Help - trying to do a 12" dia x 15" deep ring drop

[Gale aka artistefem]

............into a larger 15" dia rounded catch basin.

What to do - what to do?

What thickness glass will perform the best and how slow should I go?

Thanks

[Paul Bush]

The rule I was taught is you need two layers (3mm) for the first 2 inches of drop, then one additional layer for each additional 2 inches of drop. So for a 15 inch drop you would need nine layers of 3mm glass to ensure adequate wall thickness.

Have fun.

Paul

[jim simmons]

The rule I was taught is you need two layers (3mm) for the first 2 inches of drop, then one additional layer for each additional 2 inches of drop. So for a 15 inch drop you would need nine layers of 3mm glass to ensure adequate wall thickness.

Have fun.

Paul

That's right, Paul. Also, I would try a temperature of about 1250 to 1300 deg.F to start.

Jim

[Gale aka artistefem]

Thanks..........What I'm attempting is a one piece rounded top lamp shade with the lamp finial hole drilled in the rounded end part. I'll take off the lip and smooth the edges.

Any idea of how much the dropped glass walls will thin out? I've never made a drop this large. Do you think a nine layer thick glass shade will overpower the visual scale of of the lighting fixture itself and also be too top heavy, as in tipping over with the slightest breath of movement?

This table lamp fixture is a antique brass arts and crafts styled piece that has time worn pale yellow iris motifs painted on the upright. Sturdy, but visually on the lighter end of the crafts design movement.

The owner doesn't want the ususal stained glass shade that customary for these fixtures. She has asked for a kiln-formed shade that is simple and quiet in design. A design that leans more toward the oriental influences that were a part of some of the arts and crafts movement. Zen glass????

I intend to cold work the glass surfaces to a satin finish with maybe a hint of the iris design barely etched onto the inner bulb facing surface of the glass.

I'm open to suggestions about how to make a kiln-formed piece to meet these design specs................

[Jackie Beckman]

Instead of using a drop mold, which will force you to make such a thick shade, why not try one of the Ball surface molds from Bullseye. From what you save in using 5 or 6 less layers of glass, you'll easily pay for the mold, it will be less top heavy, you won't have to worry about cutting off the rim, it will be much easier to anneal and cool, and light will pass through it much easier.

J

[Brock]

I'm open to suggestions about how to make a kiln-formed piece to meet these design specs................

How about that French chick, Patty DeVere? Brock

[Gale aka artistefem]

Ball mold??? - I better take a look. Didn't even know there was such a thing. Is it an in-ny or an outie?

Yup Brock - I thought about trying that oui-la-wee method, but this is a pretty tall order. Gravity scares me - LOL!

Full mold with inner core or open face packed with alumina or whiting?

Thanks......

[Bert Weiss]

Gale

I think the approach I would try and hook up is a roll-up. A blower can get your deep shape without needing the thickness. Perhaps you could ship a few blanks to somebody with rollup savvy and have them blow them out for you.

[Gale aka artistefem]

Not a bad idea Bert. We have a newly arrived to our arts community, a glassblower and his partner who also does kiln-forming work.

They make some mighty fine glass work. Might be a good collaborative way for us to get to know each other.

Hmmmmmmmmmmm.......

[charlie]

did you take into account heat escape? i made a 1/2" thick potporri warmer, and a candle 4" under it caused it to crack. since the heat was concentrated in one spot, there wasn't even heat distribution across the piece, and ping.

[Gale aka artistefem]

Thanks Charlie.......

I'm looking at the possibility of using a vented metal heat cap. this could be done by enlarging the top end hole in the glass and then securely attaching the glass to perimeter of cap (sans foil and lead method). I need to look through the CR Laurence website to see if they have anything I might utilize for this project.

I'm also trying to visualize what it would look like if I intentionally abrasive blasted through the glass in a pleasing pattern in the top area. Could be tricky to do this though, without compromising the strength & integrity of the glass.

[charlie]

Thanks Charlie.......

I'm looking at the possibility of using a vented metal heat cap. this could be done by enlarging the top end hole in the glass and then securely attaching the glass to perimeter of cap (sans foil and lead method). I need to look through the CR Laurence website to see if they have anything I might utilize for this project.

weight. the glass will be too heavy for foil. you need something mechanical. stained glass lamps use spiders, with wire rims around the bottom sometimes tied into rods that go to the top.

I'm also trying to visualize what it would look like if I intentionally abrasive blasted through the glass in a pleasing pattern in the top area. Could be tricky to do this though, without compromising the strength & integrity of the glass.

that's more doable and a better idea. if you took out no more than 50% of the glass, it would probably hold together.

[Paul Bush]

Instead of using a drop mold, which will force you to make such a thick shade, why not try one of the Ball surface molds from Bullseye. From what you save in using 5 or 6 less layers of glass, you'll easily pay for the mold, it will be less top heavy, you won't have to worry about cutting off the rim, it will be much easier to anneal and cool, and light will pass through it much easier.

J

Aren't the ball molds only a couple of inches deep Jackie? If I understand the concept, she needs a pretty deep shade, hence the drop ring concept.

Theoretically, even though you are starting with a nine-layer blank, after the drop you should end up with about 6mm thick walls. The thickest part would be the rim, which is going to be wacked off anyway.

Paul

[Bert Weiss]

Instead of using a drop mold, which will force you to make such a thick shade, why not try one of the Ball surface molds from Bullseye. From what you save in using 5 or 6 less layers of glass, you'll easily pay for the mold, it will be less top heavy, you won't have to worry about cutting off the rim, it will be much easier to anneal and cool, and light will pass through it much easier.

J

Aren't the ball molds only a couple of inches deep Jackie? If I understand the concept, she needs a pretty deep shade, hence the drop ring concept.

Theoretically, even though you are starting with a nine-layer blank, after the drop you should end up with about 6mm thick walls. The thickest part would be the rim, which is going to be wacked off anyway.

Paul

Paul

I've cut a cross section of drop slumped glass. Most of the stretch is in the area below the part that is supported. Down in the center the glass is almost as thick as it started out.

[Jackie Beckman]

Aren't the ball molds only a couple of inches deep Jackie? If I understand the concept, she needs a pretty deep shade, hence the drop ring concept.

You're right Paul - I just looked again at the part of the post that said 15" deep. I'm not sure how deep the ball molds are available, but I'm guessing not 15"

[Lorelei]

Ok..maybe I'm the one who's thick here but I too want to make a drop ring vase with my new BE mold. It's about a 5 inch diameter middle and I was hoping to make it drop ohhh say about 6 inches or so. Following your instructions here, I'll set up the thicknesses of glass and fuse them, but how do I KEEP that thickness for when I want to slump? Glass will always want to be a certain thickness correct? (can't remember the exact number but I KNOW it isn't as thick as the piece will end up being without a dam of some sort) How do I dam it up on a normal kiln shelf?

[Brock]

Glass will only achieve it's equilibrium thickness. when it's HOT enough, LONG enough. You can fuse glass to a thickness greater than it's equilibrium thickness without dams. Brock

[Lorelei]

Ah HA!
Thanks! I had never heard that. It's most helpful to know.


p.s. Are you going to be at HGH in Portland in November?

[Brock]

. . . p.s. Are you going to be at HGH in Portland in November?

Nope. WGW in September.

Polarized Boy