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  #1  
Old 2010-08-21, 1:54pm
Kurt_ Kurt_ is offline
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Default Borosilicate tubing always cracks on me.

Hey all. I'm relatively new to lampworking. I am self-taught (trial and error), and have been making borosilicate pipes for about a month now.

A gigantic problem I have been having is that everything always cracks on me.

Let me elaborate, here's my current technique:

1) Pull a point
2) Pour frit in to tube
3) Seal end, blow out into a bulb
4) Melt frit on to the inside
5) Add twists, bulges, etc to the pipe shaft.
6) Pop a hole for the bowl/carb, and make the bowl.

But here's where the problems begin. When I go back to the point to create a mouthpiece, it usually ends up cracking off. I never had this problem so often before I used frit.

Not only that, but after the pieces cool, they develop a few cracks. (I usually air-cool then bring up to annealing temperature in my kiln)

And as if THAT wasn't enough, when I try to repair the cracks by bringing the borosilicate art piece up to 650 C, and reintroducing to the flame, it just starts cracking more when the flame touches it, as if I didn't preheat it at all.

Now, I should note that I do like adding twists, and this may or may not contribute to the cracking.

Here are some examples.

This one worked out perfectly, except it has one small crack where the bowl meets the shaft (Likely a difference in thickness)

http://yfrog.com/n6earth012j

---------------
This one cracks lengthwise from the black head. I repaired all the cracks, but after cooling, it had cracked again.

http://yfrog.com/n1parasite011j

I'm probably missing some elementary knowledge. Don't leave anything unexplored.

Last edited by Kurt_; 2010-08-21 at 1:56pm.
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  #2  
Old 2010-08-21, 2:09pm
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Kurt,
Don't feel bad..........I've been having the same issues and I'm not using frit. Nothing like being a newbie..........lol
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  #3  
Old 2010-08-21, 3:23pm
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Just looking at those pictures I can tell you a couple problems...

1. Your frit doesn't look like it's melted all the way in on the inside
2. Green doesn't work well inside
3. Don't let them air cool. At least use some vermiculite or fiber blanket. The air cooling only amplifies the frit not melted in problem.

Try melting the tube down and blowing it back out a couple or three times when melting the frit in. They are probably cracking while they are cooling and you just can't see it until it goes into the kiln. You should put pieces directly into the kiln after you work them.
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  #4  
Old 2010-08-21, 3:31pm
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What Cosmo said...

I'll add that you need to keep the mouth piece hot as you work on the bowl end... Just add some insurance heat every once in a while... flash, work on other end... flash, work on other end... rinse and repeat.
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  #5  
Old 2010-08-21, 6:10pm
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Why doesn't green work on the inside? (It's Northstar's Jade, by the way)

I guess my problem is that I pay a lot of attention to the bowl end when making it, neglecting the shaft.

As for flashing, how do you recommend I flash something like this? Should I get it red hot, or will something below the melting temperature be just as effective? Should I do a quick once over (Which I tried, and it just lead to cracking, so I guess I need a better method) or should I let it heat up for a few seconds?

As far as the frit not being melted in, I know. I've been working on that. It takes some practice to keep the tube from stretching, folding, or collapsing.

I worry that since they crack when reintroduced to flame, if I put them straight in a hot kiln, they'll crack. Am I right? Can anyone recommend a temperature to have the kiln at just for colder pieces before annealing?

Rather, I guess if I flash it enough, I could just pop them in to a 565 C kiln. Am I right?

Can anyone see any other problems? Tomorrow or Monday I will have some specific problems for you guys! And thank you for the help. Really. There's not many people I can turn to for help with things like this. Sorry I type a lot.

Last edited by Kurt_; 2010-08-21 at 6:20pm.
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  #6  
Old 2010-08-21, 6:40pm
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Just bring it back to a slight glow... when ever you do inside work, you've got to keep it warm or it'll crack... you'll find a groove... you can also pop it into a hot kiln to warm it back up before you go to the mouth piece.

Nope, if you put them into a hot kiln, it'll save 'em... it's so much better than air cooling... like light years better.
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  #7  
Old 2010-08-21, 8:13pm
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I'll offer a different opinion...

