Using Shell as an inlay - questions

[Jim Underwood]

Bonnie Campbells recent question on shell inlays reminded me of something...

On one of my last trips to the beach I spent a lot of my time picking up shells that I thought might make an attractive inlay for box tops.

Unfortunately, my first couple of attempts chipped out pretty badly even using sanders and sandpaper. Once I had the piece almost shaped, I only had a small 1/2 cabochon shape with a few chips out of the edge.

So I have this whole bag full of pretty shell pieces just waiting to be worked.

Any ideas how one might go about processing this material?

[Nathan Hawkes]

Jim, I have NO experience with inlaying shell pieces, but I have years with saltwater coral & invertebrates via high-end aquariums (I used to install & maintain them). I don't know if you're crushing them or trying to get the outsides of the shells as an inlay, but a lot of shells that look beautiful on the outside are pretty boring once their outer layer is chipped or sanded off. A lot of the patterns that appear on snail & other shells go but only so deep, then the pattern is very very faint, and ends up as a very light beige or pink tone with the cross section of the shell. Calcium carbonate is pretty hard stuff--probably relatively similar to turning marble, but most shells are very thin. I don't remember the term for it for sure--I think its called nacre in oyster shells, but the outside of most shells when they're still fresh & shiny is somewhat like the enamel on our teeth----thin but a lot harder than the inside. Its pretty brittle stuff. I don't know how to go about turning it successfully, except maybe in some sort of clear acrylic resin, much like the trinkets you see in desert tourist shops with scorpions inside paperweights.

[Jim Underwood]

Nathan,
I'm not wanting to cut away the top layer of the shell; as you say, that's the prettiest part.

I'm just wanting to make the "bottom" fairly flat, and grind/sand/turn the perimeter round.

I've mostly chosen pieces that will lend themselves to a very slightly domed cabochon shape.

I just need to know how to shape them so they won't chip so badly.

[Nathan Hawkes]

Gotcha; I wasn't sure if the cabochon was intended or an improvisation from the chipout. In that case, I would think that setting it in epoxy would be the only option, and letting it cure for several days to fully harden first. You could also try some dremel bits meant for masonry removal. Just keep the speed up & the cuts very light. Its not exactly turning, but if you're careful, it would work. I guess I didn't really explain the shell right; part of the shell's brittleness is due to its structure. You probably already know this, forgive me; but the entire thing is a sandwich of layer upon layer--hard/soft/hard/soft. It lays on new layers to make the old ones thicker--kind of like tree rings. I think you're going to have to cut it with an abrasive wheel first, then shape it by hand, or epoxy it into a block that you can shape the bottom of.

[Ron Ainge]

Jim

I am making ornaments out of sea uschin shells and when i fit the fininals in the top of the shells I do use a Dremel to round out the hole. I have found that if I use the grinding wheels at high speed I get the best results. As you know the shells are very brittle and they break easily. I have not tried to grind a shell round but I think that you could do if you can stabilize the shell while you grind away the unwanted parts. I would suppose you could turn a crowned support out of wood and then use some clay to support the shell while you work on it. Best of luck on the project and let us see what the finished product is.

[Doug Shepard]

Jim
I dont know much about turning but I might be able to help with the shell flattening as I've been flattening some small pieces of abalone lately for inlaying. I definitely dont have the right tools that somebody who does this a lot would probably want but after some trial and error found a method that works reasonably well.
1) Cut a slightly oversized blank out of the shell with a jewelers or fret saw. I think the blades I have were somewhere around 20+ TPI. This works best if the good shell side is the convex side of the shell otherwise the flattening is going to remove the visible layer and the layer you end up with isn't as interesing as the starting one.
2) Put some doublestick carpet tape on some wood or ply scrap and push/twist the good side of the shell down onto the tape. So now you've got the concave side up. You cant do much at all with power tools until you can hold it flat and I couldnt find any good way to clamp or hold the stuff. The carpet tape wont do this but it will let you hold it OK enough to use hand tools.
3) Start with a course file and start filing until the dish is gone. I was using a Kutzall (sp?) I got at LV, This takes about 5 minutes. Then remove from the tape, flip it over on a finer file for another minute or so. At this point it's probabaly not 100% flat but getting close.
4) On a flat surface lay a piece of sandpaper down and work the piece back/forth until done. 60g works faster but has more friction and grabs a bit so 100g is what I ended up settling on. If the piece is small wadding up a small scrap of carpet tape on the end of your finger will help get a grip for sanding and keep from sanding your fingertips
5) Use Liquid Hide Glue and glue down on scrap wood with blue tape clamps and let it se for 24 hours.
6) Remove the tape and you can start drilling/dremeling/whatever. If you got a good glue bond it will stay put and you'll hav backing so that it doesn't chip.
7) When you're done drop it it into hot water and the shell will fall off the wood backing in a few minutes. I was just using water out of an Insta-Hot. I was making plugs so drilled the shell/wood with a plug cutter and popped the plugs out. You might have to cut around the shell with a saw if you aren't making something round.

Not the most elegant solution but it worked.