Rock™
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Reged: 03/18/12
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Mirror got scratch
#5645928 - 01/27/13 12:04 PM
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My 1st mirror was completed and sent for silvering to a local silvering glass people.
I am having another 6" glass so i thought to go for F/6 with it. Work was going fine, but at 1000 grit got a little deep scratch. May be abrasive is having ungraded particles in it. It does not got contaminated by me.
Can i ignore this scratch or should i degrade it with 600?
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kfrederick
Carpal Tunnel
Reged: 02/01/08
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Re: Mirror got scratch
[Re: Rock™]
#5646291 - 01/27/13 03:45 PM
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It is easy to get a scratch when using very fine grit Do not push the wet to long no down presure. Some do not like to go finer than 12 micron . I would fix it now if it is bad .A 6 inch f6 is a very nice size .
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Rock™
member
Reged: 03/18/12
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Re: Mirror got scratch
[Re: kfrederick]
#5647356 - 01/28/13 02:32 AM
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Thanks, just now i degraded to 600 grit and removed the scratch it and i also completed 800. Mirror is fine now.
As you know it is not possible to go for 1000 grit. Is it possible to move to Pitch And cerium oxide?
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GlennLeDrew
Postmaster
Reged: 06/18/08
Loc: Ottawa, Ontario, Canada
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Re: Mirror got scratch
[Re: Rock™]
#5647635 - 01/28/13 09:17 AM
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You could polish out after 800 grit (about 14 micron), but it will take a while. It's that last smattering of pits which will consume much time. Not so bad if you have a machine doing the work, but by hand, and if 'walking around the barrel', this could become drudgery. Mere minutes of work with a finer abrasive will save hours of polishing time.
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furrysocks
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Reged: 01/24/13
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Re: Mirror got scratch
[Re: GlennLeDrew]
#5647647 - 01/28/13 09:26 AM
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I'm not a grinder at all, but I read in the last few days that the fine abrasives can clump somewhat before they are mechanically broken down, and this can lead to scratches... solution may be to soak a slurry a day or two beforehand. Don't know if this helps.
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Rock™
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Reged: 03/18/12
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Re: Mirror got scratch
[Re: furrysocks]
#5647679 - 01/28/13 09:39 AM
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Thanks
@ Glenn i am not using machine , doing with the hand.
@ furry ok i will try to follow your advice to and lets see whether it works or not.
when i touch the 1000 grade carbo abrasive i do not feel like that i am having dust particle between my finger, but as soon as i put it in mirror ans start to grind, i can feel some dust particles done his job.
Will it save my time if i move to polish after 1000 grade?? 
Edited by Rock™ (01/28/13 09:40 AM)
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furrysocks
member
Reged: 01/24/13
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Re: Mirror got scratch
[Re: Rock™]
#5647689 - 01/28/13 09:44 AM
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Not meant to be "advice" as such - just relaying something I read. I can't even quote the source! 
You'll have to make your own choices. Grinding and polishing still seems like a dark art, to me! 
Good luck, though.
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ccaissie
sage
Reged: 09/13/10
Loc: Whitefield, Maine
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Re: Mirror got scratch
[Re: furrysocks]
#5648697 - 01/28/13 04:55 PM
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It is a good habit to gently put the mirror down on the tool, and before allowing gravity or pressure to take over, work the mirror around and distribute the grit for ~20 seconds. Any big grains will get broken up first. If you hear a crunch or two, lift it off and rinse it.
If your grit does have large particles, try mixing it up with water and a few drops of soap. The big grains will quickly settle, and then pour off the top into another jar and use that. I keep my grit in a little cup and brush it on.
I've had this problem with very good grit at 5 microns, and I think it had to do with rough stroking, or maybe clumping of the grit when it got too dry.
But you did the right thing...go back and fix it. Doesn't take too long, leads to happiness, and more practice.
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sopticals
sage
Reged: 03/28/10
Loc: New Zealand
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Re: Mirror got scratch
[Re: Rock™]
#5648813 - 01/28/13 05:43 PM
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Quote:
Thanks, just now i degraded to 600 grit and removed the scratch it and i also completed 800. Mirror is fine now.
As you know it is not possible to go for 1000 grit. Is it possible to move to Pitch And cerium oxide?
If you have a scratch  free surface after having completed the #800 grind, then its ok to go to the polishing stage. Your mirror will polish up quite  quickly using Cerium oxide.
Stephen.(44deg.S.)
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Rock™
member
Reged: 03/18/12
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Re: Mirror got scratch
[Re: sopticals]
#5649689 - 01/29/13 04:21 AM
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Thank you everyone, i tried using settle down larger grit and finally i succeeded in it. I did 1 hour of last 1000 grit and no scratch till now.
But i will not do any more with 1000 grit, i will move to pitch and cerium oxide.
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