I don't go back and flash the mouth piece end while working on the bowl. But, what I do when it's a color that is questionable or if I'm worried about it for whatever reason, I work the bowl and everything up until I'm ready to do the mouth piece, then put it in the kiln and let it soak. Work on another piece for a little bit, then come back and finish the first piece.

By the way, what size tubing are you using? That looks like pretty thin wall. I'd start off using something like 25x4 or something to start off with. You get more depth with thinner wall tubing, but it's harder to use until you get the hang of it. Thicker wall is more forgiving.

Jade is notorious for cracking on the inside of pieces. I would stay far away from it. If you really want a green color that is stable, get some Amazon Night. To make sure your frit is totally melted in, heat the piece, shrink it down, blow it out, then shrink it back down before shaping it. The expansion and contraction helps everything melt smooth.
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  #8  
Old 2010-08-21, 8:49pm
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I should note that I am working outside. I try not to do anything when a breeze blows by, and I'm partially sheltered from wind. I work with what I can get. Also, it would be virtually impossible to keep everything glowing a slight orange and still do work on the bowl due to the size of the pieces, and the size of my flame (It can only get about 3/4" wide, it's an oxy-propane cutting torch attachment for an oxy-acetylene torch. It's served me well thus far.)

What's a good soaking temperature? This seems like a method I can agree with, but 650 C didn't seem to be hot enough. I could probably get my kiln up to about 800 C if I tried. But then I worry about adding cold pieces in to it. Wouldn't they just crack, going from 30 C to 650 C near-instantly?

As for tubing, I'm using 22 x 2.5mm for these pieces. They look a little thin in the pictures, but they're not. Narrowing to as small a hole as possible then widening is what us engineering students call a diffuser, in the most basic sense. It cools the smoke and reduces its speed for an easy, smooth draw. The twists gives the illusion of thin walled tubing, but I assure you, It's at least 2 mm everywhere. It's the thickest I can get without getting a large diameter tubing.

If the glass anneals at 565C, max 600 C, I read that for fixing cracks it should be 100 above this, 650 C. But this didn't work. What should I try? 750? 800? What do YOU use?


Again, thanks for all the input. I'll give everything a try the next chance I get.

Last edited by Kurt_; 2010-08-21 at 8:55pm.
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  #9  
Old 2010-08-21, 9:08pm
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22x2.5mm tubing is too thin and too narrow. You'll make things that work, but they wont really be pretty. You should try and work on 28mm-38mm in that range and medium wall on up.

Your frit is mostly melted in, but your really stressing the clear glass with so many twists and turns. Those also have to be re-melted in too. Just blow out the glass a little to keep shape and maintain the white heat till its fused properly.

When you bring the pipe back into the flame from cold, toss it in the kiln first then pre-heat with a soft-bushy flame then go flame crazy after about 30 seconds to a minute of pre-heating.

Hope this helps, it sounds weird typed up. There arent many pipe makers on this site, I'm one of the few and brave too so if you have questions.....
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Old 2010-08-21, 9:11pm
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By the way, what type of setup/torch do you use?
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  #11  
Old 2010-08-21, 9:27pm
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Hmmm... Re-melting the twists would probably help a LOT. But I have one pipe I made today that keeps cracking from the choke, even after I repair it.

My setup is pretty ghetto, and difficult to picture. I'm using a victor welding torch with a #2 propane cutting tip. It's not meant for glassworking, but it does the job just fine (it could be a little wider of a flame, though). I chose this because I can also use it for brazing/cutting/welding, since I jump hobbies every few months. Lampworking just might stick though.

http://www.youtube.com/watch?v=Zv7YuDcYp2E

Roughly, that's what I'm using, except at much lower pressures (Oxygen 7.5 PSI, Propane 4 PSI). It's mounted to a workbench.
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  #12  
Old 2010-08-21, 11:53pm
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if you want to be good at tube work it is best to learn on the thinnest tubing available. if you can master thin wall, then other thickness tubing will be cake work. it's just a thought. and no I cant work thin wall well.
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  #13  
Old 2010-08-23, 5:12am
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Quote:
Originally Posted by Kurt_ View Post
I should note that I am working outside. I try not to do anything when a breeze blows by, and I'm partially sheltered from wind. I work with what I can get. Also, it would be virtually impossible to keep everything glowing a slight orange and still do work on the bowl due to the size of the pieces, and the size of my flame (It can only get about 3/4" wide, it's an oxy-propane cutting torch attachment for an oxy-acetylene torch. It's served me well thus far.)

