The interlocking structure of stackable tea tins treats each layer as part of a unified mechanical system rather than an independent container. We first determine the tea-tin diameter, number of layers, fill weight, opening mechanism, and required stacking height. Next, we design the geometric fit between the upper and lower cans, including shoulder positioning, bottom grooves, contact surfaces, and gaps between adjacent layers. During the design process, TSING evaluates connection stability, separation force, wobble, dimensional consistency, and molding tolerances before prototyping. Therefore, a successful stackable tea tins design must achieve three objectives simultaneously: precise alignment, stable stacking, and easy separation during daily use.

The Stackable Tea Tins Design Begins with the Geometry of the Interlocking Layers

The basic function of an interlocking tea tin structure is simple: the upper container must sit precisely on the lower container without sliding arbitrarily or becoming difficult to separate. To achieve this consistently, the mating surfaces of the upper and lower containers must be designed as a single unit. Therefore, TSING develops the connection-point geometry before finalizing decorative embossing, printing, or other non-functional details.

The Stackable Tea Tins Design Utilizes Matching Upper and Lower Alignment Features

The connection between layers of stackable tea tins typically relies on complementary structural features rather than flat contact surfaces alone.

Common structural design elements include:

• A raised alignment shoulder around the top of the lower tea can
• A matching recessed area on the bottom of the upper tea can
• Controlled peripheral contact surfaces
• A specific insertion depth that restricts lateral movement

When an upper tea tin is placed on a lower unit, the bottom groove engages the positioning features below. This design ensures consistent alignment and prevents the cans from sliding against one another. For round tea tins, the positioning features can take the form of a continuous circular contour. For square or rectangular stackable tea tins, corner rounding radii and straight-wall alignment are critical.

TSING also considers the disassembly method. Stackable structures do not necessarily need to operate like “snap-fit” closures. In many tea packaging applications, a better solution is a “controlled positioning fit”: one that ensures stable alignment during handling while allowing consumers to remove a layer effortlessly.

Stackable Tea Tin Design Requires a Balance Between Inter-Layer Tightness and Clearance

The fit between layers is one of the most critical aspects of the entire structure.

If the interlocking areas are too loose, the upper tea can may shift laterally, resulting in noise, misalignment, and unstable stacking. If they are too tight, users may need to pull or twist with force to separate the layers; furthermore, normal manufacturing tolerances may make the fit noticeably tighter on some products than others.

Therefore, TSING has designed controlled clearances between mating surfaces rather than using zero-clearance connections. The required fit depends on various factors, including tinplate thickness, diameter or overall footprint, the depth of the positioning structure, forming processes, surface coatings, and printing, among others. Contact-area design is also crucial. When designing stackable tea tins, TSING evaluates these variables comprehensively rather than adjusting a single dimension.

For multi-layer tea can packaging, our design goal is to achieve a structure that provides both reliable positioning and a smooth sliding fit—avoiding both uncontrolled loose stacking and unnecessary forceful mechanical locking.

Preventing Wobble Through Multiple Contact and Alignment Points

Wobble typically stems from excessive radial clearance, insufficient insertion depth, uneven contact surfaces, or accumulated dimensional deviations. Therefore, simply increasing the fit tightness is insufficient to achieve stable stacking. TSING first verifies that the upper container is positioned on a clearly defined support surface. Loads should be transferred through predetermined structural areas, rather than through random contact points caused by deformation or uneven molding.

We pay attention to the following design details to enhance stability:

Adequate positioning depth between layers
Uniform support around the mating edges
Controlled radial clearance
A flat and rigid base plate
Symmetrical molding at the stacking interfaces
Appropriate corner radius for non-circular containers
Sufficient structural rigidity for the anticipated load weight

For stackable containers, reducing wobble requires a careful consideration of interlocking geometry, panel rigidity, dimensional consistency, and overall packaging proportions.

The Stackable Tea Tins Design Requires Strict Control of Manufacturing Tolerances and Validation

Even if the structure appears flawless on 3D drawings, actual performance may still be inconsistent if critical fit dimensions change during the forming process. Processes such as cutting, stamping, flanging, can body forming, seaming, coating, and tinplate assembly all introduce normal manufacturing deviations. Therefore, TSING clearly identifies the key dimensions that directly determine interlocking performance and controls them strictly.

