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casting cylinders

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casting cylinders

Postby michelle schouten » Sat Jan 15, 2011 6:25 pm

i'm attempting to cast hollow cylinders using 90 coe coloured, transparent glass packed inside cordite, hollow kiln posts.

i'm making the core of the cylinders of fibre rope wrapped in 1/8" fibre paper, wrapped in fibre paper for a more compressable core with a smooth internal finish.

I need to glue the fibre paper down like a home rolled cigarette so i can more easily pack glass around the core and into the cylinder. The glasstac doesn't hold.
Can anyone recomend a glue that won't adversely effect the firing process?
thanx
michelle
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Re: casting cylinders

Postby ejgiebel » Sat Jan 15, 2011 9:21 pm

OK, I've never done what you're attempting, but super glue burns off. You generally want to use it sparingly and put it in a place that it can vent off. I've read that Elmer's white glue (or similar) watered down 50% will work, although I've never used it. I have used super glue, it burns off well before the glass gets soft, and will dry quickly for you as you build the tube.
Ed Giebel
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Re: casting cylinders

Postby Stephen Richard » Sun Jan 16, 2011 8:04 am

A warm glass board suggestions was hair spray or spray glue. Just for those that do not follow both discussion lists.
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Re: casting cylinders

Postby sunnystrapp » Fri Feb 18, 2011 12:08 pm

Hi Michelle
http://hallmarkglass.com/index.php?opti ... &Itemid=49
is an interesting method somewhat akin to your endeavors. I suppose you may have developed a solution in the meantime but Mark Hall has some interesting thoughts if you are not working with a large team. You may pick up an idea for your line of work too. It has started my wheels spinning. Good luck sunny strapp
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Re: casting cylinders

Postby michelle schouten » Sun Feb 20, 2011 8:44 pm

ok colleagues
i'm ready to fire up the kiln to cast these cylinders and i'd like some feedback on my proposed schedule
the situation is:

there are 23 pieces in the kiln(evenheat 2451-13)
all filled with B90 clear and mainly transparent stringers, rods, cut up billet (max10mm thick),coarse and fine frit and a layer of 1/8" fibre between glass and inside cylinder
20 kiln stilt cylinders(10"x2") standing verticaly with a ROUND, central core of fibre rope wrapped in thin fire
3 rectangular prisms made of bisque fired clay lying horizontaly on the kiln shelf without cores, just glass
all on a kiln shelf

schedule proposed in degrees celcius:
55 620 1:00 heating up slowly to prevent thermal stressing 10mm billet strips
55 650 1:30 bubble squeeze
200 810 :30
9999 482 8:00
4 427 1:00
7 371 :30
20 30 off WHAT DO U THINK?
PS thanx to sunnystrap for the reply with photos informing me of mark hall's work on cylinders
i'll try to contact him and maybe we can share findings
michelle schouten
armidale
australia
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Re: casting cylinders

Postby Stephen Richard » Mon Feb 21, 2011 10:41 am

schedule proposed in degrees celcius:
55 620 1:00 heating up slowly to prevent thermal stressing 10mm billet strips
55 650 1:30 bubble squeeze
200 810 :30
9999 482 8:00
4 427 1:00
7 371 :30
20 30 off WHAT DO U THINK?

I think the soak at 620C is unnecessary. it is way above the the sub540C range where the heat up will break things.
I thing 810 is too low for a casting temperature. I would go to 850C for an hour or so.

From the schedule, I assume that you are firing the equivalent of 50mm of glass. Does this include consideration for the ceramic moulds?
It may be worth considering Graham Stone's schedules . For casting he does not really consider the glass, only the mould materials. So he suggests 80/hr to 160C soaking for 90mins, then 100/hr to 720 with another soak of 90mins, finally 130/hr to 850 for 6.5 hours
He suggests a controlled cool down of 330/hr from top temp to annealing soak.
This is what I think assisted by G.Stone - one of your compatriots, by the way. Get his book if you can.
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Re: casting cylinders

Postby morganica » Thu Feb 24, 2011 1:37 pm

I'd agree with Stephen, I'm not sure I see the point of holding at 620. I personally prefer doing a bubble squeeze by slowing down, not holding, at about that point. If I need a bubble squeeze I go down to about 10C dph between 645 and 670 or thereabouts, then add a hold at 670C to finish.

I might question how much air will actually be pushed out during a bubble squeeze if the pieces are stacked vertically inside the mold--the air needs to move past the glass and that's harder if several pieces above are softening and coming down at the same time, even with fiber paper.

I typically cast at about 812C, but my holds are much longer, usually at least 3-4 hours. That gives the glass time to become viscous and slip into mold crevices without the excessive flowing and scumming you can sometimes get from higher temps.

I would anneal for the entire thickness, i.e., from the outside edge to the outside edge, myself.

Only thing I'd really worry about is the thinfire.The glass will flow down strongly (which is what you want), but it tends to pull the softened refractory with it. It's not too bad with the fibre paper, but burned-out thinfire is 'way too delicate and can fold into the flowing glass and become trapped.
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