18/02/2010

Week 4 (Week Beginning 15/02/10) Continued

Kiln Casting

At the start of week 3 I made a mould to make Sven a twin brother, but not an identical one. When I made the mould I made some space of excess glass by sitting the piece on some rolled out clay and cut around the edges to continue the shape and because the last one I did, I had to spend some time flat bedding the piece so it could be could on the glass band saw. This way I would have to do as much cold working and if I needed some glass cut off I could get it done faster. I used the same mould mix of Plaster, Silica, HT and water but I ended up having to get some more mould mixture after I had poured because I had made the walls around the mould slightly wider than I did the last time. When the mould had dried long enough so I could take away the walls I cleaned up the mould and removed the wax and clay using some tools. When I was happy the mould was clean enough I put the mould in the drying cuboard and left it there until Friday. I wanted to see if I could get more of the copper colour in the glass (without buying the Light Copper Oxide colour of the Gaffer Casting Crystal, which I am considering getting for my final piece of work) so instead of just sieving the copper oxide in I just tipped a load in (I know very technical) then brushed it around the mould to cover all the surfaces, I wanted to put some into the flowerpot reservoir I was using but I've done this before and it makes an orb of colour in the middle of the piece (not really what I wanted). Instead of doing a displacement test I took Sven and weighed him on some scales, he was about 680g. Then I weighed out 680g of glass but it didn't look like very much compared to the size of Sven, so I put and extra 100g in because I thought about hown I had needed to cold work the piece so I'd taken some weight off (not 100g but its better to have more than you need compared to not enough). When I had set every thing up, put the glass in to the flower pot and set up some pieces of kiln shelf to rest it on and put it in the kiln to cast over the weekend. But unfortunately someone must have opened it and forgot to turn it back on or I was a bit of a plum and forgot to turn it on - but I am very sure I turned it on. Anyway when I came in on Monday morning to see how the cast was going I discovered my glass set up just as I had left it (cold and un melted). So I locked the kiln and turned it on checking it repeatedly to check no one was trying to mess with my head....

Here is the kiln program I used:

100 ⁰C/hr → 550 ⁰C → Pass hrs
Full ⁰C/hr → 880 ⁰C → 11.00 hrs
(held longer to try to get rid of bubbles)
Full ⁰C/hr → 520 ⁰C → 15.00hrs
10 ⁰C/hr → 300 ⁰C → Pass
20 ⁰C/hr → 100 ⁰C → Pass
End

And here is how the piece looked when int came out the kiln:

After looking at this piece I'm starting to lean towards using coloured casting billets to get a consistent colouring throughout the piece, but I could still use copper oxide with the billets to add a bit more colour and detail to the pieces. Not sure yet though, especially as I have moved on to make my forms with a mixture of surface textures.


Gelflex Mould

In my last post I had started to develop a plaster modal with a mixture of curvy flowing surface to contrast the geometric form. I have decided that I want to see how this will look in glass so I flatted off the straight edges but hand laping the plaster against a sheet of sand blasted sheet glass and used sand paper to smooth out the curvy surface ready to make a gelflex mould of it.
When setting up my piece of plaster I sat my piece of plaster on a rolled out sheet of clay and cut around it to leave me with a bit of over flow when pouring wax after the gelflex is made and it will provide the overflow for my investment moulds. When I was waiting for the gelflex to melt I used a spray bottle to keep the plaster damp so the plaster doesn't stick to the gelflex.
The gelflex I used for this mould was my old one I had for making brothers for Sven, and after that had been melted it didn't look like i would have enough so I managed to find out an old gelflex that I had forgotten about to cut in to tiny chunks to put into the melting pot. I started heating the gelflex at 150⁰C but it was taking a long time for the gelflex to start melting even with the lid on so I turned it up to 165⁰C that seemed to work a lot better. It took around 2hrs to melt completely. When the gelfex had melted I turned off the pot and left it for just over 30mins and stirred it regularly. I think I may have poured it a little too soon there were a few bubbles rising to the surface, especially near where the point at the top of the plaster is. I usually leave gelflex to cool for around 45mins but in some of my moulds haven't picked up all the detail and there have been streaks in the gelflex, this is why I poured it earlier.
Didn't seem like too bad a mould but I'll have to wait until the mould has cooled completely so I can take the plaster out and have a look, and then I can go on to make a wax from it and see how my new form will look in glass. This wont be my final piece, it's just a test to see how the contrasting surfaces work together. I really want to see how the curves look when looking through the glass on the other side of the piece.
Also really proud because Mark our plaster technician (and a legend) commented on how beautiful the piece was *Happy Kimi*


Random Photo

Can't remember taking this photo, but I really like it...

"Hello Feet"



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