The Truth About Round Plastic Containers And Their Finishes

Neck finishes tend to confuse people, and with good reason. What do two seemingly random numbers separated by a dash have to do with the finish measurements of round plastic containers and closures? More than you think. Read on to learn how to identify finishes and how that information will ensure a successful packaging experience.

A product’s finish analysis

Let’s use one of our lids as an example. The L160 has a 28-410 neck finish. The first number in the finish is the diameter of the closure (calculated in mm, measured from inside to inside the lid; neck finishes on round plastic containers are measured from outside to outside). The second number notifies users of the closures’ or round plastic containers’ thread count and height.

Here are the basic conversions of thread counts to finish numbers.
• 1 thread turn – 400
• 1.5 thread turn – 410
• 2 thread turns (Tall) – 415
• 2 thread turns (Narrow) – 425
• Thick threads/buttress finish – 430
• Lug finish – 2,000 (not continuous thread)

According to this conversion our 28-410 lid should have a 1.5 turn thread count. And as it turns out, it does!

Characteristics of a Finish

You know the basics of finishes, but sometimes that’s just not enough. For those who wish to know each and every minute detail of round plastic container finishes dive into their additional finish landmarks and details.

• T Area – This area includes the portion of the neck that reveals the diameter of round plastic containers. The 28 in 28-410, for instance.
• I Area – This measurement describes the inside measurement of round plastic containers. Without this measurement we could never be sure whether or not certain sized dispensing closures could pass through the opening of a certain bottle.
• S Area – The smallest section of round plastic containers’ finishes. It spans from the top of the opening to the first thread.
• E Area –The diameter measurement of a container’s neck from outside to outside, can be used to calculate thread depth with the T Area is also available [(T-E) ÷ 2 = Thread Depth].
• H Area – Denotes the height of round plastic containers from the very top of their opening to the place where a lid would sit, virtually the entire height of the container’s neck finish.

The unknown roots of container finishes

The concept for measuring the finishes of round plastic containers wasn’t revealed to someone in a dream or tediously crafted by a genius. Nope, this system came about when the big guys on campus from GPI (Glass Packaging Institute) and SPI (The Society of Plastics Industry) got together with hopes to create a uniform system for measuring the finishes of both round plastic containers and glass containers of different shapes and sizes.

By now you probably feel as if you know everything there is to know about round plastic containers and their finishes, but you’d be wrong. The number assignment of a finish is merely one detail. Check out my previous post on container finishes, “The multithreaded world of container finishes,” to learn more.

If round plastic containers inspired their own episode of Jeopardy, you would dominate the finishes portion. But with a busy lifestyle in mind, we’ve done the work for you by pairing compatible round plastic containers with appropriate closures, just browse through our “Matching Items” selection to find the perfect fit. You have a vision of finished product line, so go ahead, finish it, we’ll be here to help out along the way.

By: Kayla Holman

Article Directory: http://www.articledashboard.com

Do you know the neck finish of the round plastic containers you’re using? Read Kayla Holman’s article and learn how to measure the neck finish of round plastic containers.