Use Grozing Pliers & Running Pliers to Break Glass

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Use Grozing Pliers & Running Pliers to Break Glass

​How to use Grozing Pliers & Running Pliers to Break Glass

Breaking glass to the perfect shape needed to fit your glass pattern can be quite tricky at times. But, if you know which pliers to use, when to use them and how to use them properly, creating with glass will become a whole lot easier.

Cutting glass into specific shapes not only takes knowledge of how to score and break glass, it also requires strategy. You have to plan your cuts strategically and also use the right tools for the job.

Since there are so many things to consider to make the perfect break, and things can often be overwhelming early on in this hobby, I'd like to break down the cutting process and just focus on one aspect that you may be struggling with.

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​Breaking Pliers: Which Ones To Use

​So you've planned your cuts, made your first score  and ​reach for your pliers. But which ones do you choose? 

I've seen ​​hobbyists struggle​ with this many times over and it's as though ​​they were put on the spot to diffuse a bomb. It's written all over their face,"Do I cut the blue wire... or the red wire..." And they freeze.

​Instead of feeling this way, lets discuss:

  1. ​The most commonly used tools ​for breaking glass
  2. ​Wh​at they do
  3. ​Which ones you should use for each kind of break 
  4. ​How to use them effectively

Personally, I use 3 sets of pliers ​although​ hobbyists​ will likely only need 2. ​

​1. ​​Running Pliers

​First of all, the running pliers ​used to break glass are available in different materials; plastic or metal. I've tried both but only recommend using the metal ones. My personal favourite are the Leponitt running ​pliers with 8" handles.

​You'll find out shortly after you get into making stained glass, that running pliers are the friendliest ones to use. They're great for long and straight or slightly curvy ​breaks and​ for short​ straight breaks too. They often become your go-to pair ​of pliers when you're starting out.

​How do running pliers work?

Understanding the mechanics of how running pliers work will help you determine when they are best used. ​These pliers have an adjustable set screw ​which should almost always be facing up when the pliers are​ in use. The screw creates a stopping point ​preventing too much pressure ​on the glass while squeezing the handles.

When seen from the tips head on, you​'ll notice that both jaws curve the same ​direction. The reason for this shape is so that ​when​ ​glass is placed between the jaws, the bottom jaw ​pushes up in the ​center directly under the score while the ​outer edges make contact with the top of the glass and push downward. Since the score line is placed in the center, the running pliers create enough leverage ​for the glass ​to break.

The break starts where your pliers are and then it travels or "runs" the length of the score.

How to ​Use Running Pliers

  1. Make sure ​the score doesn't have wicked curves, as running pliers are most effective on straight or slightly curvy shapes.​
  2. ​Hold the pliers with the ​shape of the tips low on the outer corners and higher in the center. (​Remember to add some little eyes with a marker or glue on googly ones for fun!)
  3. ​​Adjust the set screw as shown in the video below.
  4. Place your scored piece of glass into the jaws of the pliers with the handles ​at the same angle as your score line, no further in than half​ an inch.
  5. Squeeze gently. When the set screw has been ​properly set and you made a solid score, the glass will ​break quite easily. If not, try starting from the opposite end of the score.

** Note: The little rubber covers on the tips ​should not be removed. They are there to prevent the pliers from crushing, scratching or chipping the glass.

​2. ​Standard Grozing Pliers

​​Don't ​let these small pliers fool you! They ​actually do a whole lot to help you with your glass cutting. When you're still new to the craft, grozing pliers aren't quite as "user friendly" as the running pliers. But once you're comfortable using them, they open up a whole new world for getting good breaks.

​Grozing pliers are great for snapping off little pieces; be them really ​narrow ​pieces or little notches inside a curve. Cleaning up after running pliers if there happens to be a little chip left behind is another great way to put your grozing pliers to work.

How do ​Grozing Pliers work?

​When ​viewing grozing pliers​ from the side, notice how ​one jaw is flat while the other is curved? The flat jaw is the one that goes on top of the glass. Again, if you have a hard time remembering, just add some little eyes as a reminder ( just like you saw in the video above about running pliers.)

​​Grozing pliers are used with the flat tip butted against your score line, unlike running pliers.

Many people find these pliers ​challenging to use​ generally as a result from a lack of understanding of what exactly one's supposed to do with them. So let's break it down step by step.

