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Fire1981

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Those are marks from a bad shear cut. Cold roll marks happen. But there are roll marks from many more problems than cold rolls. About the only time you get cold roll marks is at the start up after a machine has set idle for hours, days or weeks. The only way the rolls get heat is from the hot glass rolling across the rolls. Depending on the size of the rolls, it can take fifteen minutes to a hour for the rolls to get hot.  At 200-250 per minute that is a lot of cold roll marked or out of round marbles. These are usually rejected and discarded.  There are many more hot roll marks than cold roll marks. Many things can cause roll marks. Glass temperature, speed, hot glass glob size to small or to large, glass buildup on the rolls, and more. Unless you were present at the time, how would you know a roll mark was caused by cold rolls ?  Cold roll mark has been used for many years, but it is in most cases not correct. Just roll mark would be more accurate. But like many things around marbles. once it is in print and used, it is very difficult to change it. I explain this at least six or a dozen times per year, for years. But people still label all roll marks as Cold Roll Mark.  I have heard it so much, that I have caught myself using, cold roll mark.  

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