Collector Guide Refinishing Hardlex Crystals

The lack of new, old stock crystals can be a real headache for collectors of vintage watches. Some watches use very specialized crystals either by virtue of the shape or the case fitment. When replacement crystals are not available, a serious choice must be made whether to fit a replacement of the incorrect type or live with the imperfections and signs of use. This is particularly relevant to collectors of vintage watches originally fitted with mineral glass which tends to scratch rather easily compared to sapphire glass. Seiko Hardlex, I am looking at you.

Have you ever wondered why so many vintage Seikos have incredibly scratched up crystals? The so-called ‘Hardlex’ fitted in most vintage Seikos has a Mohs hardness score of 5 like other forms of mineral glass. The Mohs scale, created in 1812 by German mineralogist Friedrich Mohs assigns a hardness score from 1 to 10 to various minerals. Diamond, the hardest mineral is graded 10 and Talc, so soft that it can be scratched with your finger nail is graded 1. By hardness we mean the material’s resistance to scratching rather than it being able to withstand a hammer blow… which would be termed toughness. A score of 5 is not very high. In fact household dust is harder than mineral glass with a score of 7 since it contains numerous quartz particles which are all harder than glass. So knowing that, it is really no surprise that Seiko’s Hardlex gets so scratched. Steel also scores a 7, which is why when you bang your vintage Seiko against the door knob, the door knob always wins.

Severely scratched Seiko high top crystal from an early 6119-6023 diver

For vintage collectors, this poor scratch resistance can be both a blessing and a curse. In some ways, that vintage watch with a crystal scratched to hell hiding an otherwise perfect watch is online auction gold. The 6119 diver pictured was one such find which had a perfect dial and inner rotating ring (still present) hiding under the damage. Many will judge such book by their metaphorical covers and not cross-check the auction photos from multiple angles to judge whether each and every imperfection is a superficial crystal scratch rather than some fatal dial damage. There is a sizable rush to be had when the dial is removed and the dial and hands underneath are found to be utterly flawless. However, that euphoria can be short-lived when all of your subsequent searches for a replacement crystal for your newly acquired beauty return precisely zero hits.

This is something I factor in to my collecting and the prices I am prepared to pay. Some time ago I acquired a manually wound 45KS King Seiko with perfect dial and hands below a moderately chipped crystal. Crystals for these King Seikos are rare and getting expensive and so I was not prepared to pay top dollar for the watch know I would also have to pay for a new crystal at current market price. The watch was still wearable of course but for my collection I do tend to like things as new or close to, so I bought the watch and planned to wait until a crystal became available. Three months later, I found a new, old stock crystal for sale in Japan that would bring the watch up to standard but it cost me almost half of the purchase price of the watch to acquire!

My 45-7000 King Seiko with the correct new, old stock crystal fitted

So what if replacement crystals are simply not available, rather than being just rare and expensive? This is when you need someone like Ben Levy who can perform the seemingly impossible and bring these crazed old crystals back to life. Since Ben has refinished a number of vintage Seiko crystals for me recently, I decided to find out more about his background and the process he uses to restore the crystals.

Refinished Watch Crystals
Refinished Hardlex crystals

Ben is an opal cutting and polishing expert from South Australia that has been working with these gems for over 35 years. For those who don’t know, and I certainly was not aware until researching more for this article, opals are typically found encased in sandstone with just a hint of their coloured potential showing through. It is the skill and experience of opal cutters like Ben that fulfill the opal’s potential, removing the sandstone carefully with rotating disks to reveal the glittering colours within. Cutting too far can easily destroy the iridescent layers of the gemstone, leaving only the decidedly less spectacular ‘potch’ opal beneath. It is not hard to see how these skills of analyzing what cutting is required, removing the smallest amounts of material and years of precise polishing experience could be put to good use in the watch world.

Polished opals
Cut and polished opals. Image credit: Ben Levy

Ben started refinishing crystals when a customer for one of his polished opals complained that the crystal on a watch he was restoring would never achieve the level of polish it had when new. Ben explains that opals are made from silica just like mineral glass and so he thought the processes of cutting and polishing opals could be adapted to refinish the mineral glass watch crystals.

Before and after Ben’s Hardlex polishing.

While Ben was naturally wary to go into too many details and give away some trade secrets, he did describe the overall process at a high level. First, he uses various grades of sandpaper on a dental lathe to do the fast cutting to remove just enough material to bring the level of the crystal down to the depth of the scratch. Not as much material as you probably think needs to be removed. Ben says that he does not remove more than 1/10th of a millimeter of material from the top of the crystal and the overall shape is retained. The next step is to move to a natural cerium oxide on a leather disc buff to smooth the crystal. The final stage is to polish the crystal at high speed using a diamond paste. Sapphire crystals can’t really be restored using this technique. Sapphire glass is extremely hard (9 on the Mohr scale) which means it can only be reground using diamond paste. Sapphire crystals are both brittle and very sensitive to heat such as that generated by Ben’s buffing equipment.

The hardlex crystals that Ben returned to me were perfectly polished and had the clarity of a brand new crystal. As a collector I prefer the idea of the original crystal being restored by a skilled artisan like Ben than a new aftermarket crystal being fitted. Such was the case with the 1972 ‘Resist’ blue-dialed 6139 you see photographed for this article. The watch is 100% completely original but was let down by a scratched crystal. Now after restoring the crystal, it looks fantastic again and it remains 100% original.

Perfect crystal refractions on the Seiko 6139

The only areas on the refinished crystals where defects remained were on one crystal that had two large chips in it. Ben does not use any filler when restoring the crystals so deep chips to the edge will be improved but sometimes not completely eliminated. Almost any other type of scratch can be fully removed and the refinishing cycle can be run two to three times to get the optimum finish. One of these chipped areas can be seen in the enlarged main image and I think you will agree it is tiny. Ben told me he thinks he can bring any crystal back to at least 95% of it’s original condition. From what I have seen, in reality the results are far higher than that.

You can reach out to Ben and follow more of his amazing before and after photos on Instagram where he is @levy_crystal_restorations.

Refinished hardlex crystals

Further Reading