Cap & Neck Finishes
A container’s neck finish holds the cap, stopper, or closure with protruding threads. A container and its corresponding cap must have matching finishes. For example, a 24/400 bottle will only accept a 24/400 closure.
Selecting the right bottle or closure is critical in selecting the right package for your application. The finish is also considered ‘the lip of the bottle’. The land area is the lip portion of the finish that makes direct contact with the inside of the cap or closure, sealing gasket or liner to form a seal. The thread is the ‘twist’ of glass or plastic onto which a CT, or continuous thread, closure is turned. And the transfer bead is the pronounced ring of plastic or glass beneath the neck area, at the foot of the finish, that is used during the molding process or can be modified to provide tamper evidence for your package.
The neck is where the bottle shoulder transitions into our finish area… The neck base is the lowest point of the neck. The shoulder area transitions between the base of the neck and the body, which is generally the widest portion of the bottle.
The neck of the bottle has various dimensions. The T, E and I dimensions are just for the opening.
- “T” Dimension: The outside diameter of the thread. The tolerance range of the “T” dimension will determine the mate between bottle and closure.
- “E” Dimension: The outside diameter of the neck. The difference between the “E” and “T” dimensions divided by two determines the thread depth.
- “I” Dimension: The inner diameter of the bottle neck. Specifications require a minimum “I” to allow sufficient clearance for filling tubes. Linerless closures, with a plug or land seal, and dispensing plugs and fitments require a controlled “I” dimension for a proper fit.
- “S” Dimension: Measured from the top of the finish to the top edge of the first thread. The “S” dimension is the key factor that determines the orientation of the closure to the bottle and the amount of thread engagement between the bottle and cap.
- “H” Dimension: The height of the neck finish. Measured from the top of the neck to the point where the diameter “T”, extended down, intersects the shoulder.
Common GPI / SPI Neck Finishes
If the thread passes itself only once, this neck finish is a 400 (for glass a 405). If it passes itself 1 and 1/2 times, it’s a 410 finish. A tall neck with two turns is a 415. A short neck with two turn is a 425. Wide threads are a 430, and finally a lug finish is a 2000.
How to Measure a Neck Finish
To find a cap’s diameter, measure from one side of the inner wall to the opposite side. Calculate a bottle’s neck finish by measuring the diameter of the outermost threads. The resulting millimeter measurement will be the “T” dimension. Then, see how many times the threads pass one another to determine the finish.(ex. 24 mm “T” dimension with 1.5 thread turns = 24/410 neck finish)
The label area is the area of the bottle’s body where a label or print decoration can be applied.
The bottle bottom comprises the foundation of the bottle. The heel is the point on the bottle where the body begins to curve into the base. The base is the very bottom of the bottle – which includes the push-up, the concave area that helps to ensure stability, reduces the interior volume of the bottle, and allows the base to be marked with a recycling code, cavity number, and registration feature used during labeling or print application.
The Standard capacity is the normal, or commercial, volume of a bottle. When a bottle is filled to standard capacity, the contents usually fill to the shoulder area of the bottle. The overflow capacity, or maximum fill, is measured to the very top surface of the bottle.
It is important to be sure you’ve selected the proper configuration for your application, manufacturing specifications and desired consumer experience, so if you need assistance, or for more information, please contact one of our Packaging Specialists. Illing Packaging is dedicated to Packaging Your Vision.