Friday, September 16, 2011

Out Cast!

Tafe - Weeks 24 -28

I haven't blogged lately so here's a rundown on the last month or so of Tafe lessons.
Our project was to design and carve a piece in wax, ready to cast.

First up - research & inspiration :) After many hours of web browsing and looking through books, inspiration was eluding me! Who'd have thought that it would be while flicking through a Store catalogue junk mail that I spotted a dinner set and inspiration finally hit. The contrast of the plain square shaped plates with their lovely fluid curved profile appealed to me. Then on the next page I spotted a set of bathroom scales and loved the dots! Finally I had a starting point.....

The next step was to sketch out some designs, so the drawing lessons we did earlier in term had come in handy already. I'd come up with a couple of designs but in the end I abandoned the triangular idea (Swiss Cheese anyone!) in favour of the curved square with some dots and texture.

Next step was the tech drawings which had to be to scale. Drawing comes naturally to many people - unfortunately I'm not one of them..

Then on to the wax carving. I started with a block of Green wax and the fun began. Sawing and shaping first  then carving out the shape. My shape was much easier to form than the knot I carved out in an earlier lesson, so this step went pleasantly quickly.  Once the front surface was shaped and sanded smooth I applied the surface texture - I used a bur to make the little concave depressions and a scribe to make the scratched lines.
The thing with casting is to get the wax as light weight as possible, so the back had to be carved out so it wouldn't use more metal than necessary when casting. Also, the piece can't be too heavy to wear - the weight of a piece in sterling silver would be about 10.5 times the weight of the wax. So I set to work with a bur in a pin vise to hollow out my wax.

 The wax block is a dark bottle green - the aim is to have it looking a consistant pale translucent green when it's held up to the light.

Later I did lots more tidying, carving and sanding and the final wax weight was about 3 grams. I was really happy with the finish and so was the teacher! The better the finished wax model is- the less work needs to be done on the cast metal piece. I didn't take a final pic though as we sprung into action in the afternoon getting our pieces sprued up and into the flasks to pour in the investment, which is like a super, super fine plaster of paris.

For those not familiar with casting: the metal flask contains the wax model with the hardened  investment around it, and  is placed in a kiln to heat up - the wax melts out leaving a void in the investment. About 6 to 8 hours later the flask is removed from the kiln and the molten metal is poured into the hot investment and fills the void so the shape can be replicated in the metal! There's a bit more involved but you get the idea.

Which brings us to this week's lesson - The flasks were in the kiln and we busied ourselves drawing colour renderings of our designs..... these had to be a standard suitable as if to present to a client. Now mine doesn't look too colourful really but that's what happens when you are drawing silver!  I used 4 shades of grey and an indigo!

Still with me? A bit long winded I know, but this is the condensed version of about 5 class days!  I suspect that you will be dissatisfied with the ending of this story though!

After being removed from the kiln, a little piece of investment chipped away from inside the flask. Not sure what happened as I was busy melting my silver at the time, but it chipped in a crucial location and any silver poured in at the top would have gone straight through to come right out the bottom!
There was lots of speculation about what caused the investment to chip off - possibly my positioning of the wax in the flask (not enough clearance - don't think it was this) or my prep of the investment (hmmm - quite possibly) or it could have been no fault of mine - the flask could have been knocked going in or out of the kiln or any number of other mystery reasons.  
The lecturer tried a last ditch attempt to cast anyway by plugging up the chipped investment with wet paper towells but by the time we got the silver remelted the flask had cooled down too much and the silver just spat back up out of the flask during the pour. My casting had failed!
My piece went from  "one of a kind" to "none of a kind" in the space of a few minutes (insert sad face here)
Here's the remnants of my silver which I reclaimed from the investment and the work bench. 

Teachers and fellow students were mortified for me but on the upside, (there's always a silver lining eh? oops - excuse the pun - sorry!) I won't have to spend next week's lesson removing my sprues and cleaning up my casting!

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