Midwest Bottles 101

Please check out the packaging guides below. There will be more to come soon! In the meantime, if you have a question, please call us at 1-866-436-6373.

• Guide to Finding the Correct Cap Size "Finish"
• Types of Liners (Seals)
• Plastic Packaging Recycling Codes and Typical Plastic Properties

Guide to Finding the Correct Cap Size "Finish"

Choosing the correct closure or "cap" is a very important step of the packaging process. Plastic and metal closures come in a variety of sizes, styles and colors.

In the packaging industry the word "finish"is used to refer to the material surrounding the neck opening of any container or the inside dimensions of a cap. You'll often see finish sizes written in a format such as 24/410 or 24-410. There are two important parts to this number: the first number, 24, refers to the diameter in millimeters. The second part refers to the thread count. Below, we'll explain how to get these measurements.

The first number you need to find is the diameter. This measurement must be in millimeters (mm).

For a bottle: Measure from the outer edge of the thread on one side to the outer edge of the thread on the opposite side. For example, if the neck measures 24mm, then know it requires a 24mm closure.

For a cap: Measure from the inside wall of the cap to the opposite inside wall.

The second number refers to the thread count. If the thread loops around the neck and passes over itself one time, this is considered a 400 finish. If the thread passes over itself one and a half times, it's considered a 410 finish. If a thread passes over itself 2 times, it's a 415 finish. These are just a few of the most common thread counts.

We highly recommend testing your products with packaging samples to determine proper compatibility. If you need further help please contact our friendly staff.

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Types of Liners (Seals)

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Plastic Packaging Recycling Codes and Typical Plastic Properties

	Polyethylene Terephthalate (PET)	High Density Polyethylene (HDPE)	Polyvinyl Chloride (PVC)	Low Density Polyethylene (LDPE)	Polypropylene (PP)	Polystyrene (PS)	Other Plastics
Properties
Clarity	Clear	Translucent	Clear	Translucent	Translucent	Clear	Plastic ID Code "7" is for other plastics
Moisture Barrier	Fair to Good	Good to Excellent	Fair	Good	Good to Excellent	Poor to Fair
Oxygen Barrier	Good	Poor	Good	Poor	Poor	Fair
Max Temp	120F	145F	140F	120F	165F	150F
Rigidity	Moderate to High	Moderate	Moderate to High	Low	Moderate to High	Moderate to High
Resistance to Impact	Good to Excellent	Good to Excellent	Fair to Good	Excellent	Poor to Good	Poor to Good
Resistance to Heat	Poor to Fair	Good	Poor to Fair	Fair	Good	Fair
Resistance to Cold	Good	Excellent	Fair	Excellent	Poor to Fair	Poor
Resistance to Sunlight	Good	Fair	Poor to Good	Fair	Fair	Poor to Fair

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