Cracking Off

[KyleJamesRichards]

Sounded like he said jacking off

[ozzyscruggs1]

Wonder if I couldn't drill holes in glass panes with this? Use a lathe faceplate or similar fixture to turn the glass on a horizontal axis while pointing a torch flame at it.

Very cool demo, definitely gets your attention when the glass cracks dead on in a circle.

[harmonicgrunt]

the best i have seen.

[missplumeau]

Thank you for posting this very understandable video! I have been looking for ways to do this for a long time. I tried the "string" method that made a very ugly cut. Thank you!!!

[willyreed]

thank you so much for this wonderful instruction.

i have tried it on wine bottles that i want to make into drinking glasses and i have 2 questions; i'd be grateful for any reply.

1. the bottle does not cut evenly - that is flat, or perpendicular to the bottle's long axis. how can i fix this?

2. what is the best way to make a nice smooth lip from the cracked rim? easy way?

thank you very much!

[corningmuseumofglass]

There are many things that can cause the rim to not break evenly, including turning too fast, turning too slow the flame being to broad, or bushy, and more. Be sure you flame comes to a point, and that you don't hold it too close to the glass. You should see the blue point while heating.

[ozzyscruggs1]

You don't think the glass carries internal stresses from being unannealed?

[corningmuseumofglass]

@ozzyscruggs1 the thicker the glass, the more stress remains from the cracking off process. The glass is annealed originally after it is blown, and that lack of stress is one thing that allows the glass to crack off so perfectly. The stress in general pales in comparison to the stress of being firepolished (where the same flame heats he glass until it softens and surface tension pulls it round and smooth). If you were not cold working the rim, i would re-anneal it for safety.

[corningmuseumofglass]

CONTINUED- Turn fast enough that the flame never pauses on one area for more that a tenth of a second. Try a little slower and a little faster if you're having trouble. For the lip, use wet dry sandpaper to remove the sharp edge, but finishing it very smooth will require some more serious cold working, with a machine or much hand working.

[juventus86]

@willyreed also, this works best with a very fine flame. If you are using a standard plumbers propane torch the flame is too large. A small jewelry torch works very well

[azeromedia]

Thank you sooo much for this great video! I am gathering all the tools, and just wanted to know...do I need a "diamond" cutter as they are quite expensive. I have a normal bog standard, glass wheel cutter. All the bottles ready to go!

[corningmuseumofglass]

all you need is a definative and visable scratch. The glass cutter may work, a carbide lathe tool head would work. Try it. If the cutter doesn't work just google diamond scriber, and you can find many option for under 20 dollars.

[bazzarr]

This is amazing. After watching the video I decided to try this for myself with stuff I have laying around the house. I got myself an old wine bottle, a dollar store carbide hacksaw and a cheap bernzomatic butane torch from Home Depot

Using the hack saw, I scored the wine bottle in one small spot  and then placed it in my kitchen sink spinning it slowly while heating the circumference with the torch. After about a minute -CRACK- the bottle snapped all the way around and separated!

[lizcrrr]

how about that heating. i don't have a fancy heating tool nor a turntable. can i do that above a candle, rotating it myself? won't probably be as straight. but does the speed matter? cheers.

[corningmuseumofglass]

The speed does matter, too slow overheats one area excessively, too fast and the glass skin doesn't absorb enough heat. The turntable could be a cake icing turntable. The torch is a butane powered torch from the hardware store.  A candle may not be a consistent enough heat source. Even a plumbers torch would work.

[goldfishvt]

Thanks for the great cracking-off video & tips! 2 questions: 1) will this technique work for thicker glass (1/4" to 1/2")? 2) Should the glass piece be annealed in a kiln after applying the cracking off method? many thanks!

[corningmuseumofglass]

1/4, absolutely, 1/2, yes, but it will require a hotter torch, but still one with an acute flame. It also takes much longer. As the glass gets thicker, yes, re-annealing would be a prudent measure.

[monkeysthrowingpoo]

can you use this to make a hole through a bottle too?

[LiqweedFTW]

lol if you want to make a glass bong you should buy a diamond tip drill ;)

[monkeysthrowingpoo]

ha i know that shits expensive tho

[LiqweedFTW]

yeh thats why i make plastic ones --_-

[as200s]

do u need to use a diamond tool?

or will any tool that makes a scratch do

[telempemori]

Where do you get a diamond tool like that and how much do they cost?

[sublimationman]

That is a standard diamond glass cutter from any hardware store. $5 to $10