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11 Advanced FAQs About Glass Bottles for Essential Oils (With Answers!)

by Steve Carow  |   Oct 10, 2017

essential oil bottle

You should always feel confident about the quality of product you place on the shelves. Your customers rely on your brand for the best of the best, and your packaging needs to match that demand.

If you're looking for more advanced answers to your questions specifically about glass bottles for your essential oil products, you've come to the right place.

To ensure your brand puts its best foot forward in packaging your essential oils, we'll cover some of the most frequently asked questions I encounter with potential customers––and give our best answers to each.

18 DIN neck for glass bottles for essential oilsGCMI neck for essential oil bottles

Left: Dropper bottle with 18 DIN neck and tamper-evident transfer ring

Right: Boston round with GCMI neck

1. Why do I need to use dropper bottles when I already use and have Boston round bottles?

Dropper bottles feature an 18 DIN neck which can accommodate dropper inserts like EuroDrop® and provide a compatible transfer ring for tamper-evident caps. 18 DIN caps and bottle necks are designed for each other for the best performance. Additionally, the overflow capacity of dropper bottles will accommodate dropper inserts without overflowing. Dropper bottles with capacities ranging from 2.5 ml to 200 ml all have the same 18 DIN neck size.
This makes sourcing caps and dispensers easier because any 18 DIN cap will fit any 18 DIN bottle. Boston round bottles, on the other hand, feature GCMI neck finishes of 18-400, 20-400, 22-400 or 28-400, depending on the capacity of the bottle. The differing bottlenecks makes sourcing dispensers a challenge.
There is usually not a standard ID of the neck, so orifice reducers can be challenging. Tamper-evident caps are not possible with Boston round bottles due to a lack of compatible transfer ring. Carow Packaging has dropper bottles with the same height, diameter, and label panel profile as standard Boston round bottles––but substituting the 18 DIN neck for added dispenser options and functionality.

2. Which is the best color of glass bottles for essential oils?

Glass dropper bottle choices include: amber, blue/cobalt, clear/flint, and green. Of these options, amber is best if you are concerned about ultraviolet protection. The other colors have become popular because most glass bottles are stored in a dark environment––so UV protection is not usually a top concern. While dark bottles like blue or violet may limit visible light they lack the UV protection of amber glass. At Carow, we provide dropper bottles in all colors and can even spray coat bottles.

3. What's the difference between nominal capacity and overflow/brimful capacity?

Nominal capacity is the commercial designation of the bottle for selling purposes––30ml, 1-ounce, etc. We usually measure this in milliliters (ml), cubic centimeters (cc), or ounces (oz). In other words, nominal capacity is the industry-wide standard for the space inside the container for a given amount of product. When filled, it typically reaches the shoulder area.

On the other hand, overflow/brimful capacity is what you would fill to if you wanted to reach the brim of the bottle to reach the maximum capacity of the bottle. This usually never happens but is used to better understand other factors like determining the fill level, is there enough head space to accommodate dropper inserts, or is there adequate space to accommodate displacement for dropper pipettes.

4. Can I use Boston round bottles instead of dropper bottles for good dispensing?

glass bottles and caps for essential oils

In short, yes––you could use Boston round bottles instead of dropper bottles. However, you lose the dispensing benefits of the cap and dropper, such as the EuroDrop system. You will probably have leakage issues with Boston round bottles that you could definitely alleviate with the proper dropper bottle and cap/dropper insert combo. I would argue using Boston rounds to dispense something like essential oils is like selling a tricycle in a world of bicycles.  


5. Do I need child-resistant caps?

Yes, for certain flavors. There are many different philosophies behind this, and Carow has the knowledge and expertise to help you navigate your choices here. You'll need child-resistant caps on flavors as dictated by the Poison Prevention Act, which is regulated by the Consumer Product Safety Commission (CPSC).


6. What's the difference between orifice reducer and dropper insert?

An orifice reducer will only restrict the flow with one hole in the plug. The air tube of a dropper insert allows air to enter the container in addition to the orifice that lets the liquid out of the bottle. An orifice reducer does not have the air tube feature. A dropper insert, with a 4-part combination of controlling the liquid entrance/exit, air tube length/orifice, can offer much more control over the dispensing.

7. Which is the best––horizontal or vertical dropper?

Vertical droppers (right image) dispense when you turn the bottle upside down. They can offer a precise drop according to the viscosity of the oil. Horizontal droppers (left image) use the rim for dispensing and can give the end-user a more variable control. This could lead to slightly messier dispensing than with the vertical dropper. Both styles have been used successfully on millions of dropper bottles for decades. Carow Packaging can supply either style.

horizontal dropper insertvertical dropper insert

Left: Horizontal dropper insert

Right: Vertical dropper insert

8. Does my glass type matter?

The type of glass you choose only matters if you're pharmaceutical and need Type I. Dropper bottles typically are Type III glass and are suitable even for the highest grade of essential oils.

9. Is mixing Chinese and German components a problem?

In terms of volume, we're most successful right now using Chinese bottles and German caps. The Germans often have extremely high standards and quality of factories. This includes factors like consistent raw materials, more precise manufacturing equipment, centuries of experience, and extensive quality checks. The Chinese bottles offer great value but can present problems if you require high-speed production. At Carow, we pick the best suppliers depending on your needs. We have relationships with Chinese, European, and American suppliers of caps and bottles. Additionally, we produce some of our own caps and dropper inserts in the U.S.

10. What are the cost differences between working with a local distributor and doing it myself?

That’s the million-dollar question. You might have the resources to manage the manufacturer relationship yourself, but you might not. What is your time worth? Do you have the expertise to solve the inevitable manufacturing issues that will arise? Sometimes you pay more to work with a supplier, but it costs you less in research time and troubleshooting.

It's the same concept as this theory: You could make ketchup at home for less money––but you choose not to. Why? Your time is better spent focusing on your core competency.

Working with a local distributor, you get many benefits: speaking the same language as your main contact, working in the same time zone, better understanding of the quality factors that are most important to you, and access to in-person meetings. You also get quicker delivery, regional warehouses for closer shipping, and local help for technical or quality issues. This also eliminates the headaches that come with international transport. Ultimately, working with an expert local supplier will allow you to focus on your core business competencies.

11. Can I get essential oil caps made in the USA?

Carow is the only manufacturer of EuroDrop in the USA and is in the process of expanding those offerings. We also stock caps from Germany and have options from China.

To Wrap It Up:

Hopefully these answers will assist you as you research and choose glass bottles for essential oils. From the glass type to the restrictions around child-resistant caps, the devil is in the details.

If you have questions about any of the answers above, don't hesitate to contact us. Whether you need expert guidance on capping and filling or you just want to explore a more cost-effective option for your current supply, we're happy to help.


Essential Oils

Steve Carow

Author: Steve Carow

Since 1993, Steve has developed a comprehensive knowledge of dispensing, including sales, operations, information technology, and product development, which he applies when identifying customer solutions. He is the President of Carow Packaging and our representative for Midwestern US & Central Canada Sales.



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