Best way to polish old mineral crystal?

[bodymassagewatch]

I've got a couple Seiko 6139's with pretty rough crystals. I was able to get about 75% of the scratches out, but it's not the sparkling result I've often see posted by others. I've been starting with a 1000 grit sandpaper(too chicken to start any lower than that), and then I jump straight to 2000 grit, using some #2 and #6 polishes in between, which has yielded what i'd call average results. I know they're only around 40 bucks to replace, but i'd love the satisfaction of being able to do it myself! Does anyone have a tried and true method to restore these old crystals?

[jdm]

If the issue is the deep scratches, you can't get them off with 1000, start with 280. Abrading glass is not like working  to paint or metal.
Then at the end you can't get good finishing with paper only,  crystal will always appear  kind of blear. Use diamond paste on a felt wheel, mounted on a rotary tool. Don't bother with paste below 20 grit. Both paste and the tool, in case you haven't it, are very cheap on AliX or similar sites.

[bodymassagewatch]

7 minutes ago, jdm said:

If the issue is the deep scratches, you can't get them off with 1000, start with 280. Abrading glass is not like working  to paint or metal.
Then at the end you can't get good finishing with paper only,  crystal will always appear  kind of blear. Use diamond paste on a felt wheel, mounted on a rotary tool. Don't bother with paste below 20 grit. Both paste and the tool, in case you haven't it, are very cheap on AliX or similar sites.

I've got a dremel with the small felt wheels, that should suffice? I will need to pick up some of that diamond paste. Like I said, I've been trying to use the two polished below, finishing with Peak Cream. I think starting at 1000 grit was my biggest problem. Will pick up some rougher grit SP and give it a whirl. Worst case scenario is a ruined crystal i know i can replace!  

[jdm]

The above are mild abrasives, they do nothing to glass. 

There are various polish thread on this forum, use the search function. Anyway:
Place the wet paper on a plastic support disc 5 - 8 cm diameter.
Observe from inner side that  you are hitting to the correct spot, orthogonal to the scratch direction. You will see white streaks on the point you're abrading.
Check often and as soon the scratch is gone then move to 600, that's the finest grip that will have some effect. After that you'll need diamond paste.
You can't ruin a crystal unless you drop and chip it. Of course, on a faceted crystal, crisp edges cannot be preserved.
 

Edited May 25, 2019 by jdm

[bodymassagewatch]

2 hours ago, jdm said:

The above are mild abrasives, they do nothing to glass. 

There are various polish thread on this forum, use the search function. Anyway:
Place the wet paper on a plastic support disc 5 - 8 cm diameter.
Observe from inner side that  you are hitting to the correct spot, orthogonal to the scratch direction. You will see white streaks on the point you're abrading.
Check often and as soon the scratch is gone then move to 600, that's the finest grip that will have some effect. After that you'll need diamond paste.
You can't ruin a crystal unless you drop and chip it. Of course, on a faceted crystal, crisp edges cannot be preserved.
 

Thank you, not only for the information, but the level of specificity and detail! I do appreciate it

[canthus]

Done a couple of seiko hardlex glass crystals basically using process of wet/dry then diamond pastes.  It is essential that the crystal is thoroughly cleaned after each polishing step before moving to a finer grit. This is to ensure that any of the previous grit is removed as it will only scratch again when the finer grit is applied.  No short-cuts and patience is essential as it can take a long time to get a really good clear finish.

[bodymassagewatch]

1 hour ago, canthus said:

Done a couple of seiko hardlex glass crystals basically using process of wet/dry then diamond pastes.  It is essential that the crystal is thoroughly cleaned after each polishing step before moving to a finer grit. This is to ensure that any of the previous grit is removed as it will only scratch again when the finer grit is applied.  No short-cuts and patience is essential as it can take a long time to get a really good clear finish.

Thanks for confirming the process canthus. I've no problems taking time to do it, I'm just glad I'm now sure what the process is. I've got diamond paste on order!

[vinn3]

if it is a flat crystal,   I use a " lapping plate"  with all the above paper and compound.  I have had good results with glass and modern crystals.    vin 

[Doninvt]

If a scratch is deep, you might be better filling it with something with  a similar index of refraction rather than taking down the whole surface.  Maybe that stuff they use for filling chips in windshields.

[jdm]

8 hours ago, Doninvt said:

If a scratch is deep, you might be better filling it with something with  a similar index of refraction rather than taking down the whole surface.  Maybe that stuff they use for filling chips in windshields.

Not sure what are you talking about, but that's just not doable. Deep scratches can only be repaired by careful sanding, followed by polishing.

[mikepilk]

I polished some very deep scratches out of a crystal using a #1000 diamond coated whetstone (use water). It was a hard crystal as wet and dry paper did nothing. 

I then polished with diamond paste using a small felt disc on a Dremel