# polish mineral crystal with diamond paste



## tpd80 (Jun 28, 2011)

I attemped to polish out some scratches on a mineral crystal with some diamond paste and it hardly put a dent in it.

I'm using #7 grit (the smallest I have is 0.5).

Can anyone recommend an application/buffing method to get better results?

Thanks


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## James Roettger (Feb 1, 2009)

To remove heavy scratches you will need to "cut" the crystal down with a heavy grit first. Depending on the type of lap you use this heavy cutting could cause distortion or waviness in the glass. Usually several steps of compound are needed to go from cutting to polishing.


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## tpd80 (Jun 28, 2011)

Thanks, 

I have several grits i can work down from.

I was hoping for ideas on how to polish the glass. The crystal is flat and raised from the bezel a little so i just placed it face down on a hard surface with a sheet of paper between the hard surface and the mineral crystal to hold the polish in place and i made circle motions. 

I thought this would do the trick but like i said it hardly made a dent.


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## Tanguero (Dec 16, 2010)

I use a range of about 10 grades of diamond lapping pastes from 20 micron down to 0.5 micron and a thick brass block as a lap. Cleanliness between grades of paste is absolutely vital, as well as washing both the crystal and the brass lap, I file the surface of the brass with a fine cut file to remove any embedded diamond, before moving on to the next finer grade. I generally reckon with mineral glass that 5 minutes of lapping will remove all the marks from the previous grade paste, a sapphire crystal will take a *lot* longer. A tiny drop of fine oil on the paste helps keep things moving as well.

I try to work in a straight line and turn the crystal through 90 degrees with each change of paste - it makes it easier to see when you have completely removed the marks from the coarser paste. After the finest diamond I give a final polish with cerium oxide on a hard rayon felt pad. I have had good success with this technique on some really heavily scratched and chipped flat crystals.


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## tatraplan (Feb 6, 2012)

tpd80 said:


> I attemped to polish out some scratches on a mineral crystal with some diamond paste and it hardly put a dent in it.
> 
> I'm using #7 grit (the smallest I have is 0.5).
> 
> ...


Very easy to polish plastic based crystal with silver polish wadding such as Silvo, have not tried on minerals...


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## Henry Hatem (Sep 28, 2006)

Try Cerium oxide then the diamond to polish. If the scratch is deep your chasing your tail - replace the crystal.


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## dacattoo (Jan 9, 2011)

Crystals start at 2 dollars or less. Put a new crystal in it!


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## tpd80 (Jun 28, 2011)

Being in the "watchmaker" section I expected that to be one of the ideas. I haven't done much watchmaking but I might give it a try. I'm kind of shying away at the moment from all the crystal mounting methods I have read about.

I'm worried to get in to deep and not be able to fix it without equipment that costs much more than 2$.



dacattoo said:


> Crystals start at 2 dollars or less. Put a new crystal in it!


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## Guest (Mar 23, 2012)

A watchmaker would put a new crystal for cheap, so you do not need tools


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## WristFiend (Feb 21, 2012)

tatraplan said:


> Very easy to polish plastic based crystal with silver polish wadding such as Silvo, have not tried on minerals...


Brasso, you guessed it... a brass polish, works even better! Cheap and relatively weak - will req. multiple passes.


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## RustyMainspring (Nov 16, 2010)

I'm a watchmaker and we put in new crystals. Trying to polish out a scratch is a big waste of time. Just replace it dude


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## BananaaMan (Nov 14, 2013)

Just finished polishing out a 2mm scratch from the crystal using diamond paste - took about 1.5hrs!!! (Maybe best to get a watchmaker to replace).

If you want to polish it yourself start at a 5micron or more and work down it steps to 0.5 or 0.25micron if you have. Remember it will get worse before it gets better.


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## dacattoo (Jan 9, 2011)

brasso?????


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## Somewhere else (Feb 17, 2006)

Henry Hatem said:


> Try Cerium oxide then the diamond to polish. If the scratch is deep your chasing your tail - replace the crystal.


This is what watch makers do. I7m surprised nobody mentioned polishing with rouge. It removes light scratches and is a good final polish after Cerium oxide and diamond.


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## lysanderxiii (Oct 4, 2006)

Is this a special/odd size or shape Mineral crystals cost about $3 to $5 each, more cost effective to just replace it. (And throw in a new gasket.)


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## tpd80 (Jun 28, 2011)

I'm the OP.

I couldn't seem to reduce the scratches so I ended up getting a local watch maker to drop in a sapphire crystal for $20.

Since then I have learned a few things and ill probably be putting the crystal in my self next time.


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## Precise (Mar 27, 2011)

This worked very well for me on an old Waltham pocket watch with a slightly domed glass crystal and _deep_ scratches.

After first trying fine grits, I got serious and switched to 320 grit carborundum paper on a small wood block. I sanded wet. The paper only cut when fresh and it was a waste of time not to change to fresh patch of paper every 20 seconds. It took an hour to get all the deep scratches out. I sanded the entire crystal. The scratches from sanding were much finer than I expected.

Next I sanded wet for just a few minutes with 1,000 grit carborundum on the wood block. At this point is was quite nice.

Next I rubbed it with felt and a dab of Wenol polish. Wenol is the same pink color as cerium oxide, which I've used to polish telescope mirrors. So it probably_ is_ cerium oxide.

The end result exceeded my expectations. The crystal looks like new.

I think it was important to back the grit paper with a flat block. I think if I'd just used my fingers I would have dished the locations of the deep scratches.

Alan


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## Precise (Mar 27, 2011)

Today I tried the above process on a Fortis Flieger crystal which had a lot of medium-fine scratches. They were not as deep as the Waltham that I polished in the prior post. Instead of holding the grit papers on a small block, I laid a large sheet grit-up on a flat surface and worked the crystal (still in the watch) against the wet sheet. This spread the work over a much larger amount of grit paper and seemed faster than changing grit on the small block so frequently.

The grinding phase went ok, but Wenol polish did not produce a gloss. I finally resorted to yellow diamond paste applied with a pine block, and got a gloss. I suspect that this crystal might be sapphire, which is standard for the original manufacture Fortis. But if sapphire, I'm surprised that it had so many scratches. Furthermore, I would not expect sapphire to respond to my grit-paper grinding as well as it did.

Alan


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