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Casting a 35cm x 30cm x 20cm piece with clear bullseye glass

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Casting a 35cm x 30cm x 20cm piece with clear bullseye glass

Postby lowyyeli » Tue May 14, 2019 4:21 am

Hi all,

I recently wandered into the world of glass through my university architecture project, which is based around glass. To represent some thoughts I have on incorporating glass into architectural features I decided I wanted to cast a glass object representing a corner piece where the floor meets the wall.

I made a hollow mould with a plaster quartz mix and filled this in with bullseye glass I smashed into small pieces myself. When the programme ended and I opened the kiln, the reservoir on top where I put more frit glass had casted so I presumed that the rest of the inside was casted too. It is important to note that I made sure there was a 5cm thickness around the volume that I wanted to cast just to make sure the mould did not crack open due to the 10kg weight of glass added inside.

Unfortunately, I have just started to remove the mould and noticed that only the first top 4cm of the mould has casted, the rest remain exactly as the frit I put into the mould. It never reached a temperature high enough to even deform. (Please refer to the picture) To be honest, I've never casted glass before and also never used this kiln to cast glass before so I was going in blind. Due to tight deadlines in architecture school I just had to go for it.

Failed glass cast
IMG_4095small2.jpg (190.95 KiB) Viewed 6279 times

This is the schedule I used:

Segment 1; Target 50c. Ramp 50c p/h. Soak 4 hours.
Segment 2; Target 675c. Ramp 220c p/h. Soak 30 minutes.
Segment 3; Target 825c. Ramp 330c p/h. Soak 15 minutes.
Segment 4; Target 480c. Ramp 999c p/h. Soak 8 hours.
Segment 5; Target 85c. Ramp 300c p/h. Soak 4 hours.

Did I use the wrong programme? Was the plaster cast too thick that the heat never made it through the plaster to the glass?

I would really appreciate any thoughts and tips.

Thank you!
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Joined: Tue May 14, 2019 4:04 am

Re: Casting a 35cm x 30cm x 20cm piece with clear bullseye g

Postby marykaynitchie » Thu May 23, 2019 11:52 am


Kiln-glass can't be rushed, and all of us have learned that through our own similar experiences. ;)

That looks like an ambitious project for your first time kiln-casting in glass! Have you read our articles on kilncasting?

Was your mold made similarly to the technique shown in this article? http://www.bullseyeglass.com/methods-id ... sting.html

What were the various thicknesses of the walls and floor of your piece? This article will give you advice on the annealing (controlled cooling) ramps.http://www.bullseyeglass.com/methods-id ... slabs.html

If you are interested in architectural glass, please have a look at Bullseye Studio's website. it has lots of examples of architectural kilncast glass that we have fabricated for artists and designers, for public art, and private buildings. https://studio.bullseyeglass.com/

I don't do kilncasting myself, so I will need to get some help if you need further advice. Let me know if the article helps.

Mary Kay
Mary Kay Nitchie
Bullseye Glass Co.

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