The Quality of an Interlocking Structure Design Depends on the Control of Key Fitting Dimensions

Not all tea can dimensions require the same level of strict control. For interlocking structures, the most critical dimensions typically include the following:

1. Outer diameter of the positioning shoulder
2. Inner diameter of the mating groove
3. Engagement depth
4. The height of the support step
5. The flatness of the can bottom
6. The roundness of the lid or body of a cylindrical can

These dimensions determine whether products from different batches can maintain a stable fit between layers when stacked. TSING also considers the cumulative effect of tolerances. A minor deviation in a single component may fall within acceptable limits. Still, if multiple deviations accumulate in the same direction, the stack may become too loose or too tight. For example:

Forming deviation + coating thickness + can bottom deformation + positioning feature deviation = actual interlocking fit

For this reason, stackable tea tin design cannot rely solely on nominal CAD dimensions; it must also incorporate mold capabilities and the characteristics of tinplate after forming. Determine specific tolerance values based on can dimensions, geometry, material thickness, mold processes, and production equipment.

Comprehensive Design of Interlocking Structures for Stackable Tea Tins

Tea capacity and number of layers → Determination of container dimensions → Design of interlocking geometry → Setting of positioning depth and clearance → Structural support design → Mold design → Prototype molding → Multi-layer fit testing → Tolerance adjustment → Mass production validation

At TSING, this process ensures stackable tea tins are more than containers you can stack on top of one another. A well-designed stackable tea tin ensures precise alignment between layers, minimizes wobble, maintains an appropriate separation force, and consistently delivers the same stacking performance throughout mass production.

Developing new molds for custom food tins starts with the product, not the mold-making process. At TSING, we first confirm the tin’s required dimensions, shape, lid structure, intended food use, internal layout, and exterior decorative details. We then translate the approved design concept into seven stages:

Custom Sample Drawing → Mold Structure Drawing → 3D Structural Drawing → Mold Contour Cutting → 3D Surface Forming → Mold Assembly → Pre-Production Prototyping

Before the mold goes into production, each stage verifies different aspects of the design. This systematic process enables TSING to identify issues related to dimensions, forming, sealing, and appearance early on, reducing unnecessary mold modifications and helping clients turn custom packaging concepts into food tins with stable performance ready for mass production.

Determining Product and Mold Design Requirements for Custom Food Tins

Before developing a new mold for custom food tins, we must determine whether a new mold is necessary and clearly define the packaging requirements it must meet. Mold development should not begin with machining; it should start with an assessment of the tin’s dimensions, shape, sealing structure, internal product layout, and existing mold resources. Once we clarify these requirements, we can decide whether to modify an existing mold or develop a completely new one. Next steps include gathering accurate product and packaging information, translating relevant requirements into feasible tin mold design solutions, and then moving through the full custom food tin mold development and design process—from creating structural drawings to mold manufacturing and sample validation.

When Is a New Mold Required for Custom Food Tins?

You need a new mold when existing production molds cannot achieve the desired shape, dimensions, structure, or functional details of the tin. For many custom food tin boxes, simply changing the printed design does not require a new mold. If a customer selects a round, rectangular, square, or irregular shape from the mold library, we can typically use the existing structure directly for design and prototyping.

However, if a customer requests structural changes, we must create a new mold. Examples include:

• Completely new dimensions for length, width, height, or diameter
• Unique lid or base contours
• Custom embossing or three-dimensional shapes
• Unique shoulders, curved side walls, rounded corners, or stepped structures
• Closed structures that cannot be produced using existing molds

Therefore, the decision to create a new mold should be based on geometric shapes and forming-process requirements, not solely on whether the packaging appearance is a custom design.

During the mold development and design phase for custom food tins, TSING first compares the customer’s requested packaging specifications with existing molds before recommending a new mold. This helps avoid unnecessary mold costs for the client, especially when existing, proven designs already meet the packaging requirements.

What Information Is Needed Before Developing a Custom Food Tin Mold?

Mold development accuracy depends on the precision of the product information. We cannot begin designing a tin mold based solely on visual reference images.

Before initiating the engineering design process, we typically need to confirm details such as the required dimensions and shape of the finished tin box, as well as the desired lid structure. For food products, the contents themselves often determine the critical dimensions. For example, a cookie tin design must account for the cookies’ diameter, thickness, arrangement, tray layout, and required headspace. Even if tea tins and candy boxes look similar, their opening dimensions or internal volume requirements may differ completely.

