Thursday, June 2, 2011

Visit to a bronze foundry - sand casting

Following on from Tuesday's blog, I wanted to show you a little of the sand casting work we saw on our recent visit to the  Pangolin Foundry.

Large outdoor sculptures tend to be cast using sand for molds.  This involves huge three dimensional jigsaw puzzles of sand blocks formed around an original sculpture. The sand is mixed with sodium silicate. Tiny holes are made it the sand blocks and then carbon dioxide is put in the holes and the silicate reacts with the gas to create a glass type binding on the sand, making it a hard block.

The precision used in making the sand blocks was astounding with such straight surfaces and defined angles.

When all the blocks are made and hardened around the original, they are taken apart, the original removed and then reassembled. A core is then made, allowing a space of approx 10mm which represents the final thickness of the bronze.  The core is also made of the sand/silicate material, on a steel support frame.

The molten metal is then poured into the molds after the completed core and surrounding blocks have been encased in steel boxing.

Similar finishing work to that done on the lost wax cast sculptures is then done and patina is added.

Here are some of the other finished sculptures we saw:

Bronze covered in auto paint

Bronze Fish and Chips!

You can see this in a previous photo, upside down, before the bronze was poured in

It was an amazing tour and fascinating to see the processes involved in creating these enormous sculptures - some of them up to 100 feet tall!!

If you ever get a chance to tour one of the big foundry - go for it! You'll be fascinated too!

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