.com/article.asp?ai=80>
You can easily find many more such sites by searching Google on 
"thermometer" and "separation".

Assuming that your use of the word "spirit" means a non-mercury 
thermometer I quote from one of the above:
---------------------------------------------------
"Separated columns in organic-filled (spirit) thermometers require a 
somewhat different technique in order to be reunited.

The simplest and safest method is to force the liquid down the capillary 
by using a centrifuge, if one is available, with a cup deep enough to 
ensure that the centrifugal force is below the liquid column.

Carefully insert the thermometer, bulb down, in the centrifuge. Have 
some cotton wadding at the bottom of the cup to prevent any damage to 
the bulb. Turn on the centrifuge and in just a few seconds all the 
liquid will be forced past the separation.

If the cup is not deep enough and all the centrifugal force is not below 
the column, the column will split, forcing part of the liquid down. The 
remainder will be forced up, filling the expansion chamber.

If a centrifuge is not available, the column can be reunited by coaxing 
the liquid to run down.

This can be accomplished by holding the thermometer in an upright 
position and gingerly tapping the stem above the separation against the 
palm of your hand. As you gently tap the thermometer, observe the liquid 
above the separation until it breaks away from the wall of the capillary 
and runs down to join the main column. "
---------------------------------------------

I think you might be able to simulate a centrifuge by attaching the 
thermometer to a long, sturdy string and whirling it about your head in 
the fashion of helicopter blades.  Just don't hit any power lines.

Chuck Norcutt

John Wheeler wrote:

> G'day Zuiks,
> 
> Having been inspired by Graham's weekly B&W shots to once again start
> processing in my darkroom (sometimes referred to as the SO's laundry) I've
> discovered that my Paterson thermometer has a problem. The spirit has
> divided itself and a smallish amount has got stuck in the top of the device
> rendering the thing rather inaccurate. 


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