Providing images of custom samples is usually the first practical step. This helps us understand the client’s expectations for the tin’s appearance and proportions before detailed engineering design begins.

TSING’s Mold Development and Design Process

After confirming the structure and requirements, we follow the process below to develop the mold, rather than proceeding directly to the metal-cutting stage. This process typically consists of seven stages.

1. Custom Sample Sketch:
The project begins with a visual rendering of the desired tin box. This helps confirm the overall shape, proportions, lid style, and key aesthetic features.

2. Mold Structural Drawings:
The visual concept is translated into structural mold drawings. At this stage, TSING evaluates the manufacturing methods for the tin box body, lid, base, edges, and forming areas.

3. 3D Structural Model:
A 3D structural model is then created to evaluate the geometry more precisely. This stage helps identify interference issues, improper proportions, forming limitations, and assembly risks before manufacturing the physical mold.

4. Mold Contour Cutting:
Once the structural design is approved, the mold components are cut according to the engineering specifications. The precision of this stage directly affects the consistency of the finished tin box.

5. 3D Surface Machining:
If the design includes curved surfaces, irregular contours, or three-dimensional features, the mold will be machined accordingly to accurately reproduce these forms.

6. Mold Assembly:
The team assembles and inspects mold components as a complete system. Before trial production, verify alignment, forming positions, and fit between mold components.

7. Pre-Production Samples:
The manufacturer produces physical samples using the assembled mold. Before formal mass production begins, the customer and manufacturer can inspect the actual tin cans.

Newly Developed Molds Must Undergo Validation Before Entering Mass Production

Completing mold fabrication does not mean custom food tins are immediately ready for mass production. Before we use the mold for large-scale manufacturing, we must validate it to ensure the tins meet the specified dimensions, structure, sealing performance, and product-fit requirements. This validation phase is critical because even minor deviations—such as lid fit, inner tray positioning, formed edges, or internal clearances—can cause issues during filling or mass production. Therefore, we use prototype samples to verify both appearance and functional performance and make any necessary adjustments before final approval.

How to Test Prototypes of Custom Food Tins?

Even if a prototype resembles the original design drawings, it does not guarantee approval. We evaluate samples as functional packaging; depending on the design, the prototype review may cover finished dimensions, the fit between the lid and body, and the smoothness of the opening and closing mechanism.

When testing prototypes, we place actual food items or dimensionally accurate substitutes inside the box whenever possible. For example, even if a prototype meets the external drawing requirements, modifications may still be necessary if the inner tray sits too high and prevents the lid from closing properly. Similarly, while the lid may look correct externally, it may turn out too loose or too tight after actual molding.

Therefore, prototype testing closely links the tin mold design with actual packaging performance.

Does Developing a New Mold Affect the Lead Time for Custom Tins?

Developing a new mold increases the initial time investment, as it must undergo multiple engineering design and validation stages before formal production can begin. For projects using existing molds, you can usually move directly to pattern design, prepress preparation, and production prototyping; new mold projects must first complete steps such as structural confirmation, mold drawing preparation, 3D modeling, machining, mold assembly, trial molding, and sample approval.

Therefore, the delivery process for new mold projects involving custom food tin boxes typically follows this sequence:

Requirement Confirmation → Structural Design → Mold Manufacturing → Mold Assembly → Trial Production of Samples → Sample Revisions (if necessary) → Approval → Mass Production

The lead time depends on the mold’s complexity. Tin boxes with simple geometric shapes typically require less development work than those with complex curved surfaces, embossing techniques, irregular shapes, or multi-part structures. Of course, the client’s preparatory work also affects the schedule. Providing complete dimensional data, reference samples, product specifications, and clear approval feedback reduces the need for repeated structural revisions and shortens the development cycle.

A Reliable Development and Design Process for Custom Food Tins

For custom food tin boxes, the most reliable development process is as follows:

Product Requirements → Custom Sample Sketch → Mold Structural Drawing → 3D Structural Drawing → Wire-Cut Mold → 3D Forming → Mold Assembly → Production Samples → Final Validation → Mass Production

At TSING, this process lets us develop custom molds based on real food and packaging requirements, rather than rigidly applying design concepts to unsuitable standard structures. Efficient mold development ultimately ensures that the produced tin cans feature stable manufacturing processes, proper filling compatibility, and reliable sealing performance.

