Riku Färm
This week, we are dealing with the following question:
Why does glass come out of a tempering furnace with very small dents on it, as if small pieces of glass had been embedded into it?
For this week’s question, see our full video response below!
Usually the reason for embedded glass dents on tempered glass surface is that there’s some kind of residue in the furnace itself. When the hot glass is moving on the furnace rollers and the glass is becoming soft, residue is attaching to the glass surface. And that is what is visible after tempering, the dents from the residue. There can actually be quite a few reasons why this is happening.
The most common issue is that the loading table or the rollers are not clean enough. So when the glass is moving from the loading table into the furnace, it means some kind of residue is going into the furnace with the glass, which is causing the issue. So, the first thing to check is the condition of the loading table rollers. Clean them frequently. Also, if your furnace rollers are already dirty, make sure to clean them before starting production again. The second thing to check is whether your glasses are clean enough after coming from pre-processing. Residue from pre-processing causes the same issue, so always make sure you have clean glasses before tempering.
As always, remember to learn, share and succeed!
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Glastory 
Hi I’m tempering operator and wanted to know how to get a temperature down when it are overheating while running 3/8 and 1/2? My operator ran some oversized test glass through it to get the temperature down but it melt on the rolls that damage 19. I believe he soak it in too long in the furnace and turned off most of the top and bottom elements switch off.