Hi, I am Phillip McKee of McKee Stained Glass. Right now, I am going to show you how to cut and break an inside curve. An inside curve is when you are cutting a curve and keeping the glass here and throwing away the glass inside the curve. This is the most difficult cut in stained glass. When you are cutting an inside curve, let us say that this is the piece we are trying to cut. Notice the piece of glass I am using is bigger than the pattern piece. When you are cutting out this piece, you will cut out the inside curve first. Always make sure there is safety margin on either side. If this curve had extended all the way out to the edges of our glass, then we are very likely to break off and lose these two horns. But since we have created a safety margin, any loss will occur in the scrap glass, the glass we are throwing away.

It is always important to plan out your inside curves, for that I often use a sharpie or other marker. First, draw on your inside curve, then plan a series of curves that are parallel to it. I like to use at least two extra scores, if possible three, so I draw on my extra scores, each one slightly flatter than the one before it. Now, I know where else I am going to score. To break inside curve using this method, you will begin your scores. First on the actual curve you are going to keep, second you score the one next to it and finally, you score the one farthest away. Only after scoring all three, do you begin breaking your glass. You start with the farthest out and move in until finally you get back to the score you want. Why do we do this?

Because every time, you score or break glass, you are creating micro fractures wherever there is a weakness, you may not be able to see them, but if you build upon these micro fractures, along your score lines, you make them easier to break. When we do our first score, we are breaking the surface tension, with our second score we are creating micro fractures in the first. With our third score, we are creating micro fractures in the second and additional one in the first. So, as we break beginning from the outside and moving in, with each successive break we are adding more and more micro fractures to the existing scores. So, finally when it comes time to break, the score we wish to keep, we will have a very easy time of it. So, let us begin. Put away our marker, put on our safety goggles and get our cutter.

We begin with our first score and it is better to rotate the glass than to try and torque your body when you are doing your score. Now, we do our second piece and finally, our last and flattest score. Now, it is time to break this, a good idea whenever you are breaking on the inside curve is to tap out along the score. This helps create additional micro fractures and makes your job easier. Start off using an old style cutter, these steel wheel cutters can be found very inexpensively at a variety or locations. It is not a good idea to use them because they have no inside oil reservoir and you have to apply cutting oil to the wheel each time you score. They also do not come with a higher quality cutting wheel as you will find in most other cutting appliances.

But, they do have a ball end on them and we can use this ball into our advantage. Hold your piece of glass with your thumb and ring finger on one side of the score and your middle finger and forefinger on the other. This provides a nice, strong grip on either side of the score. We do this so that we do not waste energy popping the glass up and down and instead apply all our energy to the tapping. Tap from underneath and aim to hit directly on the score. Do not be scared to use thumb power when doing this. Simply tap up, as you tap, you will hear that distinctive note, this note will change as the fracture progresses. Then if you are lucky the glass will break directly along the score. Move to the next score, tap it up; if you do not want to continue tapping, all the way until it breaks, you can move over to your Breaker/Grozer, score it, grab it in the middle after having tapped and wiggle up and down along the score at various points.

Finally, it will break off. Now we move to our last piece, our last score. After you have tapped, you can move on using your Breaker/Grozer, wiggle it up and down and it once again comes off. Only after you have removed the inside curve, can you move on to the other pieces. Next, we are going to learn how to cut an entire shape out of glass.