Goblet construction Question

[zip]

Greetings,
I have a question about goblet construction.

I make my cups, stems and bases separately and anneal them.
Now when you attach the parts together would you stick it in a preheated kiln or would you let them cool then place in a cold kiln and bring up to annealing temp. ?

The latter is what I have been doing and on closer inspection a few of my goblets show cracks adjacent to some connection points.

Your expertise and experiences as always greatly appreciated.

[TlkQ]

It seems like it'd make sense for any weld to go into a hot kiln and then get ramped down.

[zip]

Tlko I know what you mean. My thinking was that only the welds were hot but the most of the goblet is cold to warm at best.

[hashmasta-kut]

there is no point to annealing the components before assembling. you can assemble them cold off the bench, and then place the goblets in the kiln, and anneal it once.

[purdy]

I do it all cold and just flame annealing along the way as needed. then when it is done, I'll ramp it up and anneal the sucker completely. Its fun, it makes you get your flame annealing down straight. good luck.

[Aussie]

I'm a great fan of avoglios. You can prep a foot and a cup with an avoglio on each and let them bench cool while you're working on a stem (depending on whether it's a drawn stem or a more complicated worked stem, of course). Once you're done with your stem and while it's still hot it's quite easy to assemble everything quickly and putting the avoglios into the flame is not a problem, as the shape of the avoglio dissipates the heat quite nicely ... those clever Italians, eh?

[Bo Diddles]

Hey Aussie can you explain the proper (or "classic") construction of an avoglio?

[Aussie]

oh, gee, it would be easier to show it. Basically I do it two ways.

1. I pull a point, constrict one side, blow up the bowl or foot blank. Then take the point on the constricted side off and melt it so it's a little nub. Then I add a gobbet of glass and shape it into a fat cylindrical shape and constrict it while holding my jacks or pachioffis at an angle, occasionally shaping the end of it down a little to cool it down somewhat and have something to push against.

2. Pull out a point and make a test tube bottom on one end. Apply a gobbet of glass to that and proceed as before.

I modified my pachioffis by cutting off the wooden pegs and inserting graphite rods about half an inch in diameter. These work a bit better than the jacks, because the rods are round, they set up the constricted shapes of an avoglio with ease. You can also use diamond shears to set up the shape in a pinch, but I find those a little bit unwieldy. Alternatively you can also use the edge of your L marver or a V necking tool or just roll down on a single round graphite rod. Or you can just attach a punty to the end and pull it out a bit and then push a maria (although this won't give you the same strong shape as jacks or pachioffis will give you).

Basically, while I prefer my graphite pachioffis, any way you can get the shape quickly is valid. It's that rounded, constricted shape you're after. Aesthethically, you'll be shooting for a strong, crisp shape.

[Bo Diddles]

Thanks a lot Aussie, I hadn't ever given much thought to avoglios before I saw Sizelove's goblet video. Always more going on in glassblowing than what I take in at first glance, especially with traditional Italian techniques.

[Bo Diddles]

Damn I can't rep you.... yet.

[Aussie]

I hope that makes sense :/
Avoglios are one of the first things I learned in the hoshop, they're very handy. Lucio Bubacco also uses bowls and feet which he prepares beforehand and the avoglios are handy because it allows him to heat at a point which is away from the glass. Very important for soda glass.

[Robert Mickelsen]

Bubacco once told me that he did not anneal his very large, complex sculptures because "annealing caused more problems than it solved". Instead, he annealed each individual component and then assembled them all using avoglios. I wondered how this was possible and he explained that the avoglios somehow dispersed the stress in a way that the piece did not crack later. It seems the hourglass shape has something to do with it.

My theory is that the glass cools more rapidly in the "waist" of the avoglio and so bends the lines of stress into a "U" shape that is a little more parallel to the surface that they would be if the connection were a cylinder. The "U" shaped stress is less likely to fracture than perpendicular stress would be. By carefully managing the heat so that only one side of the avogio is heated during assembly, Bubacco could get away with constructing massive and complex structures entirely cold out of soft glass!

http://www.whokilledbambi.co.uk/public/2010/11/fisherdevils.jpg

All of that said, I don't use avoglios much. They just don't fit my style somehow. I actually prefer the exact opposite - a kind of shallow bi-cone - for my connections. Go figure.

- RAM

[daveabr]

I had the pleasure of watching Lucio work up close, for an entire weekend once. The assembly he does with soft glass is nothing short of mesmerizing. The speed with which he does it, makes it seem as easy as snapping legos together.

[J Howard]

yeah, he's absolutely amazing to watch- incredible technique, timing, and dexterity


as for your goblet question, annealing is not a silver bullet for glassblowing - a better heat base is. if you can, spin your feet out on the stems. this will make them much stronger because your the heat base will flow up in to the stem and disperse evenly across the foot. the foot and stem will be much closer to "one" piece of glass. if you just take a cold foot and weld it onto a cold stem, you get hot glass next to cold glass. annealing will take some of the stress out, but often not enough. set that cup down on a granite counter top too hard and it will easily break. this is probably where your cracks are coming from. feet spun out on stems will put up with far more abuse, and will be noticeably stronger. they also bench cool just fine if cooled off vertically. best part about this method, is that you can punty to the underside of the foot right after it's made. it's extremely difficult to do that to a premade foot without cracking it. being able to punty to the underside of a foot makes attaching a cup to the top of the stem amazingly more simple. better yet, if you can drop a bubble onto the stem and actually open it while puntied to the underside of the foot, the whole cup will be perfectly centered to itself, stronger, and more attractive to the eye as well.

sometimes spinning a foot out is impractical for a particular shaped stem. you can attach a cold bench cooled foot to the stem (avoglios really help here), but you have to really work the heat into stem first. it should not be so hot as to deform or gather, but should be evenly hot all the way through- enough to bend with force if you were to try. heat as much of the stem up as you can handle- you're attempting to mimic a hot shop's glory hole. attach your foot, and immediately start heating the whole foot so it lightly glows. if your avoglio or stem look colder than the foot, reheat them too. paddle your foot straight, then reheat away the paddle chill. lightly flame anneal the whole thing so you can see an even sodium flare coming off each area. it's easy to tell what's colder and hotter by how bright the flare is. as soon as the surface will gather carbon, put the stem and foot in a hot kiln and anneal. later, you can do this same process to attach the cup. if you pull it back out of the kiln hot, be sure to pre heat your claw grabbers.