Q&A for How to Cut Tempered Glass

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  • Question
    How do I make stained glass?
    Douglass Brown
    Glassblowing Expert
    Douglass Brown is a Glassblowing Expert based in Half Moon Bay, California. He has over 25 years of experience as a glass artist, and is the owner and operator of 2 glass blowing studios in the San Francisco Bay Area, Half Moon Bay Art Glass and Mare Island Art Glass. Douglass believes in sharing hot glass experiences with anyone who wants to learn about the processes of blowing and sculpting glass. When not teaching, Douglass creates glass art that is a mix of his takes on nature and functional glassware. He has also created the Glass Troubadours, which is a mobile glass blowing studio that hosts parties, events, and visits craft shows.
    Glassblowing Expert
    Expert Answer
    Creating stained glass has evolved over time, and while the traditional methods required intricate craftsmanship, modern techniques make the process more accessible. In the past, artisans would collect molten colored glass from a furnace, forming a bubble that was manipulated into intricate designs. This involved scoring, breaking, and unfolding the glass. Alternatively, they would spin out a bubble, resulting in "bullseye glass" with distinctive concentric circles. The contemporary approach, however, simplifies the process for easier production. Nowadays, stained glass is often made using continuous methods similar to window glass manufacturing. Molten glass is poured onto a surface from a smelting furnace, pulled, cut, and trimmed by a tractor-fed system. This results in a continuous sheet of stained glass progressing along a conveyor belt. Even glass mimicking the appearance of traditional stained or etched glass follows these streamlined, efficient techniques. This modernization has made stained glass creations more accessible to a broader audience.
  • Question
    Can I cut hardened glass with a diamond tip grinding disc?
    Community Answer
    Not without annealing it. A cut on the surface of the hardened glass will cause it to shatter.
  • Question
    When tempering annealed glass, does the glass stay the size cut, or does it expand?
    Community Answer
    It stays the same size.
  • Question
    How can I tell if glass is tempered?
    ConnorFisher
    Community Answer
    Professionally manufactured tempered glass is sandblasted with either the word "tempered" or the abbreviation "temp." Look in the corners for this mark. Tempered glass also usually has extremely smooth edges.
  • Question
    Do I have to anneal tempered glass to cut it with a laser?
    Community Answer
    Yes. The laser will cause stress points which will cause the glass to shatter if you don't.
  • Question
    Why wouldn't the glass installer drill a hole in my annealed glass?
    Community Answer
    It would have exploded into tiny fragments, and there would be no glass left. A hole has the same effect as trying to cut. You are altering the molecular structure and disturbing the combined strength of the glass causing it to shatter into small pieces.
  • Question
    What is the steady, warm to hot temperature for cutting tempered glass?
    Community Answer
    Tempered glass cannot be cut without shattering. It is designed to shatter if tweaked in order to keep people from cutting themselves. Tempered glass has to be re-heated in a kiln to 1000+ degrees F (or temperature specific to that glass type), then cooled slowly to room temperature. The resulting glass can be cut with a glass cutter without shattering.
  • Question
    How can I cut regular glass?
    Community Answer
    You can get a cheap glass cutter tool at a home improvement store, then make a mark on the glass and pull the glass cutter tool along the line, holding firmly and with moderate strength, pushing down on the glass, while pulling the tool. Make sure the glass is on a firm, even, surface, with a towel between that and the counter. It helps to put some oil along the line of cutting, to help prevent breaking the glass. Do one side at a time, and after you score it with the tool, carefully bend each side of the cut, to break it on the line.
  • Question
    Can a tempered glass edge on a door window be smoothed or polished with a pumice stone?
    ConnorFisher
    Community Answer
    Probably not; tempered glass will likely prove too strong to be polished by pumice. But, you can polish tempered glass edges with silicon carbide sandpaper attached to a buffer machine.
  • Question
    Does the glass lose its temper forever after it has been completely cut?
    Community Answer
    Yes, because it would be in a million pieces. Tempered glass cannot be cut. It must be annealed first.
  • Question
    Is glass that is tinted tempered?
    Community Answer
    A tint is a film applied to the surface of the glass. Nothing to do with the glass itself. So it may or may not be tempered.
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