Cetie also gives guidance for metal caps!

Glass bottles are generally closed either by a system that creates a seal inside the bottleneck, such as corks or their substitutes, by a cap that creates a seal on the upper edge of the neck (the lip), or by using mixed sealing areas: the lip plus part of the interior, or even the lip plus part of the exterior.
Closure systems have many functions other than just sealing: the ability to open and reseal a bottle several times, resistance to internal pressure, demonstrating the integrity of the closure - the tamper-evident feature, anti-refill, anti-drip or dosage, and of course the aesthetic functions and communication associated with the brand. Some of these functions are defined by surprisingly demanding specifications: In the wine domain for example, the same closure is often expected to prevent the liquid from getting out while the bottle is horizontal, but at the same time allow air to pass into the bottle, and what’s more, to a very precise degree. 
The closure system necessarily involves at least two elements, working closely together:

The whole system is generally defined by the cap manufacturer:

They design the finish and the cap and define the dimensional tolerances of the finish so that the caps fit. For the major existing systems (beer bottles, wine and spirits bottles, etc.), the finishes are strictly defined by standards that are discussed at length at Cetie, regularly updated, and published either by Cetie or through European standards (EN standards). Based on these finish standards applied by all glass manufacturers, each cap manufacturer defines a solution tailored to the specific requirements of each customer, and which also fulfils the numerous functions required.
All of this seems to advocate a very limited collection of glass finishes (with few models) and infinitely diverse caps - why not one solution per cap manufacturer, customer and type of bottle? On top of that, there is the bottler to consider. The latter buys the bottle and the caps and then has to assemble them on a relatively standardised production line. And above all, it is important to take into account a feature that is not widely known: caps are most often delivered in an intermediary state, not in their final form. So, it is the finish of the bottle that will act as a template for the shaping of its own cap. Thus, the beer “crown” cap is crimped around the attachment point of the finish. The cap of a spirits bottle is a simply closed cylinder, which is pressed against the threading of the finish such that it fits perfectly, so it is the glass finish that models the cap threading. The capping step combines shaping and assembly in the same operation.
The complexity of this is sometimes underestimated by the bottlers themselves, even though this key step requires significant technical expertise and attention to detail. This is why industry stakeholders put together Cetie guide n°11 “Metallic screw capping defects: identification and correction”. This 45-page document, published at the start of the year, comprises 34 datasheets, each one illustrating a defect with a visual aid, and specifying the potential causes and consequences of the defect. Part of the guide is dedicated to the resolution of problems encountered on the line and specifies the corrective actions or checks to be carried out in order to resolve each problem. As for all Cetie guides, it combines expert skills from the various professions involved: bottlers, machine manufacturers, cap and liner suppliers, and glass manufacturers.
This guide usefully complements Cetie guides n°2, n°6 and n°9, each of which is dedicated to the application of one type of cap and is also based on the cap specification sheets and the standards defining the finishes. It accompanies and supports any technician dealing with the aluminium capping of bottles, be it a BVP, BVS or even an MCA finish, to help them to perfectly master the Caps-Bottles-Machine trio.
 

 Cetie metallic capping guides:

• Guide n°2 - Metallic screw capping for non-carbonated liquids, foodstuffs and pharmaceutical products on BVP type glass finishes
• Guide n°6 - Metallic screw capping for still wines on BVS type glass finishes - with redraw
• Guide n°9 - Metallic screw capping of pressurised wines & other beverages on BVS type glass finishes - with redraw
• Guide n°11 - Metallic screw capping defects: identification and correction
• Guide n°4 - 26 mm crown capping
• Guide n°12 - Recommendation for flaconnage crimping

 

Finish standards and technical data sheets:

• EN 15543 – Screw thread finishes for ... non-carbonated liquids (BVP finish)
• EN 16293 - Deep BVS finishes for still wines
• Series EN 16287 to 16291 – MCA Finishes
• ISO 12821 and ISO 12822 – Crown finishes
• Cetie GME 14.01 and GME 14.02 – Twist crown finish

 

Cap standards and technical data sheets

• Cetie EC4.01 - Aluminium screw caps for still wine on BVS glass finishes
• Cetie EC4.02 - Aluminium screw caps for pressurised liquids on BVS glass finishes
• Cetie EC4.03 - Aluminium screw caps for still liquids on BVP glass finishes
• EN 17177 – Crown cap
• Cetie Guidelines N°17 - Specifications for aluminium screw caps for wines and alcoholic beverages