What's a good soaking temperature? This seems like a method I can agree with, but 650 C didn't seem to be hot enough. I could probably get my kiln up to about 800 C if I tried. But then I worry about adding cold pieces in to it. Wouldn't they just crack, going from 30 C to 650 C near-instantly?

As for tubing, I'm using 22 x 2.5mm for these pieces. They look a little thin in the pictures, but they're not. Narrowing to as small a hole as possible then widening is what us engineering students call a diffuser, in the most basic sense. It cools the smoke and reduces its speed for an easy, smooth draw. The twists gives the illusion of thin walled tubing, but I assure you, It's at least 2 mm everywhere. It's the thickest I can get without getting a large diameter tubing.

If the glass anneals at 565C, max 600 C, I read that for fixing cracks it should be 100 above this, 650 C. But this didn't work. What should I try? 750? 800? What do YOU use?


Again, thanks for all the input. I'll give everything a try the next chance I get.
I soak my pieces at 1000F. Not sure what that translates to in celsius though.

I wouldn't go over 1050 for hollow pieces or you risk slumping them. I ramp my kiln up to 1150 to strike colors, but only hold it there for 10 minutes.

Try some larger, thicker tubing. Also, try some just plain clear pieces. Get those down to where you can do them no problem, then go on to wrap and rakes. That will give you decent looking pieces, but you don't have to worry about the frit on the inside. Once you get the hang of it, then go back to using the frit.
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  #14  
Old 2010-08-24, 3:32am
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1050 is 565 degrees

#and 1150 is 621 degrees celsius

i think

i garage at 537 and ramp up to strike my colours at 630 or something like that

has somebody a cool annealing /striking cycle i can use even to warm up the pieces, my cycle works so far but i think i could be programmend better
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Old 2010-08-24, 6:26am
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Great advice on not flash warming the piece .... as long as everything is melted in really good you have a lot more time doing other things to it then you might think .... I also do what Cosmos does and soak after doing the bowl for about 15 then come back out and finish the mouth piece ... GL!
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Old 2010-08-25, 10:03pm
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I shape the mouthpiece before i shape the bowl.
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Old 2010-08-26, 5:03am
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Quote:
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I shape the mouthpiece before i shape the bowl.
Do you remove it from the handle or just get it in shape? I've seen some people remove the handle and then punty up with a blowtube, but that looks like way too much work for me.
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Old 2010-08-26, 6:55am
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sometimes i work the mouthpiece first down to being ready to take it off the handle (thin pull) then work the bowl area... that way you can go in with a small flame to take the handle off when all is done, less chance of cracking mouthpiece...
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Old 2010-08-26, 7:42am
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To answer one of your other questions, greens are laced with metal (chromium was it?) and cool at a different rate than the clear, so working them inside creates enough extra stress to crack the glass.

I only know of one that you can deep encase, and even then I do it very thin.
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Old 2010-08-26, 2:37pm
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Quote:
Do you remove it from the handle or just get it in shape?
Most spoons i do are done in one shot no reheating in the kiln, no handle switching.
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  #21  
Old 2010-08-26, 3:56pm
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So far, so good. My kiln is giving me some trouble (Maxing out at 440 C), but other than that, I had a successful day, making 7 pipes (on 2 of which the heads broke off) in 4 hours, 20 minutes. The time it took was pure coincidence.

I also managed to repair the cracks on four pipes I had made previously. Everything is still cooling, but I feel good about today's harvest.

Maybe it was all the wonderful advice, or maybe it was the first edition holographic Charizard (with four fire energies, of course) that I brought out for good luck.

Earl: That tip is an excellent one, sure to save me a lot of potential grief!

