How Glass Bottles Are Made

Submitted by: buttersrules 1 week ago in Tech
 
In a recent exchange with sqrlz4ever about the appallingly hot weather here in South Australia, I mentioned a few things about my work as a glassmaker, and the temperatures that I deal with on a daily basis. I shared this video with him, and he suggested it would make an interesting post, with notes from an insider’s perspective. 
 
So, How it’s made – glass. 
 
As a glassmaker, my job is to operate and maintain forming machinery similar to what is in this video. My suggestion would be too watch the video first, and then, if interested, go through my further notes (which seem long, but this is the condensed version….it’s a complicated process, lol)
 
I could make this just the first post in a series; it’s a subject that I find fascinating. But such detailed breakdowns are pretty time consuming, so if you want more, say so! If there’s enough interest, I’ll continue. Cheers.
 
Notes:
 
55 seconds: cullet not only comes from purchased recycled glass, but also from any glass that has been manufactured and rejected, weather it's rejected at the forming machine, by the inspection machinery, or has been quarantined during quality inspection.
 
1 min 9 seconds: 2730 f = 1500 c.
 
1 min 17 seconds: The glass actually passes from the furnace to the fore hearth, and then flows into what is referred to as the sleeve. The sleeve is essentially a drum, I'm not sure if the actual capacity, but approximately at a guess, 100 L. Beneath that is an orifice ring with a number of holes in it corresponding the amount of gobs required for each section. Normally it is two or three. My machine runs three gobs per section. 
 
1 min 45 seconds: The preliminary mould is also referred to as the blank mould. Commonly, it's just referred to as the blank. The glass is formed into the parison, either by compressed air, in the process known as blow and blow, or by a plunger pushing up from the underside, which displaces the glass, forcing it into the blank cavity, in a process known as press and blow.
 
2 min 17 seconds: As the formed bottle exits the mould, it is cool enough to be able to maintain its own shape, and yet so hot that it is still in a state of plasticity. If, at this point, you removed a bottle from the conveyor, and dropped it to the ground, it will bounce. I haven't taken specific temperature readings, however the temperature somewhere in the region of 500-600 degrees Celsius.
 
2 minutes 56 seconds. The type of mould shown at this point can be particularly problematic. When the mould opens the glass needs to smoothly release from the surface of the mould, and as such, the mould itself needs to be lubricated at points of highest resistance. Engraved or embossed logos, such as in this example mould, require special to ensure that the glass releases from the surface cleanly.
 
3 minutes 37 seconds. In the annealing lehr, the glass is actually reheated initially, and then cooled at a controlled rate. If you consider the sidewall off the glass, the external surface will cool at a quicker rate than the internal surface, and as such, it will attempt to warp. Obviously, due to its nature, soda glass is unable to do so without breaking. The purpose of the annealing lehr is to enable cooling of both the inside and outside surfaces evenly. This Is why glass that has not been correctly annealed, or tempered, is not only prone to breakages, but the release of the internal stresses can be quite violent. It won’t just crack, it will shatter, and the release of the energies involved is so sudden and violent, it is more akin to an explosion.
 
3 min 54 seconds onwards: The packaging line shown in this video appears to be much more automated then the processes we use. Whilst we have similar automatic inspection machines, the need for quality in the finished product is such that human intervention and action cannot be fully removed. The machines need constant monitoring to ensure that the inspection process is doing what it is intended to do, and there are many flaws and quality aspects that cannot be picked up by these sorts of machines on a practical basis.
 
Manual gauging buy a cold and operator is done to ensure the integrity and accuracy of the automatic inspection units, and further, more detailed, digital sampling is done a few times per shift 
 
4 minutes and 50 seconds. Not only does an increase culler ratio reduce manufacturing costs, if the cullet is of high quality, the glass produced in the furnace is much more stable and consistent, which allows the forming machines to produce ware of a higher and more consistent quality. One of the main issues we face is obtaining cullet of sufficient quality in the quantity that we would desire.
There are 22 comments:
Male 748
Do you have the same rules about having water bottles, lighters, etc on the production floor as aluminum molding companies? (which is to say, none allowed)
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Male 1,077
seems like there's a good interest in this sort of post, I'll continue...got several more interesting ones, will try and post in the next few days...
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Male 418
buttersrules Post away.  Rather read, watch, and learn something new than see constant Trump, social justice shitposts.
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Male 418
Damn, informative post.  Nice job.
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Male 362
THCW - Too hot, couldn't watch.
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Male 6,171
sqrlz was right. I found that quite interesting. Thank you.
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Male 4,750
MOAR manufacturing pron!

I always love these videos.

You mentioned issues with getting high quality cullet, is it a price or availability problem?

