Blowing bubbles

Harry · #1 2012-09-08, 6:03pm

I've been trying to blow some small things from 16mm borosilicate tubing. At this point I'm doing okay with pulling points. What I can for the life of me not manage is heat the part of the tube equally well so I get a nice uniform bubble (I'm on a cricket with an 5L/min oxycon). My turning is nice and smooth and I've made a point to let the heat sink in as I heat. Then, before blowing I give it a second so the heat can equalize a little. Still, one side starts bulging, the other barely moves. When I look at the glow before I blow it is pretty much uniform but once I start blowing the bubble ends up wonky. Can anyone explain to me why? I turn the tubing as I blow and I can for the life of me not explain why it's turning out so one-sided.

Harry

houptdavid · #2 2012-09-08, 7:17pm

Quote:

Originally Posted by Harry

(I'm on a cricket with an 5L/min oxycon).

I think that is your answer, I worked my first boro last weekend, all I can say is when you think there is enough heat ADD MORE!

Harry · #3 2012-09-08, 7:23pm

Not sure that's what it is. I've worked a fair bit with Boro and by the time I'm done it is usually hot enough to start flowing if I'm not careful but I'll try heating it more.

H

castaway · #4 2012-09-08, 9:38pm

keep turning as you blow and don't blow too much at a time. B

firefreak · #5 2012-09-08, 9:57pm

Try gathering the glass to half the length you started with. Use heat and gravity. Turn the point to a 45 degree angle to the flame instead of straight across.
example: condense a 2inch section down to 1 inch.
Now go back to straight across and heat the gather as hot as you can control. It should be so hot that it will drip onto the bench if you stop turning for even a second. The hotter you get it the better.
While still turning bring the point up to to your mouth and give it a series of small puffs. push harder as you feel resistance. Don't stop turning throughout. Don't blow hard at first or you will blow out one side. Just small puffs that get harder as you go along. Should take 5 to 7 seconds of puffing to get it blown out to the size you want.
When I teach, I have found that beginners have better luck with extra heavy wall tubing. Sounds like you might be using standard wall. Still usable, you just need to gather a thicker wall for more forgiving try. The wall thickness needs to be near perfect thickness for thin wall tubing to blow out even.
As far as torch goes, I have taught a fair amount of blown boro items ( vases,ornaments, jars, etc) on minor torches. Very do-able, just takes time to get the glass up to proper heat.
The bad news: Once you master this tech, you will be like the rest of us----MUST HAVE BIGGER FIRE!!! LOL

Harry · #6 2012-09-09, 8:39am

Lol, I've wanted bigger fire for a long time but it will have to wait a while longer. I'll try condensing material. Thanks.

Harry

J.Meader · #7 2012-09-09, 10:44am

Don't remove the tube straight out of the flame, keep spinning as you move it slowly to the back of the flame then remove, this will help mimimize the hot spot the blows out first.

Bunyip · #8 2012-09-09, 11:42am

A cricket is plenty HOT enough, but I bet it's a lot of work to get it spread out evenly enough in the glass. You'll probably learn a lot though!

menty666 · #9 2012-09-09, 2:05pm

Quote:

Originally Posted by firefreak

Try gathering the glass to half the length you started with. Use heat and gravity. Turn the point to a 45 degree angle to the flame instead of straight across.
example: condense a 2inch section down to 1 inch.
Now go back to straight across and heat the gather as hot as you can control. It should be so hot that it will drip onto the bench if you stop turning for even a second. The hotter you get it the better.
While still turning bring the point up to to your mouth and give it a series of small puffs. push harder as you feel resistance. Don't stop turning throughout. Don't blow hard at first or you will blow out one side. Just small puffs that get harder as you go along. Should take 5 to 7 seconds of puffing to get it blown out to the size you want.
When I teach, I have found that beginners have better luck with extra heavy wall tubing. Sounds like you might be using standard wall. Still usable, you just need to gather a thicker wall for more forgiving try. The wall thickness needs to be near perfect thickness for thin wall tubing to blow out even.
As far as torch goes, I have taught a fair amount of blown boro items ( vases,ornaments, jars, etc) on minor torches. Very do-able, just takes time to get the glass up to proper heat.
The bad news: Once you master this tech, you will be like the rest of us----MUST HAVE BIGGER FIRE!!! LOL

^This. If you're being really good about heat base and you're still getting an uneven blowout, you need to focus on the wall thickness. It's easier to thicken it up a little to give some wiggle room than to eyeball a thinner wall and hope for the best.

The cricket's fun, but I still tank it instead of running on my single 5 lpm machine. It just works better that way.

Harry · #10 2012-09-09, 7:49pm

I just tried it with more heat on a piece of tubing that was too short to pull a point. It looked much better. What is going to be the problem is to keep the turning constant with both hands once the material is so soft or you get a spiral in the glass. Well, I guess that's where the practice comes in, otherwise it would be easy.

Harry

firefreak · #11 2012-09-09, 10:09pm

If you got one to look better, your already on the way to mastering this part of blowing tubing!
Try giving the point a very small puff every so often as you see it condense. You don't want it it to blow out, just bulge a little bit. The pressure causes the wall thickness to even out. Thin and thick spots in the gather make it easier to twist. It really is easier to blow out a small thick ball of glass. And easier to control a thick gather.
A good exercise for even turning is to find a piece of 7 mm rod about 14.inches long. While you are watching TV or some other low concentration activity, turn the rod in both hands as smoothly as possible. For as long as you can. First one way, then the other. First with dominate hand, then switch. Feel the drag on non leading hand? That is why your soft piece was twisting! ( remember that, you can use it later) When you don't feel the drag, your ready to do it with hot glass.
Reading the temp of the glass and smooth turning are basic tubing skills we all had to learn the hard way. There are no short cuts that I know of. You will develop muscle memory to the point that you don't have to think about in short order. It always seems like it shouldn't be that hard to learn a new tech. And it's not, as long as you practice, practice, practice.
Welcome to tubing 101. 201 is single handle point. 301 is 9 to 12 mm blow pipes attached to sections of tube. then bigger tube, than bigger torch, then---------

khan · #12 2012-09-10, 8:54am

Ill tell you what i was doing wrong when i had the exact same problem. I cant say for sure your doing it but i bet you are.
When you remove the glass from the flame and begin to blow if your two hands are not perfectly in line with each other and you have a slight bend in the glass then the side that is bent out will come out first. Now ppl say "keep turning" and one main reason for that is because if you have a slight bend then it should even out as you turn. But seems to me that once it starts out on one side turning will not always even that out...and its because your hands are not in perfect line with each other.
Another thing is if you are slightly pushing together with your hands it makes the whole situation much worse. Because now the side that is bent out just slightly is being held length wise and the glass has to go somewhere so it goes OUT.
What i did to fix it....
i made it a point that when i start my blow to not only keep turning but also to slightly pull my hands apart.. That seems to keep them in line better and it gives the glass somewhere to expand lengthwise. And damn it made all the difference in the world.
Just a slight pull apart and i promise they will be easier to control.
I just struggled with the exact same problem for weeks. And i almost bet that is your situation.
When i was blowing using a point i would get better bubbles but i wanted to learn to use a blow pipe. When i used the blow pipe is when i got the problem. The reason is because when your looking at it from the side using a blow pipe it is much much harder to tell when things are in perfect line. When you look from the end as when your using a point it seems easier to get things lined up and its more natural to give that little slight pull that is needed. So i had to make a spicific effort to remember to pull just a little when i went to using the blowpipe and that lined things up for me.
I hope all this made since to you. Im sure it will help you if you can follow what im trying to say.
Best wishes.

Khan