The SCA notes that oxygen is the main factor causing roasted coffee to deteriorate (lose flavor), and that storage humidity also affects coffee quality. Therefore, when selecting a coffee can, the seal design is crucial. Two common seal designs are the “double-lid coffee tin” and the “gasket-sealed coffee tin.” The double-lid design creates two barriers between the coffee and the external environment. In contrast, the gasket-sealed design uses a compressible sealing element between the lid and the can body to minimize gaps at the closure.

Don’t choose between these designs based solely on appearance. At TSING, we evaluate and compare these two designs by comprehensively considering sealing performance, reusability, coffee characteristics, manufacturing complexity, and customers’ actual freshness requirements.

Coffee Tins Comparison: Differences Between Two Sealing Designs

When choosing between a gasket-sealed coffee tin and a double-layer lid design, one cannot simply compare the number of sealing layers. These two sealing designs differ in how they control air exchange; this difference affects not only the can’s resealing stability after repeated openings but also the consumer’s daily user experience.

Therefore, we will compare three aspects: the operating principles of the sealing structures, the ability to maintain sealing performance after repeated use, and whether the opening experience aligns with the target coffee product and brand positioning. These three factors form the basis for evaluating which coffee can structure best suits specific application scenarios.

Design Differences Between Gasket-Sealed Coffee Tin and Double-Lid Coffee Tin

Double-lid coffee tins combine an outer lid with an inner lid or a plug-type seal. Their primary advantage lies in creating multiple physical barriers:

Outer lid → Inner lid → Coffee Tin

When the outer lid is opened, the inner seal keeps the coffee isolated from the external environment until the consumer removes it. This structure suits specialty coffee, tea, and gift packaging. However, the double-lid design does not guarantee a completely airtight container. Actual sealing performance still depends on the following factors:

• Lid fit tolerances
• Inner lid fit
• Molding precision
• Contact area
• Repeated opening and closing operations

Sealing coffee tins with a gasket is different. When the lid closes, silicone, elastomers, or other suitable food-grade sealing components compress between the mating surfaces. This compression creates continuous contact around the sealing interface. Effective sealing depends on controlled compression, sealing-surface quality, dimensional tolerances, and the right material choice.

In terms of actual coffee tins:

Double-lid = Additional barrier layer

Gasket-sealed = Controlled compression at the closure

Gasket-sealed coffee tin provide better resealability after opening

Coffee packaging involves two distinct stages of freshness preservation.

The first stage is when the package is unopened. The second stage begins once the consumer opens the package daily. The second stage is often overlooked.

Whenever a consumer opens a large-capacity container, outside air enters and comes into contact with the coffee beans or ground coffee. We should minimize the amount of oxygen entering the container during repeated opening and closing.

For repeated use, gasket-sealed coffee tins offer significant advantages: as long as the sealing material, compression level, and lid geometry are properly designed, the gasket maintains pressure on the sealing surface every time the lid is closed. This makes them suitable for:

• Coffee beans for daily use
• Ground coffee
• High-end specialty coffee
• Coffee that needs to be stored for several weeks after opening

A double-lid design also provides a good seal, as the inner lid acts as an additional barrier. However, its performance depends largely on how tightly the inner lid fits. If repeated use loosens the fit, sealing performance may suffer.

Gasket-Sealed Coffee Tin vs. Double-Lid Coffee Tins: Different User Experiences

While sealing performance matters, packaging must also support the user experience. Double-lid coffee tins create a unique opening process: consumers must first remove the decorative outer lid, then open the inner lid, before accessing the coffee. This design is particularly well-suited for the following brand needs:

• Conveying a traditional, high-end feel
• Gift-quality packaging
• Providing additional physical protection

The double-lid structure also minimizes direct contact between the coffee and the outside environment when the outer lid is briefly removed.

In contrast, gasket-sealed coffee tins achieve a strong seal through a simpler opening process. They suit customers who need frequent daily access and a simple, one-step opening mechanism. So decision-making shouldn’t focus solely on airtightness. For high-end retail packaging, we also comprehensively consider closure performance, ease of use, and brand positioning.

