After working for months and years to develop your brand and build your distillery, you know that packaging is a vital element of selling your final product. But in many cases, the design of the closure is often left to the last minute. The closure is one of your product's critical components and typically the only "moving piece" your customers will interact with. You want to wow them as they hear the tail tale "pop.
Beyond the role of wooing your customers, the closure has a significant job to do! It will seal your hard work in the bottle, keeping it safe and fresh during transport and while in storage. So you need to have a closure that sets you apart from your competition and fits your bottle well.
I will do my best here to summarize the process for choosing a closure (often called stoppers) for high proof spirits.
Types of Closure
Bar-top vs. Screw Cap:
Your stopper will need to match the bottle you select. There are two types of glass bottles finishes for distilled spirits. The first "finish" (bottle entrance bore) is the bartop or plate finish. The top of the bottleneck is smooth on these bottles, and a closure with a stem is needed.
The second finish is the GPI or screwcap; these bottles will have threads that a cap will screw onto. It will look similar to a water bottle with a screw-on cap. Screw caps do not have a stem and can have tamper seals built into them depending on the type of cap you go with.
Regardless of the type of finish, your closure will play a functional role in your design by sealing your bottle, so it is vital to select the best fit for your bottle. I am going to focus on bartop closures from here on out.
Components of the Bartop Closure
Unlike the screw cap, the bartop closure has two facets that you need to be aware of in your design.
Exterior Cap
Interior Stem (Shank)
The Cap:
The cap of your closure is what your customer sees and interacts with most frequently. Caps can be highly decorative or purely functional. The following materials are frequently used to make distilled spirit caps.
Wood
Plastic
Glass
Metal
Ceramic
Natural Cork
Synthetic Cork
The design possibilities for the cap are almost limitless, ever-growing, and a great way to show off your brand.
The Stem:
Choosing the right stem material and size for your bottle, proof, and type of spirit is vital to your product, having a tight seal for years to come. There are many intricacies that you need to consider when selecting your stem material. I recommend speaking to a closure company for this part as it can get complicated. There are three primary materials stems are made of, but more options appear on the market each year.
Natural Cork - this is a classic stem material that is sustainable and flexible, providing a tight seal for many years. It is best suited for dark spirits but can be coated for use with light spirits.
Agglomerate Cork - this stem is cost-effective, sustainable, and versatile. It is best used in dark spirits with lower proofs.
Synthetic Cork - this plastic material is a staple of the spirits industry. It can be used with almost any spirit and is relatively inexpensive.
Planning
If you are looking to stand out, plan ahead.
Try to have all aspects of bottle design complete six months before you plan to bottle. That's right, a full half-year before bottling! Why so long? Industry-standard lead times for non-stock closures can be produced in 10-12 weeks (that's almost three months)!
You can help speed the process along by having a clear idea of what you want your closure to look like when you first meet with closure companies. Have any logo or design ideas available to share, and bring up brands or closures that inspire you! You can also reach out early in the design process, as many closure companies can make recommendations about what to look for in other components of your packaging.
If you can't wait, some standard closers can be shipped much quicker. Most closure companies keep a limited catalog of closures that can be shipped within 1-2 weeks. However, these will be off-the-shelf solutions that will not express your brand to your customers.
If you are looking to stand out, plan ahead. Sampling alone can require a back-and-forth process that can take weeks to complete. You should also be aware that factories often have shutdown periods around major holidays and during the summer that can affect production. To avoid disappointment, don't leave packaging to the last minute.
Remember that certain items need to be taken into account when designing packaging. A creative designer can come up with a brilliant design that works well from a marketing standpoint but can have functional problems.
Tolerance
Closures and glass bottles have a tolerance range depending on the manufacturer and manufacturing method. These tolerance considerations can be extreme and vary from lot to lot.
Glass bottle specifications generally indicate the tolerance range, but it is always good to send the closure company at least one or two sample bottles. If the bottle design changes, send them a new bottle. Not only so they can have it on file for sizing but also for future questions or changes.
To avoid any surprises down the road, I would advise sending an updated glass bottle from each new lot. Over time the inside diameter of the bottle can change while remaining within the acceptable tolerance spectrum. An updated bottle will mean that the closure can be adjusted as needed for each new lot.
Fill Level
One of the most common issues that we see is bottles being overfilled. Glass bottles that have been professionally designed and manufactured have a specific fill line. Filling above that line can cause the closure to "pop up."
Headspace refers to the space between the closure and the liquid. This volume of air must meet a minimum threshold. When there is not enough headspace, during warm weather, high seas, or a bumpy road during domestic transport, the air's expansion will put pressure on the cork and push it up out of the bottle. In extreme cases, it can even cause your tamper seal to break. Review the glass bottle technical diagram, take note of the fill level, and any minimum/maximum threshold.
Tightness
When you first get your closure, you may think that the stem is too large, as it is difficult to place in the bottle. This fear is especially common for synthetic cork stems. You want your closure to be very tight upon initial insertion. The closure is fresh from production and has not been compressed at all. Over time, the stem will condense, causing what feels like a desirable seal initially to get loose, even allowing some of your product to spill out!
The humidity in the bottle can also soften the stem, which, combined with repeated removals and insertions, will lubricate the bottleneck making it easier to place the closure.
When in doubt, test a bartop by inserting it into a bottle filled to the appropriate level with a spirit (not water). Invert bottle three times. Then remove and reinsert stopper five times. How does it perform now?
Final Results
Once you have your stopper, remember to review and evaluate it after your initial bottling runs. You will make changes, and that's okay! It will take time to get everything, just how you want it, even after careful planning. Talk to your closure company frequently about how things are going and take notes of any questions that you have, ideas for the future, and how many you will need next. Like everything else in the distilled spirits world, the closure at every level of necessity is both a science and an art.