How is this achieved?

Having the outer shell completely removed, leaving only the pearl shell...

Probably muriatic acid.

Probably muriatic acid.

+1. Can't remember wwho does it but I've seen ones where justhe crustaceans are taken off leaving the red on the outer shell.

I imagine using more acid or soaking in acid longer, it would turn out like the pic.

acid will not corrode the pearly part?

rough sanding to fine sanding to polishing????

acid will not corrode the pearly part?

I've never done it myself but I think it would eat away at the pearl if you let it. Just gotta watch and rinse it when you think it's done.

The sanding sounds like it would work too but using a small amount of acid to get out the sand marks instead of polishing. There's probably many methods to doing it. Never having tried any myself I wouldn't advise using what I've said to do it.

Someone with some expierence will probably chime in on this.

Those look exactly like the paua shells they sell in NZ. I believe there's a grinding or sanding process involved which I've heard is very dangerous. The particles are very sharp and can get into your lungs and do serious damage, supposedly. Not worth messing around with unless you have some quality safety equipment.

Muriatic acid will eat any part of the shell it touches, I've used it and it's quite effective, if you try it start by diluting it like 10 to 1 otherwise it works too fast.  Also Muriatic (hydrochloric) acid at full strength is very corrosive and harmful to skin and eyes, be careful with it.  I've heard but not tried it myself that you protect the parts you don't want eaten away by covering it with vaseline. 

I tried the sanding and polishing thing and that stuff is really hard, I've also heard that the dust created is toxic and harmful to the lungs.  Not sure about that.

Bleach or CLR works well to. That and a wire brush and some elbow grease. Just farting around with some old shells in the yard and they came out ok.

Ive seen shells like that at the Randall museum in SF Maybe some one in their arts and crafts department could help you out with more info on the sanding part. The acid will get you down to the red part but a sanding chisel not sure what its really called could chip the rest of the red off leaving behind the pearl coating. Im going to start murric aciding my shells to the red some time this summer I believe Abking aka loletaeric has a vid of the shell cleaning.

Wes

I talked to a guy who sold them while I was Ensenada a while back. He said he used a wire wheel. Use a good respirator.

The Paua shells are usually cleaned of deposits with dilute hydrocloric acid then sanded smooth and polished. Not a very peasant job that should be done with wet wheels and a dust/mist collection system. I wear a respirator and use a wet grinder to shape and polish shell for inlay jobs.

The dust created through the grinding and cutting of abalone shell is dangerous; appropriate safeguards must be taken to protect people from inhaling these particles. An N95-rated dust respirator, a ventilation system, and wet grinding are requirements to working abalone shell safely. The calcium carbonate dust is a respiratory irritant and the particles can penetrate into the lower respiratory tree and cause irritant bronchitis and other respiratory irritation responses. The usual symptoms are cough and sputum production, and secondary infections can occur. If there are proteins left in the shell matrix, it is also possible that they can trigger an allergic (asthmatic) attack. Allergic skin reactions can also occur.

I've met people who had wrecked their lungs doing shell inlay and jewelry without proper safeguards (emphysema,lung cancer).

I have done this with sonoma coast ab shells. You need to find a shell that is relatively free of worm holes so its going to be a smaller shell more than likely. I first took a 24 grit grinding disk and started removing the red layer. Then I sanded with 80 grit on an orbital sander until the grinding marks were gone. Then sand with 150 grit and then 240 grit. Wet sand the finished shell with 800 grit. Then use clear coat in a spray can. they are making some good spray can stuff these days. DO NOT BREATH THE DUST AT ALL! This is paramount. You will get sick from it. You can get a respirator that will protect you by buying one at an automotive paint store. These are used in the painting process and will filter out all dust if worn properly.

A friend who owns a body shop did it using the method Craig describes

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I wonder if you get the same effect with media blasting of some sort...