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Casting thick slab using Striking billets

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Casting thick slab using Striking billets

Postby lucy lyon » Thu Aug 26, 2010 9:19 am

I want to cast a 2" thick slab using 1823 billets. I have used gaffer gold ruby which strikes successfully, following their guidelines. Are There guidelines for using the bullseye striking billets? Have there been problems with carmelization using striking billets?
lucy lyon
 
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Re: Casting thick slab using Striking billets

Postby Jim Jones » Thu Aug 26, 2010 4:34 pm

Hi Lucy,

We have some information about our light pink glass (1823) under the Glass Tips section of our website.

http://www.bullseyeglass.com/education/glasstips/transparents.php#001823

Our light gold pink glasses, like 1823, need to be fired slowly during the initial stages of the firing cycle. If fired too fast they may not strike at all or they may strike, but appear spotty and have a blue-brown cast as opposed to the desired target color. The schedule located under the Glass Tips link above will work for two 1/8” layers of sheet glass. If you are firing thicker pieces we would recommend a more conservative initial heat of 200F degrees per hour to 1225F and then soak for two hours at this temperature.


Jim Jones
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
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Re: Casting thick slab using Striking billets

Postby lucy lyon » Fri Aug 27, 2010 12:10 pm

Thanks Jim. I'm going to be melting 1823 billets, about 8 of them to form a piece that will be about 7" x 19"
x 2" thick. I'm casting into a plaster/silica reinforced mold. It is open on the side that is 19" x 2". Generally I put as much glass as I can in the mold and the let the rest run in through a flowerpot. Normally I would have the temperature go up to 1600 over 36 hours. That's about 45 degrees F an hour. Do you think that will insure good color? If not, what adjustments would you recommend for the firing schedule? I think I have a good annealing schedule.
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Re: Casting thick slab using Striking billets

Postby Jim Jones » Fri Aug 27, 2010 3:05 pm

Hi Lucy,

We would use the firing schedule listed below. This schedule can be found in Tip Sheet #8 http://www.bullseyeglass.com/pdf/technotes_tipsheets/TipSheet_08.pdf

1. Initial heat, remove physical water

Rate: 100 F / Hour
Temp: 200 F
Hold: 6 hrs

2. Initial heat, remove chemical water, Quartz Inversion, pre-rapid heat soak

Rate: 100 F / Hour
Temp: 1250 F
Hold: 2 hrs

3. Rapid heat, process hold

Rate: 600 F / Hour
Temp: 1525 F
Hold: 3 hrs

I know you are experienced in casting, and the 45 F per hour up to processing temperature might work just fine, the only concern may be the slow ramp through the devitrification range (1350F-1450F). We would also suggest lowering the processing temperature from 1600 F to 1525 F and holding at the lower temperature for 3hrs or until you achieve the desired results.

I hope this helps.
Jim Jones
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
Jim Jones
 
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Re: Casting thick slab using Striking billets

Postby Twin Vision Glass » Sat Aug 28, 2010 7:19 am

Hello,
I was reading this thread with much interest. I truly love your work Lucy. Especially the arch pieces. (sorry , not sure of the name)
I tooo fire at a lower temp for longer. Jim, I was wondering if when you fire at 1525 ( I am having good success with 1480 and 1525 too) will the glass flow through the flower pot hole in only 3 hours. Perhaps if you really make the hole bigger. I tend to fire alittle longer at 1525 just in-case I have a bubble trapped but that is just me. I have even been having good success too at 1480 for 12 hours. Cast Bullseye I am finding also has those lovely little bubbles, and I am just embracing them as little jewels ,and find them to be the essence of the casting process. Almost like champagne.
I look forward to viewing the piece Lucy.
Les
Leslie Rowe-Israelson
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Twin Vision Glass
 
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Re: Casting thick slab using Striking billets

Postby Jim Jones » Sat Aug 28, 2010 7:52 am

Leslie,

Good point. We do enlarge the hole in the flower pot to 5/8" (16mm) to insure that the glass will flow into the mold.

Jim
Jim Jones
Bullseye Glass Co.
Portland, Oregon, USA
http://www.bullseyeglass.com
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