How to polish an acrylic watch crystal

If you have a scratched round acrylic crystal, no problem – buy an new one and replace it. It’s a bit harder if your crystal has an odd shape and is hard to come by. In that case, it’s elbow grease you will need!

This Tissot SeaStar crystal is pretty badly scratched. Let’s see what we can do.

Before you polish, you have to get rid of the deep scratches. So the first step is a 240 grain abrasive paper. Make sure you have enough thickness left on the crystal to get rid of even the deep scratches, it not, you will have to leave some of them.

As the crystal is standing proud of the case and there is no chance of damaging the case, I can leave the crystal in. Otherwise, you have to take the crystal out of the case.

In this case, we have enough thickness, and I take off the acrylic until all the scratches are gone.

Looks a bit like snow …

Next step is a 500 grain paper.

Always make sure you have a smooth surface before moving up to the next grain. After the 500, it’s 1200.

After the 1200 paper, you can see where this is going. Now we’re moving on to a 2000 grain.

Still milky, but getting better. The last paper we will be using is a 9 micron 3M lapping film.

After the 3M 9 micron lapping film. It’s still a bit milky, but a great surface for the buffing wheel. So I charge the buffing wheel with some Dialux vert, and take the crystal to it.

This is the last step. Don’t apply too much pressure, and rotate the crystal as you polish.

Not too shabby, and I’m happy with the result. Now you have to clean the case thoroughly to get rid of all the debris. You don’t want acrylic dust to end up in your movement!

9 thoughts on “How to polish an acrylic watch crystal

  1. I’m currently working on a TV Tissot square crystal of about 1970 ….. (It had a very deep ding and a lot of scratches), following this how to has resulted in a super clear crystal.
    Not having all of Christian and Mitka’s equipment, after the 2000 grit paper, I used a 3000 waterproof paper and a bit of water for a “wet lap”.
    Finally, a gentle rub with micro cloth and Brasso, clean up and a wipe with a lens cloth, ………I’m really proud of the result !
    Thanks for a super “How To”

  2. Good tutorial.

    For small scratches I hand buff using regular bathroom toothpaste. It works wonders on very small scratches on my datejust’s plexi!

  3. Good piece, Christian. For those who need to finish crystals by hand – I needed to as I had to reface a Zodiac SST glass, replacements no longer available and tricky as they have track transfer stuck underneath, which means no power tools (too hot!) and VERY careful with water (or else!) – I can highly recommend a product called Micro Mesh, available through eBay in handy 6″ x 4″ pack assortments for around £7.00.
    It starts at grid number 1000 and goes down to 12000, similar to lapping film in effect, but a bit more durable and longer lasting.
    I’ve learned that the best method is to do regular overlapping sanding, each 10 strokes at right angles to the previous. Circular scratches are harder to work out, I find.
    As Christian suggests, start with a cutting paper – I use wet/dry 600 – to get going, and then, as above, progress all the way down to 12000. A final polish with Polywatch or similar and you will have a super shiny and scratch free finish.
    I find that I can solve the most difficult of problems – I’ve worked out gouges and pock marks – using this method, a process born from necessity, but useful for other needs when power tools are too agressive or threaten adjoining surfaces.

  4. I love the “How to” posts. With enough of them, I may become brave enough to try one! Your good work is much appreciated, Christian. Thanks.

  5. Great blog. Thank you…

    Just noticed that you’re using Draper-grinder/polisher. Would you recommended it for polishing stainless steel?

  6. In addition to not wanting to get acrylic dust in your movements you really don’t want to get it in your nose, throat or lungs… dust masks are to be recommended 😉

    I use a polishing compound called Polywatch for minor surface scratches, but anything deeper and I just tend to order new acrylic – hadn’t ever considered going down the route of completely re-surfacing but can certainly see the benefit of being able to do so with hard to replace acrylic.

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