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How to Successfully Polish Seiko Hardlex Crystals?

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SeikoWatchLover

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Discussion starter · #1 ·
Dear Experts,

I have a number of Seiko watches with scratched Hardlex crystals.

Has anyone managed to successfully polish out the scratches on Hardlex?
If so, please tell the secret.

From what I've read,
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Hardlex Vs Sapphire: The Hard Truth About Dial Windows - Wristweargear

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on the MOH hardness scale,
"Seiko’s hardlex has a rating of 8"

Which is pretty hard, considering that diamonds have a hardness of 10.

...

Here is what I've tried so far,

I bought some diamond paste.
Grits from 400 to 8000.
And polished by hand with microfiber cloths.

Interestingly, the polishing cloths don't change color at the coarser grits.
But do change color with the finer grits, from say, 2000 and finer.

So, it seems that the coarse grits aren't working, but the finer ones are
Go figure.


After the polishing, the scratches are not as noticeable.
They don't reflect the light as well.
But they are still there if you look for them.

...

So, I bought some loose silicon carbide, 220 and 400 grit.
And tried polishing with that.

It didn't seem to make any difference.

...

Do anyone know, what is the secret to getting the scratches out of Hardlex?

Thanks
 
Discussion starter · #2 ·
Firstly, thanks to all of you, for your responses and suggestions.
:)


Here is an update on polishing Seiko Hardlex

I've been working on this since December 2021
Now it is August 2022.

Some background. I've fixed up many cars in the past.
Including touching up, and polishing the body.

So, I'm familiar with polishing.

But I've never had anything so challenging as Hardlex.

This was the diamond paste from Tech Diamond Tools

Interestingly, the coarser grits didn't seem to work at all.
But the finer grits did.

See the polishing cloths. Only with the finer grits, did the cloth change color.

Image
 
Discussion starter · #3 ·
Lots of hours searching, and many hours of emails to multiple sources.

Ebay, jewelry suppliers, rock polishing suppliers, etc.

I mentioned that Hardlex has a hardness of 8 on the MOH scale.
What do they have that they thinks might work?

As for the responses, I was appalled.
NO ONE knew the basics of their own products!

They would recommend products that were softer than Hardlex.

Even when grit was their only product,
no one knew how hard their grits were!

If grit is your only product, I do expect that you know more about it than I do.

...


One guy on Ebay, had listed diamond powder as
Grit 40 microns.

So I emailed, is that 40 microns, or 40 (sandpaper) grit?
He responded, 40 microns

Then I asked, what is that in sandpaper grit?

He responded that it was only sold in microns!

Huh? It's a standard conversion. Like
Miles to kilometers. Celcius to F.
Gallons to liters

But he didn't know! Unbelievable!

At Tech Diamond Tools, they actually list both measures on the same line:

...

One guy sold silicon carbide, which has a hardness of 9, and other products too.

So I asked which of his products would work on Hardlex.
Let him make his recommendations.

But he failed to answer the question.
Just asked me questions. Huh?

...
 
Discussion starter · #5 ·
I also ordered some diamond sandpaper on Ebay.
60 to 400 grit.

But I only used the 400 grit.

It worked well too.

When I say it worked well, the diamond sandpaper
actually took material off the crystal.

And, it also left lots of scratches that had to be
sanded out with finer and finer sandpaper.

Image
 
Discussion starter · #6 ·
I even tried using my dad's old orbital sander.
Dry sanding.

Don't remember the grit.

But dry sanding just didn't seem to do much.

It did change the color of the sandpaper a bit,
meaning, at least some material was coming off of the
Hardlex crystal.

But nothing dramatic. The scratches were still there.

(Why can't I rotate the image on this website?
As soon as I inserted it, the image rotated 90 degrees )

Image
 
Discussion starter · #9 ·
Some more:

Later, I got more black sandpapers from the automotive store.
Unfortunately, they did not list the material.

The range of grits was:
2500
2000
1500
1000
800
600
320

They worked closer to what I had hoped/expected.


Image
 
Discussion starter · #10 ·
Wet sanding

With these sandpapers, I only did wet sanding.

I should also mention; before starting, the
watch was disassembled. most components were
removed from the watch; movement, crown, back.

The only things left with the watch were the
case, crystal and strap, so I could hang on to it.

One thing with wet sanding though.
When the crystal is wet, I couldn't see the scratches anymore.
:(

So, I had to dry the crystal with a tea towel to check the progress
and see if the scratch was out.


.......
 
Discussion starter · #11 ·
Boo boos:

One thing I did was to wet the watch, and the sandpaper, and
Layed the sandpaper on the deck.

Then moved the crystal back and forth over the wet sandpaper.

Flat, and lots of leverage; this was working good.

Then suddenly, the sandpaper buckled, and I got
another scratch on the crystal!

So, eventually, I just did it all manually.
No blocks of wood.
Just used my thumb to move the sandpaper over the crystal.

Doing this, the sandpaper didn't buckle, and
give me another scratch.

Image
 
Discussion starter · #12 ·
...

Another boo boo was that early in these experiments, I
had opened up the strap, and both ends of the strap were loose.

I took the watch to show some others what I was doing.

Later, I noticed that there was now a scratch on the INSIDE of the crystal!

So, the strap had flopped inside the crystal, and scratched it.

This took a lot longer to get out than the scratches on the outside.

So, after that, I kept the spring bar in the strap, to keep it closed.
And, I was careful to always have something in between the strap and the inside of the crystal.

I suppose that I could put the case back on, but I like to look through the crystal.

Odd, the Hardlex is harder than stainless steel,
but the stainless steel made a blemish on the Hardlex.

Go figure.

Image
 
Discussion starter · #13 ·
...


After the sandpaper, I then used some other polishes I've
heard about, and also used on cars.

Fine cut cleaner
Colgate toothpaste
Headlight polish
Scratch X
Aluminum mag/aluminum polish
Brasso


I'm not sure that these really do much on Hardlex.
As the polishing cloths don't really change color.

While I was at it, I also tried the same products on the stainlesss steel strap.
Then, the polishing cloths turned black.

Image
 
#17 · (Edited)
So what's the bottom line? Diamond paste from 400 to 8000? How much does that cost to buy? Looks like 8 tubes - what are the grits ?

I wonder if dry grit in a rock tumbler would work - or it might round off the edge & screw up the fit / water seal.

You could try dry grit in a container, stick the lens on a dop stick and rotate it with a drill, pushing the convex face of the lens into the grit. It would raise dust, so punch a hole in a lid just big enough for the stick.

I like your vintage Craftsman sander. I have a Sears circular saw with a stainless steel case.

What's the best stuff to get the haze off plastic car headlight lenses?
 
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