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Drying delicate mechanisms


G’day; Adding to my previous post on drying watches etc, here
is a further suggestion; a vacuum desiccator. These are sold
by lab suppliers, but some time after I retired I needed one, and
could no longer borrow one from the lab of course, and not only
is the nearest supplier many miles from me, but I couldn’t afford
one anyway. So I made an ordinary desiccator. Now, you know
those old fashioned glass preserving jars with a glass lid and a
rubber gasket? The lid is hinged with wire, they spring closed
and are completely airtight. Well, I made an aluminium stand, for
watches, weighed crucibles, etc; put it and some indicator gel in
the jar and that’s my desiccator. Very efficient; used it for
about 15 years.

But drying in a vacuum is faster and more efficient. So I
drilled a hole in the glass lid, fitted a rubber bung and a bit
of tube and connected a little gas-tight stopcock to the tube. I
had been using a ‘recycled’ refrigerator pump as a vacuum pump
(pumps down to 28 inches of mercury pressure - plenty) for other
purposes including vacuum distillations, so simply covered the
home made desiccator with wire gauze (in case it decided to
suddenly implode!) and voila! It dries out a watch inside an
hour. I think that the vacuum provided by a bicycle pump with
reversed washer and valve would do it. So long as one worked
hard. But word gets around, and I get calls from local
watch-wearers-in-showers. They generally leave the shower
before calling. Cheers now, –

/ /

/ /
/ /__|\ @John_Burgess2
At sunny Nelson NZ (still!)


Go to the automotive supplies store and ask for suction gun used
for bleeding wet clutches, transmission and differentials. It
looks like a big steel syringe with a tee handle. The
dimensions are 2.5 in dia x 11 in. Pulls a real mean vacuum.

Kelvin Mok (

Home: (780) 463-4099 | Home FAX: (780) 430-7120


I don’t believe that the suction gun and some of the other
devices described will pull an adequate vacuum for drying parts.
The vacuum required (dependent on the ambient temperature) is
29.+ inches of mercury, which is strong enough to collapse a
1/8th" flat steel plate box.

The whole point of using a vacuum is that water boils,
literally, under a sufficient vacuum.

I own several vacuum pumps and have used refrigerator/freezer
compressors in a pinch. And change your vacuum pump oil often
if you use it to boil water as it “holds” the moisture.

John g
A Lighter Side
Portland, OR

    ...I don't believe that the suction gun and some of the
other devices described will pull an adequate vacuum for drying
parts. ....The whole point of using a vacuum is that water
boils, literally, under a sufficient vacuum. 

G’day: True, it does, but 'taint necessarily so for speeding-up
drying! When air pressure around a damp object is reduced, it is
easier for the molecules of water to fly around further and
faster so thus leaving the surface, as they are being bashed
and jostled continuously and are in constant movement even at
room temperature and pressure. So, the lower the pressure in the
immediate environment, the faster will the water molecules move
from the watch movement (for instance), and although the boiling
mentioned takes place quite violently at very low pressures and
normal room temperatures, it still takes place to a certain
extent whatever the pressure and temperature.

So, to sum up: to dry some object quickly without harming it,
gentle warming will assist; removing some of the air around it
will make the water evaporate more rapidly, and removing the
water by trapping it in some drying agent will accelerate the
drying process.

By the way; whilst silica gel is an excellent, harmless drying
agent, there are many others, such as anhydrous calcium chloride,
anhyd. calcium sulphate (gypsum or plaster of paris) quicklime
(calcium oxide) and even concentrated sulphuric acid! (used in
labs all the time) But I’m not really suggesting you should
pour it over your damp watch! Cheers and take off your watch
before showering, eh?

    / /
   / /
  / /__|\      @John_Burgess2

At sunny Nelson NZ


I guess we can all agree I’m no watch maker. I thought these
needed to be whiteroom clean and clinically dry. I actually
just open mine up and place it on a lightbulb to dry(-:

John g


Temperature and depth of vacum play key roles in using vacum in
dehydrating. At sufficent vacums ice will sublimate going
directly to a gas. However if the water is under oil it can’t be
removed by vacum without agitating, e.g. heating or mechanical
stirring etc. This is based on my observations of over 10 years.
The vacums needed are in the below 1500 microns range. (25,400
microns = 1" mercury vacum) with 0 microns being perfect vacum.
Changing the oil is important but I’ve found that running the
pump with the gas ballast open is necessary to clear moisture out
of the oil even when it has just been changed. I run the gas
ballast open slightly with the pump valved off for as long as
convienient to help dry out the pump oil. E-mail me off-line if
anyone is interested further @Dan_Wellman


Well I am a watchmaker and yes you have to be pretty clean but
I,ve seen lots of weird stuff with watches that actually
work…verdict is still out on Johns drying salts tricks and my
old Bulova cleaner dryer does work under partial vacuum with heat
and agitation together.

Terry Parresol


When I worked with a watchmaker years ago he used to take parts
and swish them around in isopropyl alcohol and they would dry
quickly. Careful not to put any delicate or dyed stones in the

Cary James,
Cary James Designs
P.O.Box 336 Manuels, Nfld
A1W 1M9