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Old 07-11-2017, 07:52 PM
Mark Rendulic Mark Rendulic is offline
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Punty Cleanup

I am quite new to glass blowing, and I was wondering how you pros clean up your punty marks. After knocking the part off I have been torching the scar with a mapp gas torch if it looks pretty clean. Otherwise, I let it anneal and knock off as much as I can with a butter knife. Not so pretty. Obviously the goal is to minimize the scar, but what options do I have if I need a little cleanup?
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Old 07-11-2017, 07:59 PM
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Pete VanderLaan Pete VanderLaan is offline
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I grind and polish everything
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Old 07-11-2017, 09:05 PM
Eric Trulson Eric Trulson is offline
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Fire polishing (exactly what you do with the mapp gas) tends to be the overwhelming favorite, because lots of glassblowers hate to coldwork. You can deal with a suprisingly bad punty breakoff on most cups/bowls/vases by torching with mapp gas and then pressing in the punty remnants with the bottom of a spoon. Having a kicked bottom (when the bottom is slightly curved into the vessel interior, instead of being perfectly flat) will allow the work to stand straight even with small punty remnants on the bottom.

Fire polishing is quick and easy and great for production and always looks a bit sloppy. If you really want things to be beautiful, grind and polish. If you are going to grind the work afterwards, you'll generally want to keep the bottom perfectly flat, not kicked.
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Old 07-12-2017, 08:03 AM
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Pete VanderLaan Pete VanderLaan is offline
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One of the things I find interesting about fire polishing the punty is a question of induced strain.

If you put a handle on a piece late in the piece ( known as a seal in the industry), if it is not worked into the piece gradually with reheats, you can see a visible strain in a polariscope where the seal was attached. What isn't clear to me there is whether it's the heat of the attachment or the physical presence of that attachment which causes the retardation to present itself. If it's simply the heat, then I have to question the wisdom of punty torching at the end.

I looked at this stuff fairly hard years ago when making a simple cup and if I just blew the cup, flattened the bottom, puntied, all in one heat and then transferred the cup to a punty and only reheated enough to tool open the cup and then put it in the lehr, I had major strain showing in the bottom of the cup the next day. If I took the piece and gave it a complete reheat after performing the opening and put it away, it showed no strain at all.

So I have to keep wondering about the wisdom of torching the base of the finished work. I've never gotten a cup from anyone who does this and probably should. Fortunately, I like polishing
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Old 07-12-2017, 09:06 AM
Monte Becker Monte Becker is offline
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No matter how you fix it, the less scar there is to start with, the easier it is to clean up. It follows that the long term goal should be to improve the punty technique to minimize the problem. Bill Gudenrath, for one, has a scheme for achieving near perfect results. Plenty of on line video to look at. Best luck!
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Old 07-12-2017, 10:40 AM
Josh Bernbaum Josh Bernbaum is offline
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Quote:
Originally Posted by Eric Trulson View Post
Fire polishing is quick and easy and great for production and always looks a bit sloppy.
Sorry, but I'd disagree about "always" looking sloppy. I think if done right (I think an oxy/prop setup works quicker and better than MAPP) then it can look quite clean. Especially if you follow what Monte just said and the break-off is as clean as possible to start.
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Old 07-12-2017, 05:19 PM
Kenny Pieper Kenny Pieper is offline
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Yep Oxy- propane or natural gas is the way to go. There is no reason that it should look sloppy unless the punty is sloppy.
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Old 07-12-2017, 05:41 PM
Scott Mitchell Scott Mitchell is offline
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Granted I'm just a hobbyist, but have several years under my belt. A clean punty break is still a cause for celebration. I'm getting better, but it is painfully slow.
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Old 07-12-2017, 06:22 PM
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When I work like this, I don't even punty. I blow, knock off and pop the top with a torch on a turntable.Then, being a glutton for punishment, I fine grind the lip flat and then fire polish the lip with a torch and then reanneal it. I would never leave the lip belt sanded. It makes me want to bite off the lip with my teeth. I also grind the base anyway.

I want it to look like it could not be possibly made by hand. The shame. Actually, I do it because I can. There is no way to get a lip thinner by any other process. So ( Scott) if you want that lip where the ice machine breaks the work, I'm trying to get there. Pontil marks ( not punts, mind you , from the French "Pontil" ) are so 1990's. But you're right, no one cares. They should sell for about 150 bucks each. That doesn't go well.

Otherwise, I want them thick enough so you could throw it through a window at a riot and go back for it later. There was a mentality in the '60's in porcelain that made the work so thin that if you filled a pitcher with water, the handle would break off if you lifted it. What a great concept!...The same bunch liked to drive 20 pd nails into finished furniture to make it seem less precious. I think going to a junior college is not a bad idea but I don't think that's what they call them anymore.
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Old 07-12-2017, 07:21 PM
Mark Rendulic Mark Rendulic is offline
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I've been making cups (lots of cups) to learn how to make a consistent size and shape. When I flatten my bottoms I put a slight dent to help it sit flat even if there is a little bump from the punty. I am thinking about picking up a Foredom to touch it up if things don't pop off so smoothly. In the meantime I have access to a Nortel Ranger and give it a blast although I too am concerned with stress. That being said, there is only one way to find out!! I have a polariscope, so I'll make a couple out of clear and see how it looks before I commit LOL!!
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Old 07-13-2017, 11:45 AM
Jordan Kube Jordan Kube is offline
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Quote:
Originally Posted by Kenny Pieper View Post
Yep Oxy- propane or natural gas is the way to go. There is no reason that it should look sloppy unless the punty is sloppy.
I agree with Kenny and Josh. You can make it look like nothing was ever there. Nicer than a cold polish.
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Old 07-13-2017, 12:47 PM
Eben Horton Eben Horton is offline
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I ha e fire polished every piece I have made at my studio for the past 20 years and not once have I lost a piece due to that process.
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Old 07-13-2017, 04:03 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is offline
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I agree with Eben and Jordan- with a oxy-propane or possibly natural gas you can make a perfect bottom. You can pick a bubble out of the side of a finished vase.
The thing with punties is having the right temperature both on the bottom and the punty and then most importantly having a extremely sharp chisel to knock off- blunt things and screwdrivers wont do it- you have to tap right on the joint between the bottom and the punty and you will get a nice puntymark that very fast cleans up with a oxy torch.
Ive never had anything break due to torching- in fact I only know of about 4 things breaking during my whole career- we are talking tens of thousand of things.

Last edited by Michael Ahlefeldt-Laurvig; 07-14-2017 at 01:27 AM. Reason: Sp
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Old 07-13-2017, 05:45 PM
Mark Rendulic Mark Rendulic is offline
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Beautiful!! Thanks for the tips!! I am currently building my own studio and I will run oxy-prop for a torch!! Nobody I work with uses one, so I never considered it. Thought it would cause too much stress, but after hearing from y'all (yup I'm from Texas) I'm no longer concerned. Now I'm off to sharpen my butter knife.
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