SO2 – Sulfur Dioxide – is it worth the headache? Short answer = YES, in very small doses. That being said, Separating the myths and truths about SO 2 is always a good place to start. A popular misconception is SO 2 is used to coat the ceramic rollers in the heat chamber. In fact the opposite is true. The object is to very, very minimally coat glass NOT CERAMIC ROLLERS. Tell tale signs of too much SO 2 is blue coloration on glass when it exits the tempering process. All this will accomplish is excess gas coating the ceramic rollers which results in a spotty build-up of a brownish material. Sooner rather than later this build up will break away depositing itself on the glass with a good chance of taking piece of ceramic roller with it, which , in turn, causes further damage to downstream product.

How much should I use and when? I have found through much trial and error that, obviously, less is more. For best results a 10 to 30 second bust only after the tempering furnace has been sitting inactive for 3 or 4 hours. Prior to the first production run of the day is the best time. You will have to play with the volume of SO 2 to find the correct amount of that works for a respective Tempering Furnace as all vary in size and SO 2 delivery. One time a day usually was enough for me but occasionally 2X depending on production volume and glass type/thickness. Run a hand over finished product before storing, it should be smooth. If slight “bumps” or “Sticky” patches are felt, it may be time to add a little. Again, it is trial and error to find the sweet spot. Err on the less SO 2 side of usage.

BUT SO 2 EATS THROUGH METAL…. Wrong again. SO 2 in its dry gas form has minimal if any effect on steel or stainless steal. The issue only rears its ugly head when water is introduced to the mix. This is more prevelant in the wet and/or humid parts of the country where high humidity levels saturate the air with water and mixes with SO 2 in the Heating Chamber. This mixing can introduce miniscule amounts of Sulfuric Acid – SO 2 + H2O = H2SO4 – which can have a damaging effect if found in lage enough quantities. It is Acid after all. That being said, using minimum quantities of SO 2 should not be an issue even in high humidity. It is overuse of this tool that causes problems, not he tool itself.

Ok, we now we have nice flatclean evenly heated glass exiting the heating chamber. So why is glass still being damaged/ breaking. Assuming all cleaning and maintenance is kept up regarding the cooling section, especially, I would say time to fine tune glass exit temperatures. A simple but effective way to guage the correct temperature range without any major investment is to watch glass entering the cooler from the heating chamber and mark where it loses its “red” or “regains” its color. Two ways of saying the same thing. Point being there is a definate point where the color changes and by knowing where it is we can guage how hot (or not) the glass is. If the color returns much before this point chances are it is going to break….. after, and we risk burn marks. Using a simple infra red temperature sensor as the glass exits the heating process will give a better idea of where you should be for best quality and production. This can be done very cheaply, $25 in the hardware store and some paper all the way up to movable sensors with a display monitor at the control station. It all works out the same in the end.

And that’s it for Tempered Glass Tips. Hope I was able to shed a light on a few easy fixes. As always, drop me a note if more info is needed. I will do my best to share any knowlege I may have acquired on my Glass Merry-go-Round.

Before I run, gotta give kudos to Jorma Vitkala, Chairman GPD. and his Glaston/Tamglass Technicians for having the patience to listen to all my neverending questions through 2 Tempering line installations, 1 complete rebuild, many service calls and many, many cries for help in the middle of the night. You created a monster and I am very much in your debt.