​How To Use Grozing Pliers

  1. ​Unlike​ running pliers, grozing pliers are used with the flat tip butted up against your score line.
  2. ​Squeeze the pliers until you have a firm grip of the glass but not so hard that you crush it. Maintain this pressure throughout the rest of the directions. ​​
  3. ​Get a steady grip on the glass with your free hand.
  4. ​The method of breaking the glass with grozing pliers is by pulling the piece of glass off of the rest. ​Watch the video clip below to see how it's done.

​3. Narrow Tip Grozing Pliers

​These pliers aren't an absolute necessity but once you start working with more intricate curves, you'll find them to be super convenient​ to have in the drawer. 

​When viewed from the side, the narrow tip grozing pliers have a flat jaw on top and curved jaw on the bottom. Butt the tip of the pliers against the score line to make the break.

​These narrow grozing pliers are used when ​standard grozing pliers are too wide to fit ​the piece of glass ​being removed. Because you ​need to stay just be​hind the score line and never cross it, there ​will come a time that your standard grozing pliers are simply too big for the job. That's when ​​most people invest in a pair of the narrow tip grozing pliers.

​How To Use Narrow Tip Grozing Pliers

  1. ​Place the tip of the pliers against the score line.
  2. Squeeze the pliers until you have good grip on the glass and maintain this pressure. ​Be mindful that the narrow tip makes it slightly easier to crush the glass than with standard grozing pliers, so be careful.
  3. Get a steady grip on the glass with your free hand.
  4. Pull the tiny piece of glass away from the rest. ​​Watch this technique in action​ in the video below.

​How To Practice Breaking Glass

​So now that you know how to use your pliers more eff​ectively, you need to put this knowledge into practice. My suggestion​ for you is the following:

  1. ​​First, locate the top of each pair of pliers. Use your marker or add some googly eyes​ to remind you which way is "up" ​if you need to.
  2. Using some scrap glass (preferably something smooth), start by marking off the corners at ​ a half inch or just over a centimeter. Score them and then use your grozing pliers to "pull" the corners off.
  3. Next, draw a couple of lines across the glass. Score them and practice using your running pliers. Don't forget to adjust the set screw as needed. (You should do this for each new type of glass you are breaking.)
  4. Assess how well you did.
  • a) If everything worked well, pat yourself on the back! You did it! But don't stop there. Repeat the process right away so that you reinforce the skills you just learned and become a little more confident with what you're doing. That way, the next time you pick up your tools you'll have a better chance of remembering how you used them. And, you'll also have that little confidence boost of knowing that you've already done it more than once, so you know ​you can do it again.
  • b) If things really didn't turn out as planned, try watching the videos again. Sometimes watching the same task performed a few more times is all you need to see where you went wrong. When ready, start these practice steps ​again and give yourself ​a little more time to think each step through until you nail it.

Learning​ is a process which takes time. ​To see improvements in your glass skills, you need to put in the time to practice.

Making stained glass has so many steps and there are many more little steps within each of the big ones. By breaking down​ instructions into manageable chunks I've been able to help hundreds of local ​hobbyists in my studio learn these skills. ​You can ​learn them too.

You've got this!

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About the Author

Samantha's a passionate creative with varied artistic interests which she loves to incorporate into her glasswork. Working in both stained glass and fused glass, her goal is to help you be creative and think outside the box while teaching skills to make glass crafting easier.

Samantha Calder

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  1. This was excellent! I have been doing stained glass for 12 years, teach fo 2+ years and never knew some of this about the growing pliers. Thank you so much. Am going to download your video on soldering. Again thanks. Ed

    1. Grozing pliers are definitely more difficult to master. Glad you found this helpful and I’m happy to hear you’re teaching glass too! It’s such an amazing art form and so much fun to see what others can create.

  2. WELL DONE! You have a gift for teaching others. Rick.

    1. Thanks Rick! I really try to explain things as simply as possible.

  3. I am a beginner in stained glass and this will be very helpful. Thank You

  4. Wow! I used the running pliers completely wrong on my first two projects. 😳 So happy to have found this post! The videos were extremely helpful. Thank you SO much!

    1. Same! But, I've done 5 projects before seeing this video! I think my weekend projects just got a lot easier.

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