Question: restoring a ceramic lap

Jared Eason

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I bought a used ceramic lap. Its very smooth , like glass. I have never seen a new one to know if this is right or not. I figured it would have some sort of texture to it. What can I do to restore it if indeed it needs it?
 

Brian Marshall

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S'posed to be smooth... it's not a "grit" disc.

Just a carrier for diamond powder...

Best way to clean it is with powdered kitchen sink cleanser (Ajax or the like), Scotchbrite & elbow grease.

Unless you have access to an ultrasonic and a steamer?


Brian
 
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Southern Custom

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As Brian said. The only abrasive power that the lap has is that of the Diamond spray, slurry or whatever is applied to it. Some use oil and diamond, some use water based sprays. It is for a fine polish only.
 

K Frei

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You can wash them, lightly with a SOFT brush and warm water and dry completely. I wouldn't be to worried about it being to smooth, i'd be more worried if it were textured. charge them lightly with 50,000 grit diamond spray. and your golden
 

Brian Marshall

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KFrei,


"Soft brush?" Why?


Hopefully, no one would use a wire brush, but even that would have no effect on the disc - other than to smear more metal into the pores... which is what cleaning is trying to remove.

A mild abrasive like Ajax is perfect for loosening the fine metal particles that get burnished into the ceramic surface.

If you do not clean it every so often, the pores get plugged up and the disc becomes ineffective...


Brian
 
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Sam

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I've scrubbed, scraped, acid-dunk them, and everything in between. I don't think there's a way to truly restore one to like-new condition unless you could remove the top surface and get down to fresh ceramic.
 

Brian Marshall

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Ah, there is a way... involving a hot acid bath in a spray booth system.

Used to be a lapidary guy who would make 'em like new for $20.


There are also flat lapping machines used for polishing large stone slabs, that surely ought to be able to give you a new surface?


Brian
 
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Sam

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Man, I'd pay $20 for that service any day. And yeah, a lapping machine would probably work. The surface of those ceramic laps gets glazed and slick and needs to be removed to expose the fresh ceramic below.
 

Jan Hendrik

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I can jump in here and give some advice. Take a piece of glass about 500mm by 500mm or slightly bigger (don't use glass that is too thin or it might break in the grinding process). Place the glass on a wooden top work table. Hammer in some nails next to the sides of the glass to prevent any sideways movement of the glass, but be careful not to break the glass with the hammer. Take 400 grit silicon carbide powder and sprinkle a pinch or two on to the glass surface. With a water spray bottle mist some water on to the glass as well. Place your ceramic lap face down on top of the grit. In a figure eight motion start grinding the surface of your lap. Try to keep an even pressure on the lap. Not too much pressure as the lap will tend to get stuck. If the grinding slurry gets too thick, spray a little more water and continue grinding. The silicon carbide grit will also wear in the grinding process into smaller particles. As you continue grinding the surface texture of the ceramic lap will get smoother compared to the first few minutes of grinding. If you find the grit is no longer grinding to your satisfaction you can add a little more as well as some more water. Stop after a while and turn the ceramic lap, then start grinding again in a figure eight motion. This is done to compensate for uneven pressure applied during grinding. The silicon carbide grit rolls around between the glass surface and the ceramic lap surface and in the process grinds away both the lap and the glass surface. You won't need to grind more than 20 minutes or so, except if there are deep worn grooves in the lap surface that you want to remove. If this is the case you will need to use a coarser silicon carbide grit to do the initial grinding.
I have been cutting cabochons since the age of 14 and have entered the Geelong international cabochon cutting competition at the age of 16 and achieve 11th place in the world rankings for that year. Gem cutting has been a hobby of mine for 23 years and I can do gem carving, faceting as well as cabochon cutting.
 

Sam

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Thank you Jan. That sounds like a good method and I would love to see someone do this!
 

Beladran

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I just run mine in the ultrasonic for awhile with the heat on. Comes out Snow White almost.. I really don't have to clean it much if all I'm using is glensteel but the second I put carbide on it it gets black fast
 

Ron Spokovich

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I've never tried the technique I'll describe, but with a bunch of stones that need cleaned, I just may depending upon if I can get some of the acid needed. For whatever stone or disk application, go outdoors with a china, dedicated large bowl, and one at a time, place the stone or disk within, level with a small level, and put water in the bowl 'til it just covers the stone/disk. Then, if you can get some 30% hydrochloric acid, carefully drip, slowly, the acid over the affected areas of metallic embedment. You should see a bubbling, like Alka Seltzer tablet advertisements. When the bubbling stops, the metallics should be gone. The acid is only meant to get rid of the metallics, and not the dirt or oils also trapped. . .should scrub first with Ajax or Comet, or the like. Please, wear a mask and goggles. DO NOT pour the acid in. . .use a dropper! I have heard that this technique is effective, but Jan's technique is safer.
 

Ron Spokovich

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Additional Safety Note

Forgetfulness setting in again, but also wear protective gloves, and thoroughly rinse the stone/disk when finished as hydrochloric can be bad stuff. A product called ZoomAlum(?), used for cleaning aluminum storm windows, and the like, caused a friend's hands to look as red as lobster's claws. Fortunately, he did heal up OK. Be careful!
 

Ron Spokovich

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Forgetfulness, again, and someone will no doubt pick up on the mistake. The hydrochloric acid treatment mentioned would apply ONLY to a stone, like a Black Hard Arkansas, and similar. I would also think the acid wouldn't affect a ceramic. I have some bigger new ceramic stones in hiding, somewhere, and as soon as located I'll run experiments. Aluminum disks, like the GRS items, should NOT come into contact with the acid, or disaster may prevail. Sorry for the error. Like anyone else, I make mistakes, and I'll be making more of them.
 

Jared Eason

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I wonder if I just lay it on top of my diamond laps working through the grits using the power hone, if this would grind off and more less surface grind it?
 
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