The Irritation of the Glass Jar Screw Cap

How many of us are fighting to open the screw cap of a glass jar. Am I the only one with rheumatic fingers and no power anymore in my hands? No, I am not. It is a general complaint of consumers in regard to glass jars. And the processed food industry or the glass industry for their part? Well, they think they can get away with it, by letting their costumers buy a Black&Decker or any other fancy jar opener or use some ridiculous manual tool to punch a hole in the cap.

Haven’t there been any developments for easier screw caps for jars? There have been. When you search the international patents database you find various, some simple, some complicated. But no one ever reached the market commercially. Yes, I know an easy-open screw cap is probably more expensive and that seems to be the bottle-neck. However some see signs that the glass jar for processed food may be experiencing a large decline in market share from the growth in use of PET-jars, paperboard cartons and flexible stand-up pouches.

Furthermore it goes without discussion that consumers are still focused on convenience and that by showing just a little bit more creativity and innovation, an additional small feature to a product might actually attract much more consumers to buy the product.
We should learn, at times, to focus on the finer details of product presentation.

One of these small additions is the “Abre-Fácil“(Portuguese for easy-open) screw cap for glass jars. Metalgráfica Rojek Ltda, a Brazilian company specialized in the production of metal packages for food products, is the original inventor of the “Abre-Fácil” screw cap.
We all know that the reason a screw cap of a glass jar is only to open using force, is due to vacuum inside the jar. The products are hot filled and after cooling the free space in the top of the jar has drawn a vacuum keeping the screw cap closely fixed to the glass rim of the jar and in this way securing the shelf-life and integrity of the product. That’s why we punch a hole in the cap to eliminate the vacuum, so that the cap can be screwed off.

This principle (eliminating the vacuum condition) Rojek used for its “Abre-Fácil” caps.

The screw cap, made from steel, has a small round protection seal, made from polypropylene, in the centre of the lid. By lifting this PP-dot, air is allowed to enter the container, which facilitates the rotation of the screw cap. As it is a screw cap, the jar can be re-closed and re-sealed after opening, allowing gradual consumption.

Yes, it is that simple, although to manufacture the screw caps is a bit more complicated. To make the special lid, a metal disc is formed into a screw cap and a hole is punched into the centre before a dot of polypropylene is applied to the hole on one side. The lid is then flipped over, and a very small dot of polypropylene is applied to the underside, which bonds both ‘dots’ together, creating something like a double flanged seal.
The one covering the hole on the outside must adhere reliably yet still be peelable when the consumer needs to break the internal vacuum and open the jar. As for the polypropylene over the hole on the inside (bottom side) of the cap, it has to bond to the polypropylene on the opposite side of the hole so that when the consumer peels the outside PP-dot off, the inside compound will come away to release the internal vacuum.

The seal can’t be removed completely: even after lifting, a small part of the PP-dot remains glued to the cap. This allows the air-inlet to be covered again after the loss of vacuum, increasing the protection of foods that are not consumed.

Is this a new packaging invention? No, not really. You will be shocked to know that the “Abre-Fácil” technology has been present in the Brazilian market since 1989. I present it here today, as Rojek has perfected the “Abre-Fácil” for glass jars and re-introduced it for the range of palmitos of Gini, baptizing the screw cap “BR-1”.
To complete the story Rojek also manufactures cans with an “Abre-Fácil” lid. Very popular in Brazil, among others with various products of Nestlé, many tomato sauces and chocolate creams.

And (as far as I know) only once used in the USA (in Europe I never saw them) with a steel food can by Hirzel Canning Co. for its Dei Fratelli Pizza Sauce and Italian Dip. An easy-to-open, reclosable, 12-oz steel can that used, what Silgan Containers called, Dot-Top technology. Silgan licensed the technology from Metalgrafica Rojek Ltda, the original Brazilian inventor as described above.

The construction of the can lid or can end is similar to the screw cap of the glass jar. The lid of the can has a central vent hole sealed using a plastic plug. Once the seal is broken, the internal vacuum formed during the sterilization process is released by removing the plug and the end can be taken off. An additional benefit is that the end has a unique re-closable feature. Imagine a re-closable can. No can opener needed.


13 responses to “The Irritation of the Glass Jar Screw Cap

  1. interesting, but how do ypu protect the product from people who think they are fnny by opening the seal in the shops?
    Is there any possibility to show that the seal has been openend ?

