Flame Fusion is a 100 year old process for making gems, Sapphire Crystals, and the Rubies in watch movements. Invicta has decided to use this term to mean something a bit different.
So what is Flame Fusion (other than Invicta's definition)? I read a bunch of articles but I'm certainly no expert. There is considerable information available about using Flame Fusion to make synthetic gem stones, but very little about watch crystals. But the processes for each are related. Anyway, here is a bit of what I found out:
Rubies and Sapphires are both varieties of Corundum. Both can be produced synthetically using Verneuil Process, also known as Flame Fusion
, invented by French chemist Auguste Victor Louis Verneuil, in 1902. Higher quality gem stones are produced by other methods today but the more affordable Flame Fusion method is still used for watch movement rubies and sapphire crystals.
How Flame Fusion Works:
A column of Ruby or Sapphire (a "boule") can be manufactured in a Verneuil furnace. Powder size aluminum oxide particles are sprinkled down though a oxyhydrogen flame to melt at over 2000 degree Celsius. They fall onto a column where they crystalize just below the flame. This leads to the name Flame Fusion - particles fuse to each other as they fall below melting point and crystalize. The column of crystalizing material is slowly lowered away from the flame as it grows in height with more crystalizing particles fusing to the top of the column.
Here is an easy to understand movie that shows the process for Rubies
are made in much the same way, building a long cylinder that is sliced and polished.
The process is described in many articles online but this is a good one:
History is here:
Some Interesting Points I Found in My Research:
"Nowadays, the production capacity of sapphire for watch windows and other applications is 250 tons (1.25 × 109 carats), the largest fraction from the (Swiss) Djevahirdjian factory with 2200 Verneuil furnaces, and this with the practically unchanged process."
The Development of Crystal Growth Technology
HANS J. SCHEEL
SCHEEL CONSULTING, CH-8808 Pfaeffikon SZ, Switzerland
"Watch "glasses" manufactured on the base of leucosapphire and light-colored sapphires are used by all well-known manufacturers of high-quality watches. This is not a fashion. You will see no scratches on such "glasses.""
Sapphire: Materials, Manufacturing, Applications
By Elena R. Dobrovinskaya, Leonid A. Lytvynov, Valerian Pishchik
The primary use for Verneuil-grown sapphire and ruby today is still for synthetic sapphire and ruby gemstones, watch jewels, watch windows, and the process is virtually unchanged from the original design.
There are other synthetic crystal producing processes that have been developed as alternatives to Flame Fusion. All probably owe some of their background principles to the original Flame Fusion method. Some produce higher quality precision crystals for use in optics and semiconductors.
Watches don't need higher precision in more modern methods. Flame Fusion remains one of the most cost effective ways to produce rubies for watch movements and sapphire for crystals.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and you'll have his shoes.