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Playing with Fire.. and Sand

melting scrap silver in a crucible

Delft clay casting (a.k.a. sand casting) has been on my to-do list for ages and I finally did it! :) Sand casting is an ancient technique where the moist sand is used to form a single-use mold for pouring metal. I had a bag of Delft clay sitting on my studio shelve for about a year but I still needed a few other things and just kept procrastinating.

Thinking back, my major obstacle was the clumsy mold frame I got with the clay. I did not like it at all. Typically, Delft clay is sold with a set of small aluminum rings but I decided to get a more versatile (or so I thought at the time) traditional sand casting flask. It is bigger and can be used two ways. 

sand casting molds traditional flask vs handmade square mold---  The beauty and the beast. Traditional cast iron flask vs an elegant handmade solution by Peter at ---

After trying to fill the large flask with sand it became obvious that it's way too large and it takes forever to fill properly. It's also very heavy (cast iron!) and the positioning pins do not provide a tight fit to ensure precise match of the two sides. 

I went searching for an alternatives and while shopping around for the standard rings I found a rather good looking square versions. I first spotted them on Ebay, but their maker also has a standalone website. I got the 7cm square and I love it. The sides fit together perfectly with zero play and it's a pleasure to work with. 

delft clay casting mold with seashell impression--- This carefully constructed Delft clay mold of a seashell will be destroyed after it's filled with hot metal. ---

For my first sand casting model I've chosen a thick seashell fragment I've picked on one of my trips - I'm pretty sure it's from Greece. It has a gorgeous deep texture with lots of fine detail, freeform rounded edges, and enough thickness to make a good casting mold. 

scrap silver for melting---  Scrap silver ready for melting --- 

All this time I've been carefully sorting my leftover metal into two separate jars - one for clean silver scrap, and another for bench lemel and silver pieces contaminated with with solder. I finally have a chance to start emptying the clean scrap jar :) 

melting silver for pouring--- Melting about 20 grams of sterling silver. The 4th try. ---

I'm using an Orca torch (a.k.a. EZ torch) with propane for melting silver. It's ok. It feels a bit slow (it probably is), but eventually silver scrap turns into a shiny rolling blob ready to go into the mold. 

delft clay casting---'s all inside... did I get it right this time? This is one nervous moment. ---

 finished sand casting of a seashell --- YAY! It's not the full shape, but it's still very good. --- 

 sand casting sea shell--- 1st through 4th attempt at pouring silver into the mold. The 2nd one was a complete flop LOL --- 

 side view of sand castings ---  Side view of the castings. Third time's a charm :) ---

Forming the mold in the clay turned out to be relatively easy job. It's fiddly and requires lots of care, but it's very doable. Pouring the hot metal into the mold is another matter - I need lots more practice with it...

close up detail sand casting --- Close up detail of the 3rd seashell casting. Love it!--- 

 sand cast silver seashell fragment --- Cleaned and pre-polished silver shells.  --- 

I will continue trying to pour the full size shell model just for the heck of it, but I really love the organic looking fragments of the fragment. It makes them really unique and it perfectly suits the nature of my object.

cleaned sprue of the casting--- Cleaned and lightly textured backs of the silver shells. Ready for the next step.. whatever it may be :) --- 

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