Matching Sealing Designs to Coffee Types and Processing Methods

After comparing the two sealing structures, the next step is to match the design solution to specific coffee products and processing methods. Although gasket-sealed coffee tins offer more reliable resealability, required sealing performance varies based on several factors, such as whether the package contains whole beans or ground coffee, how often consumers open the can, and the time between roasting and packaging.

Therefore, before recommending a sealing design, TSING conducts a comprehensive assessment of the coffee’s form and production process. Ground coffee typically requires higher resealability standards, while freshly roasted whole beans release carbon dioxide (CO₂) continuously after roasting. Consequently, the following two factors must be evaluated:

For Ground Coffee and Applications Requiring Long-Term, Repeated Sealing

Sealing performance is especially critical for ground coffee, as grinding significantly increases its exposed surface area and accelerates the loss of gases and aromatic compounds. Therefore, when handling ground coffee packaging, we typically prioritize solutions with stronger sealing performance that can withstand repeated opening and closing.

Here is a practical selection guide:

Requirement	Preferred Starting Option
Frequent daily opening	Gasket-Sealed Coffee Tin
Ground coffee	Gasket-Sealed Coffee Tin
Strong repeatable lid compression	Gasket-Sealed Coffee Tin
Premium ceremonial opening	Double-Lid Coffee Tin
Additional inner physical barrier	Double-Lid Coffee Tin
Gift-oriented coffee packaging	Double-Lid Coffee Tin

A well-designed double-layer lid structure may outperform solutions with poorly designed sealing rings; conversely, if the lid structure cannot ensure even force distribution on the sealing ring, simply adding a silicone ring will not guarantee a good seal.

Therefore, at TSING, the final design must be tested as an integrated system, taking into account factors such as:

Can body + Lid + Sealing ring/inner lid + Dimensional tolerances + Actual repeated-use conditions

At the same time, we ensure the sealing ring material complies with food-contact safety standards; selection should not be based solely on softness or appearance.

The Issue of Gas Release from Freshly Roasted Coffee Must Be Considered

Both designs face a significant limitation: sealing strength alone cannot resolve gas release from freshly roasted coffee.

Coffee beans continue to release carbon dioxide (CO₂) after roasting. The outgassing process is particularly rapid during the first few weeks; studies have also confirmed that roasted green coffee beans continue to release gas. Depending on the customer’s specific requirements, the solutions we can provide include:

• Allowing adequate time for outgassing before filling
• Using inner packaging bags with one-way vent valves inside the can
• Developing other design solutions tailored to the project

Therefore, when communicating with clients, we focus not only on coffee weight and can size but also on the time interval between “roasting and packaging.”

So, which sealing method is better?

For brands that prioritize a secure seal, reusability, and controllable lid sealing, a well-designed coffee tin with a sealing gasket is typically the more suitable choice, as its compression-sealing element acts directly on the joint between the lid and the can body.

For brands that prioritize multi-layered physical structures, premium visual presentation, and a unique opening experience, double-lid coffee tins are the better choice. We recommend following this decision-making process:

Coffee beans or ground coffee → Time between roasting and packaging → Expected shelf life → Frequency of opening → Sealing performance → Brand experience

TSING will then match the appropriate lid structure, tolerance standards, sealing components, and can dimensions based on the above requirements. Therefore, the highest-quality sealed coffee tin does not simply depend on the container structure with the most layers, but rather on whether its sealing design can consistently maintain the level of protection required for the coffee throughout the entire process—from filling and storage to repeated use by consumers.

Many customers ask us, “How should we choose the custom tea tin sizes for 100g, 250g, and 500g of tea?”

Our answer is: Choosing a custom tea can size based solely on weight may result in an inaccurate package size. Two types of tea that both weigh 100 grams may have vastly different volumes. Research on refined green tea shows that bulk density (apparent density) varies by tea variety and filling method.

Therefore, when determining dimensions, we should comprehensively consider the following factors:

Net Tea Weight	Recommended Round Tin Internal Size	Equivalent Rectangular Internal Size
100g	Ø80 × 100 mm	90 × 65 × 85 mm
250g	Ø110 × 130 mm	120 × 85 × 120 mm
500g	Ø140 × 165 mm	150 × 110 × 155 mm

Tea weight + bulk density + headspace (top clearance) + lid structure

For common, moderately dense loose-leaf teas, TSING recommends the following initial dimensions:

The above are reference inner diameter dimensions, suitable for moderately dense loose-leaf teas. Before mass production, we will verify the final mold dimensions using the customer’s actual tea samples.

