A comprehensive introduction to beer caps (crown caps). It is not only a key component of beer packaging, but also a profound industrial design masterpiece.
1、 Overview: A standard for defining an industry
Crown cap, also known as crown cap, is a standard metal bottle cap named after its 21 serrated coronal folds on the edges. Since its invention in 1892, it has almost dominated the packaging market for beer and soda glass bottles, becoming one of the most classic and well-known packaging components in the world.
Its core mission is to achieve absolute airtight sealing while withstanding the internal carbon dioxide pressure to ensure the freshness, flavor and foam quality of beer.
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2、 Core Structure and Function Analysis
A standard crown cover mainly consists of three parts:
1. Cover shell
Material: Tin plated steel plate (tinplate) or chrome plated steel plate. Provide structural strength and rigidity.
Feature: There are 21 standard folds on the edge. This number is an optimized result that provides the best opening and closing convenience and production stability while ensuring sealing. The inner side of the cover shell is usually coated with a very thin protective coating to prevent the reaction between the alcohol and the metal.
2. Sealing gasket (inner gasket)
This is the core technology that directly determines the sealing performance and food safety. The specific material evolution is as follows:
Traditional PVC gaskets: containing foamed PVC layer, with good sealing performance but environmental protection and potential migration risks, are being phased out.
Modern PE/PET gaskets: currently mainstream, using food grade polyethylene/polyester materials, safe, non-toxic, and environmentally friendly.
High end coated gasket: Apply a layer of elastic food grade coating (such as epoxy based) directly on the inside of the cover shell. After opening, the bottle mouth is clean without any gasket residue, which can maintain the original flavor of the beer to the greatest extent possible, making it the preferred choice for craft beer.
3. Oxygen absorption layer (optional but increasingly important)
Many modern crown covers, especially those used for high-quality beer, integrate a layer of oxygen absorbing material into the gasket. It can actively absorb residual oxygen in the top gap space after sealing the bottle cap, as well as trace amounts of oxygen that may infiltrate later, greatly delaying the process of beer oxidation (producing cardboard flavor) and extending the flavor preservation period.
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