Pictures coming... eventually.
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Old 2010-08-27, 2:52pm
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Quote:
Originally Posted by Kurt_ View Post
So far, so good. My kiln is giving me some trouble (Maxing out at 440 C), but other than that, I had a successful day, making 7 pipes (on 2 of which the heads broke off) in 4 hours, 20 minutes. The time it took was pure coincidence.

I also managed to repair the cracks on four pipes I had made previously. Everything is still cooling, but I feel good about today's harvest.

Maybe it was all the wonderful advice, or maybe it was the first edition holographic Charizard (with four fire energies, of course) that I brought out for good luck.

Earl: That tip is an excellent one, sure to save me a lot of potential grief!

Pictures coming... eventually.
Your kiln is way too cold. You aren't annealing at all, just avoiding thermal shock at best. Your kiln needs to get to 550 degrees celsius, with even 540 degrees celsius being dangerously low.
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Old 2010-08-27, 5:46pm
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A quick note that I didnt mention before to help on mouthpieces cracking........ Heat the area before the mouthpiece that's still the clear tubing instead. That way if it cracks, it cracks there, not down the whole neck of the pipe you just spent a half hour making. Does it make sense? If not I can try to reexplain, just hard since right now it's 8:40, which, coincidentally is twice as high as 4:20.
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Old 2010-08-27, 7:52pm
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Here's a question for you guys. I hope there's an easy answer, but I might be out of luck.

My kiln is a homemade propane kiln. It runs off of propane and forced air. The flame is, no matter what I do, a reducing flame.

Now, I got my hands on some Loki's Lipstick rod, and I don't like it when it's reduced. I want to strike it, but it doesn't seem to work.

However, striking ruby in the kiln works just fine, so it's probably only slightly reducing.

Is there a way to oxidize colours without a kiln? I would also like to avoid using the direct flame, on account of all the cracking.
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Old 2010-08-28, 7:26am
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I'd try some fiber blanket or vermiculite to cool your pieces, and then maybe once a month or so find someone with a regular electric kiln that will anneal your pieces for you. If you use vermiculite, be sure to wash the piece very, very well with water before you use it though.

Plus, with a propane kiln, I imagine there would be a big variance of temperatures inside it, which would only add to your cracking problem.
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Old 2010-08-29, 4:31pm
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Well, it's a big kiln. It's kind of like an oven. I tried annealing today, and I have to say, it worked out pretty well. Apart from a few short cracks, everything is intact.

What would you guys suggest for an annealing program for these guys? I have this chart that says to hold at the annealing point for 15 minutes (1050 F), take 10 minutes to bring down to the strain point (950 F), hold for 3 minutes, and cool to room temperature over 14 minutes.
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Old 2010-08-29, 6:33pm
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That's way too quick of a ramp down. They are only in the kiln for less than an hour.

I hold at 1050 until I'm done then hold 1 hour at 1050 after the last piece goes in. Ramp down to 960 at 60 degrees/hour, then down to room temp at 300 degrees/hour.
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Old 2010-09-01, 9:47pm
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I simply don't have enough free time to cool it that slowly in the kiln (as it's all manual, no fancy controllers to program and forget about). Is there an alternative method that is a little more... creative?

For example, keep the pieces for an hour at annealing temperature. Put the pieces in a container full of vermiculite IN THE KILN (1050 F) and then turn off the kiln.

Another idea is using ashes. We heat the house with both a gas furnace and a wood stove in winter, so I have TONS of ashes. I remember my dad covers the embers with ashes, and the next day there is sometimes enough embers still hot enough to catch paper on fire to start another fire the next evening.

Would this cool them slowly enough? I just spent $8444 on tuition. I have no job. An electric kiln is way out of my price range, and nobody around here has one I can borrow.

Last edited by Kurt_; 2010-09-01 at 9:51pm.
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  #29  
Old 2010-09-02, 6:24am
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That may work. Not having tried it I can't say for sure though.
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Old 2010-09-02, 11:36pm
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Try making several clear ones with that annealing method then check for stress with a polariscope. If need be you can make an extremely cheap polariscope with an inexpensive pair of polarizing filters for a camera lens or even a cheap pair of polaroid sunglasses.
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