What are people mixing with cullet that lowers the quality?
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Male 1,077
daegog price isn't the issue, really. It's that a lot doesn't meet our quality standards. partly poor sorting at recycling depots, partly the metal sleeves over the necks of wine bottles, or screw caps being left on. These melt in the batch, and cause metalic stones in the finished product. Through our own processing, a lot of this metal is removed prior to the glass getting anywhere near the forming machine, but when there's a shitload of it, it makes it so much harder.
Also, people putting shit in empty bottles that they then recycle. Some burns away, but other things don't. It's all impurities, and we can handle that to a good degree, but too much is just too much. 
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Male 6,053
buttersrules Interesting. I guess I really should be giving those bottles a quick rinse before tossing them in the recycling bin then. I would've never thought about the metal on wine and champagne bottles. Now I know.
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Male 6,053
Thanks, Butters. It's always interesting when an IAB'er gives a look into a subject he knows on a professional basis.

This video and your comments gave me new appreciation for just how sophisticated the everyday glass bottle is; the chemistry and engineering behind it all have taken hundreds, if not thousands, of years to develop.

Lastly, for those who might've missed your comments originally, can you recount here about the temperatures you deal with at work and how they affect your clothing?
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Male 1,077
squrlz4ever well, i mentioned that the glass up near the shears is just over 1100c...sometimes need to go up there, and can be standing about 3 feet away from a stream of it. Pretty toasty.
also need to change out the blanks and the moulds periodically, either as routine preventative maintenance, or in the event of damage. The replacem are preheated in an oven at 400c, and when we change them out, we need to run the section for several minutes for them to heat up to operating temp.
As mentioned, the bottles come out at around 500c...so when changing a mould, the individual section will be stopped, but the rest of the machine is running....you have a good chunk of your body jammed into this small space that has recently had 600C+ glass in it, and just inches away, on either side, a still running section....and your on a platform over the conveyor, so red hot bottles are running past directly beneath you, between your legs. Even with the heat shielding the platform gives you, pretty warm.
If your gloves get wet (water, sweat, or oil), you need to change them out, or you'll get steam burns.
Standing directly in front of the machine for a few minutes, your clothes will get to about 100c, and you need to step back under the aircon vent for your clothes to cool, or you could get burnt. You can start to smolder, as well, if you  stay there too long.
And mobile phone in your pocket? No way. Too dangerous, the battery can explode.
The effects of heat on the body is a major safety concern, and they're really vigilant about the safety aspects. Electrolyte drinks in multiple flavours, ice machines, airconditioned booths, recovery time if needed, etc.
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Male 6,053
buttersrules Thanks. I find those details pretty fascinating, for some reason. Steam burns from your sweat!  O.O
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Male 3,842
squrlz4ever I don't know about clothing, but that temperature could probably melt steel beams.
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Male 9,002
Thanks buttersrules. Glass is a simple, yet fascinating, substance. 

Informative and entertaining. 
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Male 748
Where in the process does the cavity get formed and how?

When globs are running through the slide do they require lubrication?
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Male 1,077
muert 2nd q first...yes, lubrication is required. When the gob is first cut, it goes into the scoop. this is mounted on a distributer, that rotates it. from there it fires into the trough. Troughs are oiled occasionally. After the trough, it hits the deflector (scoops, troughs and deflectors are all basically the same thing, just different lengths, angles, and position. The deflector changes the direction to a downward motion, loading the glass gob into the blank). The deflectors are lubricated with a light oil via compressed air spray gun by the operator on a regular basis. The frequency depends on the specific bottle being produced....usually, though, 15, 20 or 30 min intervals.

re first question...not entirely sure what you're asking. The cavity is the hollowed section of the mould. The blank mould has a cavity that is smaller than the finished product, which forms the parison, which is essentially the preliminary shape. The glass is pressed into the cavity either from a small plunger forming a small hole, and then air being blown in, causing the glass to fill the blank cavity, or from a larger plunger forcing a hole, and the displacement of the glass from the volume of the plunger forces it to fill the cavity. (these holes, btw, are the hole in the kneck of the final bottle....so essentially, on the blank side, the 'bottle' is upside down). After the parison inverts over to the mould side, the hole is now on the top, the mould closes around it, and a blowhead comes down forcing compressed air in, blowing the glass into the cavity of the mould, making the final shape.
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Male 748
buttersrules Different terminology I think. I was referring to the empty volume being created in the slug which air is blown into, as opposed to the empty volume in the mold which shapes the exterior of the glass.
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Male 4,655
buttersrules I was hoping for a more smartass answer to "When globs are running through the slide do they require lubrication?". Your're slippin' butters.
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Male 3,820
you ever make any bongs?
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Male 1,077
robthelurker no, never. Back in the day, I've been told, some guys used to cut down the hot odd hot bottle to make ash trays. Couldn't do that now, though, they'd have your guts for garters.
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