Delft clay casting with silver

Hi, does anyone know if the Delft clay casting technique would be suitable for copying small sea shells in silver. I’d like to copy small mussel shells, just 1 half.

I’ve watched a few YouTube videos and done some searches on this forum, I suspect that the thinness of the shell might be an issue.

I’d really appreciate any advice for a beginner.

Thanks
Steve

The short answer is yes, just fine if the back is flat or convex. If the back needs filling in you can use molten wax, for instance dripped from a candle, BluTack, Fimo, or anything else you have. Dennis.

Hi Dennis Many thanks for the advice.
I was hoping to keep the back of the shell concave, but maybe add fimo or similar to the concave side to thicken the shell a little.

If I then press the half shell into the sand, convex side down, up to the rim of the shell, I guessing that may work?

The correct way to fill the flask is to build up the sand around the pattern not press the pattern into the sand especially with a sea shell it would most likely break, sand is quite tough, also pushing the pattern into the sand will create deformation around the pattern. If you have not done any sand casting before, I suggest you try something a bit more robust the get the feel of the process.

Bob is correct but there may be a way to work around the problem of the shell strength. Thicken the shell with a meterial that will harden so that you have the cross sectional thickness you require, you mention clay but you could use something like milliput, car body filler or epoxy glue with some stiffening agent in it. Once it has hardened and it has been cleaned up, pack some of the Delft clay into the concave side and place this on a flat surface. Overfill it slightly and press it down onto the flat surface so that it is stable. Place the mould plate over the top and pack the casting sand over the top. When this is done turn up the other way and use a cocktail stick to loosen the sand in the shell and remove with a soft brush. Use the cocktail stick to ensure that your joint will be in the correct place and clean any residue away with the soft brush. Add the other mould plate, use the talc as a separator and pack the other side of the mould with the Delft clay. Split the mould and cut your sprues in the usual way. Be prepared to do this more than once ;-). I've not tried this but it should work provided the sand stays in the concave side of the shell. You may have to may have to place a flat surface over the upturned shell and turn both up the right way together so that the sand does not fall out.

I hope this helps.

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Originally Posted by china

The correct way to fill the flask is to build up the sand around the pattern not press the pattern into the sand especially with a sea shell it would most likely break, sand is quite tough, also pushing the pattern into the sand will create deformation around the pattern. If you have not done any sand casting before, I suggest you try something a bit more robust the get the feel of the process.

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You make a good point there. Thanks.

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Originally Posted by alastairduncan

Bob is correct but there may be a way to work around the problem of the shell strength. Thicken the shell with a meterial that will harden so that you have the cross sectional thickness you require, you mention clay but you could use something like milliput, car body filler or epoxy glue with some stiffening agent in it. Once it has hardened and it has been cleaned up, pack some of the Delft clay into the concave side and place this on a flat surface. Overfill it slightly and press it down onto the flat surface so that it is stable. Place the mould plate over the top and pack the casting sand over the top. When this is done turn up the other way and use a cocktail stick to loosen the sand in the shell and remove with a soft brush. Use the cocktail stick to ensure that your joint will be in the correct place and clean any residue away with the soft brush. Add the other mould plate, use the talc as a separator and pack the other side of the mould with the Delft clay. Split the mould and cut your sprues in the usual way. Be prepared to do this more than once ;-). I've not tried this but it should work provided the sand stays in the concave side of the shell. You may have to may have to place a flat surface over the upturned shell and turn both up the right way together so that the sand does not fall out.

I hope this helps.

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Many Thanks for the detailed advice, It sounds like it could work, although it may take a few attempts. I may well try something simpler as my first go at casting and then return to this, I suspect most people use the lost wax process for thin shells, but that’s not something I currently want to invest in.

Hi, had my first go at Delft casting. I used a small beach pebble.
It went well despite me making the fill channel a bit narrow.
See attached photos.
Thanks for your help
Steve

Attachment 12522

Attachment 12523

Well, nothing can stop you now. Well done. Dennis.

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Originally Posted by Dennis

Well, nothing can stop you now. Well done. Dennis.

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Thanks Dennis, early days for me.