punty up and...crack.

[menty666]

I've been trying to make vases and often when I punty to the bottom to finish the top (remove it from the point, etc) I wind up with a crack in the bottom instead.

what the hell am I doing wrong?!

It drives me nuts to spend time laying color, trying to get the shape right only to have it go tink on me.

[The Glass Fish]

If it is a point that I think I can clean and open fast, I don't use a punty, I use hotfingers. If it will take longer, or I want better control, I will punty. A good cold punty deliberately puts a small amount of stress at the point of contact, allowing easy removal. Make sure the bottom has a good base heat first to buy you some time. then, if the top takes too long garage it before you remove the punty. It is also possible that your cold punty is too good. If the glass was too hot, the affected welding area will be deeper, and the stress will be deeper. You want a punty that will hold, but not such a deep weld that it cracks from stress. That balance just takes practice.

When I apply a cold punty to hold a piece I quickly attach it while the tip of the rod is hot and then I very quickly Rotate the rod back and forth, wiggle it up and down, then give it a little tug. This pre stresses the weld on the surface and helps get it centered. Usually it tinks off only when I want to without cracking. Hope this helps.

[lucidvisions]

Hey buddy, you're not alone on that one. I've always had issues with that. Now I just use the grabbers to hold the bottom of the vase and blow and flame cut the top and then flare (if needed). Another way I've had success is to make sure the bottom of your vase is slightly concave. Make a seal that is fully attached with no angles in the mmiddle of the bottom of the vase. Then do what you do to open the vase. When done, grab the top of the vase with grabbers and just flame cut the punty and remove excess glass until vase sits upon it's edges.

Hope it helps.

Josh

[Mr. Whale dick]

^^^^

what he said...

grabbers, or a fully fused dot on the concave bottom(so if it does crack it's just the punty to the dot not the piece)

or let the top cool and just stick the bottom 1/2 in the kiln (make the top 1st)

[nicko0]

finger holders when possible but i find i can flash fire around the cold fused punty until a little heat is built up then tap it. this seems to work pretty well for me. on large pieces like vase size i usually punty up too strong (for fear of accidentally tapping it or i need to push on the piece) and have to flame cut the punty off and heat and flatten then melt in until smooth or gather it off if its on an exposed end. for me if it wont come off with a light tap(relative to what) i flame cut.

[VOORHEES]

I put a dot on the bottom, melt it in al the way and punty up to that...I rarely crack them when I do it like that.

[menty666]

thanks folks. If nothing else it's nice to know I'm not the only one thhat has issues with this.

[jiminyrootkit]

hotfingers.
if that doesn't work, get another size of hotfingers.
this strategy developed through my inability to remove a punty from thin hollow work without cracking it ;)
-f

[matte eskuche]

Mr. Menty,
there are way too many variables in coe, colour, size, weight, shape, etc. to figure out what approach to take to succeed with your pieces utilizing punties, but all in all, you can get away with a punty in many circumstances before the claw tool becomes a necessity.

a sure way to crack a piece through the use of a punty is if it has a flat bottom, other than that, practice at a small scale, indent the foot of the vessel, attach the punty with only a small amount of the puntie's surface area heated, flash repeatedly, flash heat at the punty connection until it moves slightly just as you attempt to knock off the point handle before flaring the top open.

you'll have a ton more control over the piece when it's on a small diameter rod or point handle as a punty than with an unwieldy claw tool. the claw tool weighs more, keeps your hand further away from the piece, allows the vessel to slip out of center, etc. etc.

practice a bunch with punties and you will benefit a thousand times more in learning about the glass than with a claw tool.

i had a student last summer who never tried hollow work before, only soft glass beads. she struggled all week with tiny vessels finished on a punty. several pieces that had taken her half the day just get shaped were cracked by the punty. at the end of the week she finally pulled off a finished piece knocked of a punty.

then i showed her the the crappy claw tools they had in the tool boxes. she was totally pissed for a second that i hadn't shown her that tool the first day. now she makes nice little scent bottles with little handles and different shapes and openings and all on a punty.

sometimes i use an analogy my father used on me as a child. he referenced driving a car (go cart at the time) as fast as you can through the corner, spinning out, and taking it a tiny bit slower each successive time until you are going through the corner as fast as possible without spinning out. or you can go through the corner slowly and safely, then up your speed each successive time without ever spinning out until you are going through the corner as fast you can without losing control. the first option teaches you the most about the threshold of speed through the corner and is similar to the punty teaching you the most about the threshold of the material. the second only gives you an idea of the threshold, similarly the claw tool gives you merely a crutch to reach a finished product, and teaches you absolutely nothing about the material.

the analogy works the same in referencing the use of a kiln to garage as opposed to flame annealing and learning to bring the work out of the flame without stress so that a kiln is largely unnecessary.

holy long post, too hard to explain without conversation and equipment to try out out on.

[menty666]

I'm definitely a bit hesitant about the hot fingers and I've had a few ornaments go springing out of them and onto the back of the bench before, so the punty method is more appealing.

I'll try putting a kick into the bottom with an extra little bleb just for the punty connection. That way even if there's a slight sharp spot it's not right out where someone's going to get hurt.

I'll almost make sure there's a little extra heat in the bottom before I connect, there's a good possibility that the bottom is simply too cold when I put the punty on (though I do give it a little heat to make sure the rod's connected.

All in all I'm sure it's one of those practice practice practice scenarios.

Thanks folks!

[lucidvisions]

If there's any advice you should probably follow it would be Matte's IMO. I know I will. Time to head to the go-cart track!

Josh

[schmoinkel]

That is some great advice and well put too.

I went for a ride around the track this morning...ended up in the bleachers!

Gonna go give it a few more tries.

Scott

[Icarus]

Just to clarify Matt's post, never drive a go-cart at high speed through a turn while holding a hot punty. It will only lead to heartache.

Good post Matt. Thanks for the help.