How to Remove AR Coating Tools

How-To: Remove AR Coating from Outer Crystal

Posted by Mike Johnson on in Tutorials

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Warning
Follow these instructions AT YOUR OWN RISK! With high speed tools there is always a chance you could damage your watch further if you’re not careful. If you have any doubt, take it to your local jeweler and have them perform the procedure professionally.

Anti-reflective (AR) coating is a feature prominent on many high end watch crystals, giving the watch face much better clarity from different viewing angles. Most watch manufacturers place AR-coating on the underside of the crystal, making it impervious to damage caused by external forces. Some manufactures also place this coating on the outside and inside of the crystal, typically referred to as double-AR coating. Treating both sides of the sapphire almost completely minimizes glare produced by external light sources, making the crystal appear almost non-existent.

While far superior for legibility purposes, the double-sided AR also has some critical drawbacks. Most notably, the AR-coating is not nearly as scratch resistant as the underlying sapphire, making it susceptible to hairline scratches and scuffs that would not normally impact an untreated watch crystal.

If you’re like me, you may be a bit OCD about the condition of your watches. Over time, an external AR-coating is going to accrue lots of small scratches, eventually negating the originally intended legibility benefits. When your watch reaches this point, you may be considering what your options are.

Luckily, with a little bit of effort and care, the damaged AR-coating can be completely removed from the watch, leaving a perfectly smooth and clean sapphire crystal underneath. In most cases, this doesn’t dramatically impact the glare resistance, as the underside of the crystal remains untouched.

What you’ll need:

Buying all of the tools on this list costs approximately $50.00.

  • Measure your bezel
  • Create your bezel mask
  • Apply mask to watch face
  • Carefully polish crystal

Making the Bezel Mask

When working on a watch crystal, it’s important to first mask off areas of the watch you don’t want to get damaged. In this case, the most important component to mask off is the watch bezel. While it is possible to do this without masking the bezel, you run the risk of polishing brushed surfaces or damaging the paint on an aluminum bezel. In order to make a mask fit perfectly, you’ll need to know the exact diameter of your watch face (excluding bezel). Using a Geometry compass, place the tool on the center of the watch and adjust the arm to reach the outer ridge of the watch crystal. Once calibrated, move the tool over to your masking tape and cut the appropriately sized hole. Take the piece of tape with the hole and place it exactly over the watch crystal, masking out the bezel and other surrounding elements. You’re now ready to polish.

Removing the AR-Coating

Removing the AR-Coating can be done by hand with a simple rag, but it takes a lot of time and elbow grease. With a Dremel tool, the AR-coating can be removed easily in 5 minutes or less. For the attachment, use a felt polishing wheel (one comes with the low-speed kit I’ve linked in the article). Apply a drop of Polywatch to the watch face and spread it evenly with a piece of cloth or microfiber. Using the Dremel tool, slowly polish the watch crystal with a low pressure in even circular motions, ensuring the you are constantly moving the polishing head and not staying on one spot for too long. It’s important that the tool is set to the LOWEST speed. It is possible to damage your crystal by applying too much heat or pressure. Take breaks every 30 seconds or so to make sure that the crystal is not getting too hot. Use a light source to determine where the AR coating remains on the crystal. After 5 minutes or so, the AR-coating should be completely removed.

Most Importantly:

  • Set your tool to LOW RPM
  • Move slowly and stop often to check progress
  • Don’t let your crystal get too hot

Use a cloth to remove any lingering Polywatch, remove the mask, and you’re done! Now you’re crystal is back to like-new condition. This same technique can also be used to polish out minor scratches in the actual crystal. Good luck!


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About the Author
Mike Johnson

Mike Johnson

Mike Johnson is the managing editor and primary contributor to 60clicks.com. Born into a military family as the son of US Navy pilot, Mike spent many of his formative years studying Computer Science and User Experience Design. When not obsessing over watches, Mike spends time hiking, traveling, and spending time with his family in Phoenix, Arizona.


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