Posted 13 October 2006 - 04:43 PM
Labeling (otherwise known as decorating) is someting I have a great deal of experience with. Before I get to beer bottles, I will go down memory lane to a job I had when i was 21 years old...
I used to operate a machine that silk-screened the labels on Flex Shampoo and Conditioner bottles. Running the length of the machine were two parallel rails with evenly spaced cutouts. One had a cutout to cradle the neck of the bottle. The other had a cutout to cradle the bottom of the bottle. The cutouts were about six inches apart. There were these articulated mechanisms that would pick up all the bottles in the machine at the same time and move them one spot to the right placing them in the next cradle. This mechanism was set at 76 bottles/minute.
There were gaps in the rails where different operations would take place in the decorating process. Right at the beginning of the process was a flamer. It was a bar with holes in. Gas was pumped into the bar and there was an ignition system. I controlled this to make sure I had a steady set of blue flames coming out of the holes. A mechanism would pick up a bottle and pass it through the flame during the transit time from one station to the next and then set it in the next station. Because the bottles I was decorating were not round this process was done twice, so that both sides of the bottle got flamed. The purpose of flaming was to "open the pores" of the bottle. This is how it was explained to me. In simplest terms, if the bottle was not flamed, the ink would not stick to the bottle.
After the flamers came the ink stations and light stations. The bottle would be picked up and lifted to the bottom of a wood framed silk screen that was clamped into the machine. Then three carefully syncronized mechanisms would ink the bottle. The bottle was rotated so that it rolled along the bottom of the silk screen. The silk screen was passed over the bottle so that there was no slide between the two surfaces, and a squeege would scrape across the top of the silk screen forcing ink through and onto the bottle. At the same time the mechanism holding the neck of the bottle would inflate it with air so it would provide even resistance to the squeege. Too much pressure and the ink would be too think and the bottle unreadable. Too little pressure and the opposite would happen. If you didn't put enough air in the bottle it would have uneve pressure and be dark at the ends and light in the middle. Too much air and the bottle would be over inflated and it would be dark in the middle (and smeared) and light at the ends. The other complication was bottle quality. The blow molders that make the bottles provide variation in quality. There are thick spots and thin spots in the bottles. These problems cause with how the bottle inflates and presses against the squeege. And a defect in the nect where the "crown" is removed exiting the blow molder can cause a bad seal with the air injector. An uninflated bottle could cause such a disrepancy in pressure that if the silk screen was too tight on the frame the squeege would rip it, dripping ink into the machine and causeing a cleanup of an hour or more.
After the ink station was the light station. The ink we used was UV dried ink. And we had these hooded lights about six steps past the ink station where the decorating you just put on would be dried. I had 20/20 vision when I got my job at Revlon. I needed glasses 9 months later when I left because of improper exposure to those UV lights. My own fault in retrospect. But that is another story.
There were three ink stations on my machine. It would ink the face once, and the back twice. Once with the lettering color, and once with black for the barcode.
If the bottle was not flamed correctly the letters would slip off and fall into the bottom of the machine. Otherwise the ink was actually adhered into the surface of the plastic, and you could not get the ink off of the bottle, you had to scrap off plastic to get it off.
At the end of the line I would take samples of the bottles and throw bad ones into a grinder that chipped them into tiny peices and put them back into the extruder to the blow molder. 100% recycling of scrap into the process again. At color changes we would put the ground material into drums and sell it to companies that make plastic things that have no color spec. I am sure you have seen these from time to time.
After the silk screening, the bottles went into the hot stamper. Here I had a machine that used a gold transfer foil to gild the raised REVLON letters on the bottle. This operation also inflated the bottle with air to keep even pressure against the heat elements. Too hot or too long and the plastic liner on the foil would melt. Too cold or too short a time and the gold would not transfer.
The other trick with these machines was aligning the silk screen so that the image was on exactly the correct spot on the bottle, and was perfectly straight. I learned so much during this job about industry, that I can not even begin to describe. This is a very high overview of how silk screen decorating still takes place today.
Many glass bottles use silk screening. But because they are a solid object the process is different. The bottles are heated, decorated, and kept in a kiln. Some may also use UV drying. After the bottles cool they go to the filling lines. You can fel the raised lettering on a silk screened beer bottle.
Another older technology is the use of paper labels glued onto the bottle. These were loose labels that had glue applied to the bottle, and then the label presed onto the glue. Then an oven was used to dry the glue and insure a proper adherance. you can recognize these because the permanent adhesive used is far stonger than the paper, so when you try and peel it off it alway leaves paper residue on the bottle. Even so, because of the paper the labels degrade in water and have a tendancy to fall off of the bottle.
Newer technology uses pressure sensitive material (peel off back adhesive films) as the label. Clear films are decorated and die cut on a traditional press. Docorating si the multi-pass, multi-color color process for making any label. Die cutting is where the lable passes under a die; a roller with shaped impressions on it that is engineered to cut through the face material, but not cut through the backing material (liner). The excess is (known as the matrix) is then peeled away leaving just the shaped labels on the liner. These labels are on large rolls, some as many as 20,000 feet long. The labels are removed from the liner and put onto the bottles at a very high speed with no cure time needed. The trick with these labels is having a glue that will not break down during the lifetime of the bottle. And it is recent innovations in thin clear films that has allowed for this type of labeling to be as visually appealing as traditional silk screening. Beer companies all over the world are in the middle of chaging technologies. And it is reducing the cost of supplying beer in the process.
Take a longer look at the outside of the next bottle of beer you drink. There is a huge industry out there that works day and night to make that bottle look as good as it does. I find it fasicnating how much engineering goes into the simplest of things.