    • Due to vacuum the screw cap is concave as long as the vacuum isn’t broken. Unfortunately we have to secure out packages. A tamper-evident seal is required. Can be a seal over the top of the cap or a shrink wrap seal over the top.
      Don’t tell me that nobody is using an extra seal for the standard screw cap. That’s right, that’s why nobody knows whether a screw cap has been opened in the shops and the vacuum released. In principle every packaging should have a tamper-evident seal or closure.

  2. Funny subject sinced it was resolved way back in the 1800’s. Yes, tha’s right. Remember the old filp clamp Mason jars?

    The problem now is the requirement of tamper evidence and the lack of reusing such an expensive jar.

    Sorry to ingest here…..just reminded me of a conversation I was having with a group just the other day.

    The subject was an interesting one. Sustainable packaging vs. Simplified packaging and where will we be in 15 years.


    • Although Mason jars have the feature to open more easily than the standard screw cap, it’s not (and never have been sold as) a easy-to-open glass jar. And ‘reusing such an expensive jar.’ Glass is one of the best recycled packaging formats in the world. It’s one of the few true examples of ‘Cradle-to-Cradle’.

  3. It was intersting to read this topic, once I am Brasilian and very well familiar with this easy open system for years. If you look at the “Gini” cap again, you will notice that aside the tamper evident, the cap can once again close the jar and so reuse. Other applications of this caps are in cans, which will not be resused and in jars that the cap cannot be reused, but those jars I mention, look more like glasses and is widely reused as glass by majority of people from class C and D. However, most of those glasses has been replaced by plastic nowadays.
    One more comment, if the tamper evident is been removed, you will notice the cap loosen. I do make a lot of field study at supermarkets, and I have never found this caps violeted at the shelves.

    • Mirelle,
      First of all: The Abre-Fácil is NOT a tamper-evident closure. That’s one of the weak points of the system. Fortunately, and contrary to the ‘civilised world’ (USA and Europe) tampering a packaging is not a big problem in Brazil. Not criminalized anyway. But it happens. If you do ‘a lot of field study’ don’t go solely to the biggies, like WalMart and Pão, go to the mercadinhos and small supermercados in the bairros. You will find them. Accidentally opened or by stupidity (lack of education) they are there. But again, fortunately not criminalized, as in wilfully poisoning brands and blackmailing, as we see in other markets. In general packaging in Brazil is so much easier and simple.

      To the smaller glass jars for polpa de tomate, as example, the closure is not a screw cap, and I left them out, as you always need a tool to open (even if it’s a simple coin).
      I agree with you that the Abre-Fácil is very popular in Brazil, and wrote the article, wondering why not in the rest of world,.

  4. Very interesting article. Some people with arthritis will still have trouble opening this type of lid if the force required to pull the dot is too high, if the size of the dot is too small, or if the dot is difficult to grasp because of low friction.

    You might be interested in taking a look at our site ( that deals with ease of use in packaging. We do a lot of research in packaging ease of use as it pertains to older adults and adults with arthritis. Most of our research is documented on the site. We also have a ease of use monograph on bottles and containers that attempts to address some of the concerns you mentioned.


    • Brad, thanks for your comment.
      In the first place the dot is easy to remove. Particularly when using a knife or something similar which scrapes along the surface of the cap. A movement without any force.
      I have arthritis in my hands (sometimes can’t even bring a cup of coffee to my lips) but have no problem removing the dot.

      To your website. I will visit it and see whether I can use some items for a further article, as I think packaging designers and technologists need to be aware more of the problems of consumer minorities. See also my articles about Braille integrated in packaging.

  5. The easy way to see if someone has already openned the can is simply trying to open it yourself – it’s nearly impossible if the vacuum still hold on, trust me. And it’s really really rare the case to have an already open pot in hands – have never happened to me.

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  8. Anton:

    I have a customer who is interested in this technology. Is there a North American manufacturer of this type of product? Failing that, does this Brazilian company have a North American manufacturing arm?


    • Grant, as far as I know one of the subs of Silgan Holdings has been rep for the Brazilians. I have to say that several changes and merges have taken place after I wrote this article. I am not sure whether Silgan still is supplying this cap. Try there, if not successful come back to me and I will see what I can do.

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