zOwie Omega Discussion Forum

: You need to get a response from Speedmaster Pro
: owners to get a balanced opinion of the
: Hesalite versus Sapphire crystal.

: From Jean-Michael's Web site see link below:
: Hesalite crystal of Speedmasters

: What is Hesalite : it is a brand name of a
: plexiglass , this is the material chosen by
: Omega to make the crystals of the Omega
: Speedmaster Professional. This was a logical
: choice in the end of the 50's but is it
: still a good material today ?

: The Speedmaster Professional is available today
: with either the Hesalite crystal or Sapphire
: , Omega keeps the Hesalite version because
: lots of customers still prefer a watch as
: close a possible to the one approved by
: NASA.

: I will try to expose here the advantages of the
: Hesalite crystal and explain how to polish
: off scratches on it.

: One of the biggest advantages of the Hesalite
: crystal is its shock resistance, I have
: personnally tested its resistance on a
: Speedmaster Professional crystal I had as a
: spare part : I have used a little watchmaker
: hammer to try to break the crystal : even if
: banged VERY strongly nothing happened to the
: crystal despite a real horrible noise ! I
: could not imagine performing such a test
: with the watch! the crystal then has been
: hit with a standard hammer ... and survived
: perfectly the test.

: Any glass or sapphire crystal would have broken
: in such conditions : the Hesalite crystal of
: the Speedmaster is really shockproof

Not to split hairs but... The correct material science term for resistance to shattering when hit with a hammer is "fracture toughness". Its possible watch people use slightly different terms from materials scientists or its possible that shockproof refers to things like how the movement will function after being dropped. This latter interpretation is what I had always assumed.