Timepieces:Education & Repair
Water Resistance Tests: Why and How
Once you understand how the tests are conducted, you can offer a valuable
service by explaining them to customers
By David Christianson
Certified Master Watchmaker
President, American Watchmakers-Clockmakers Institute
Pressure is a bad thing in life but a good thing in a watch because it
keeps water out of the case and away from the movement. In this second part
of an article on water resistance (see also "The Need for Water Resistance
Repair," p. 64, July 1999), we examine how rubber gaskets and the case
work together to protect the delicate watch movement from dirt and moisture.
If your store can conduct the test efficiently, customers will likely consult
you again for future purchases and repairs.
One basic rule: the thinner the gasket, the less protection it will provide.
For instance, the 0.4mm case back gasket provides minimal protection against
accidental exposure to rain and moisture. A watch with this gasket most
likely couldn't resist the pressure and would leak if placed in only one
meter of water (about 3 feet) in a pool, lake, tub or spa. At this depth,
the watch case is subjected to an additional 1.3 pounds of pressure (measured
in pounds per square inch). Under 10 feet of water, the case would face
an additional 4.3 pounds per square inch and would leak even faster.
As with the gasket, the thicker the case, the better the protection.
While thin versions of both can be used for minimal resistance, the thicker
cases and gaskets found on diver watches and others provide stronger resistance
A watchmaker or watch repair person should look at gaskets routinely when
checking water resistance. This is done typically after servicing a watch
movement to assure it remains dry and dust free within the limits stated
on the watch.
These tests are done in a workshop with a pressure tester (either wet
or dry) or a vacuum test (used primarily by large-volume test centers or
The wet pressure tester is most common among independent jewelers. The
watchmaker places the cased watch without its strap on the shelf in the
upper dry half of the tester and sets the pressure control to the limits
indicated for the watch.
Once the pressure is built up in the tester, the repair person lowers
the watch into the water-filled bottom half. At this point, the air pressure
in a leaky case would be equal to the pressure of the water in the tester
water couldn't enter and air couldn't escape. But when the air pressure
valve on the tester is released, the air in the leaky case would have greater
pressure than the water around it.
In the case of a leak, bubbles form, showing the faulty section of the
gasket or the problem section of the case. If the watch is removed immediately
while the air is still escaping, it isn't damaged.
If no bubbles appear, the case and gasket are holding out water at the
indicated pressure. The seals are deemed tight and the gaskets are secure.
David Christianson is fourth-generation owner of Christianson Jewelry,
Kendallville, IN. In addition to serving as AWI president, he is a certified
master watchmaker and a fellow of the British Horological Society. He discusses
watch repair for the sales staff in this column each month. Send questions,
suggestions and comments toProfessional Jeweler, 1500 Walnut
St., Suite 1200, Philadelphia, PA 19102; firstname.lastname@example.org.
Copyright © 1999 by Bond Communications.