Many unbreakable plastic watch crystals are made of tough acrylic plastic that can be susceptible to scratches. Don’t just throw out your old crystal when you start to see scratches on it, use this guide to polish those marks away with the help of a sanding stick and a polishing stick.
Be aware that you can only polish away scratches. If your crystal has very deep scratches, we recommend that you use a motorized method to remove them as it will take a lot of effort to do it by hand. And, if your crystal is chipped or cracked you cannot fix it by polishing and you will have to replace it completely. Check out this link to learn How to Replace a Watch Crystal.
- A sanding stick
- A polishing stick
- Crystal polishing compound bar
- Polyimide tape or masking tape
- Soft crystal cleaning cloth
The first thing you should do is prepare your watch for polishing. To protect the finish on the watch case while you buff the watch crystal, you will want to take your polyimide tape and use small pieces about an inch and a half long to cover the metal around the crystal. Overlap the pieces of tape to completely cover the metal around the watch crystal and give your watch the illusion of having a mane.
Once you have covered all the metal, examine the scratches in the crystal again, more closely:
If they are deeper scratches, you will want to follow this guide all the way through, starting buffing with the sanding stick. You will want to be sure to use a fine grit 4/0 sanding stick, to avoid doing unnecessary damage to the watch crystal.
If the scratches on your crystal are fairly light ones that don’t appear to require much work to remove, you can skip ahead to Step 6 and start right off with polishing your crystal.
You’ll start by buffing away the deep scratches on the crystal. Hold your watch case with its protective tape securely in your non-dominant hand. Be sure to keep your fingers from the edge of the crystal so you have room to work the sanding stick. Then, take the sanding stick in your other hand and carefully begin to buff away the scratches. Use medium-light pressure against the surface of the crystal and move in nice even strokes covering the whole surface of the crystal to avoid over buffing one area. Be sure to keep the crystal and sanding stick on an even plane toward each other to maintain the flat surface.
If you are working with a curved or domed crystal, be sure to always keep the buff moving against the crystal along the curve so you can maintain the nice curved edge. You will use a little more angled buffing in this situation.
Stop frequently and take the sanding stick away from the crystal to check your progress and make sure that you are not over polishing any particular section.
After you get a feel for how your buff is working with your plastic crystal, you can increase the pressure between the sanding stick and the crystal to work more quickly but be careful not to over sand and accidentally create grooves in your crystal.
Repeat Steps 3 and 4 until you can no longer see those deep scratches you noticed when you started. Be aware that it might take longer than you expect to polish a plastic crystal by hand.
Once those scratches are gone you can trade your sanding stick for the polishing stick to smooth away any rough patches you created and light remaining scratches.
Next, set your watch case aside so you can apply your crystal polishing compound to your polishing stick. Hold the polishing stick firmly in one hand and rub the polishing compound against the felt end of the stick with even strokes using medium pressure. Roughly five strokes should be sufficient to lightly coat the felt polishing stick in the compound.
When the polishing stick is coated with the crystal polishing compound you can set the compound aside and take up the watch case again.
Use your polishing stick to remove any remaining faint scratches with even strokes across the crystal face being sure to get around the edges of the face as well to remove any remaining signs of scratching from the surface.
Once everything looks smooth and even, set your polishing stick aside and remove the polyimide tape from the watch case.
Then, use your soft cleaning cloth to remove any remaining excess polishing compound from the face of the crystal and any remaining adhesive from the watch case.
When that is complete, your crystal should look just like new and you can start wearing it again. For other handy methods for polishing watch crystals, check out our Learning Center for more articles