Custom Tea Tin Sizes Should Be Based on Tea Volume, Not Just Weight

To determine the right custom tea tin size, first convert the tea’s weight into its actual volume. Because bulk density varies by tea type, the required internal volume can differ significantly even for the same weight—whether 100g, 250g, or 500g. You must also reserve sufficient headspace to allow filling and, depending on the situation, allocate space for an inner lid, liner, or sealing mechanism. Therefore, for loose tea of medium density, establish reference dimensions first, then conduct actual filling tests.

The following three size ranges show how to determine custom tea tin sizes for 100g, 250g, and 500g of tea, balancing volume, packaging ratio, and filling efficiency.

Custom Tea Tin Sizes for 100 Grams of Tea

For standard 100g retail tea products, we recommend the following approximate circular inner dimensions:

Diameter Ø80 mm × Height 100 mm

Before accounting for the lid’s insertion depth or space taken up by internal sealing components, this size provides a cylindrical internal volume of about 500 milliliters.

The corresponding custom rectangular tea can sizes would be approximately:

90 × 65 × 85 mm

This size suits many medium-density loose-leaf teas, offering brands compact retail packaging while supporting filling and storage.

Round tea tins with diameters of 60–80 mm and heights of 60–100 mm are common retail specifications, though they also indicate that the density of whole-leaf tea can vary significantly. However, for extremely bulky tea leaves, the Ø80 × 100 mm size may not be sufficient. In such cases, we will increase the tin’s volume rather than force the tea leaves into the tin to fit a predetermined packaging size.

Custom Tea Tin Sizes for 250g of Tea

For retail or gift packaging in the 250g size, a practical dimension is:

Diameter Ø110 mm × Height 130 mm

This provides a total internal volume of approximately 1.24 litres.

An alternative rectangular shape could be:

120 × 85 × 120 mm

This size offers roughly the same usable volume and stacks more easily because of its shape.

The 250g size falls between small retail packaging and large family-size containers. For manufacturers, the key consideration is not simply doubling the dimensions of a 100g tin. Volume changes affect all three dimensions. Therefore, increasing both diameter and height usually yields better packaging proportions than making the tin excessively tall.

Custom Tin Sizes for 500g Tea

For 500 grams of medium-density loose-leaf tea, a practical size is:

Diameter Ø140 mm × Height 165 mm

This size provides a total internal volume of approximately 2.54 liters.

For rectangular tea tins, TSING recommends starting with dimensions of approximately:

150 × 110 × 155 mm

When the capacity reaches 500g, structural stability becomes particularly important. Because larger tea tins have a greater unsupported wall area and bear a heavier load, we need to evaluate design factors such as tinplate thickness, sidewall rigidity, bottom reinforcement design, lid fit, and stacking load capacity.

TSING typically uses tinplate about 0.23–0.30 mm thick for its tea can products; the specific thickness depends on the product’s dimensions, shape, and structural requirements. Therefore, when increasing the size of a custom tea can, we conduct a structural evaluation simultaneously rather than simply scaling up the design.

Custom Tea Tin Sizes Must Be Verified Based on the Actual Tea Leaves

While the recommended dimensions can serve as a starting point, they should not be treated as final specifications for custom tea tins. Before tooling or mass production, manufacturers must verify how the actual tea leaves fit inside the selected container. The shape of the tea leaves, their bulk density, the filling method, and the space taken up by the inner lid or sealing components all affect the container’s usable capacity.

Therefore, before finalizing the dimensions, TSING conducts a comprehensive assessment of the required headspace and the actual filling results. This approach helps avoid the following two common issues.

Allowing Adequate Headspace to Avoid Excessive Dead Volume

Tea tins should not be filled so tightly that the tea leaves touch the lid. Adequate headspace not only makes filling easier but also reduces the risk of crushing delicate tea leaves when closing the lid or installing internal seals. However, excessive headspace is also undesirable, as it increases:

• Packaging dimensions
• Shipping volume
• Shelf space occupied
• The amount of residual air inside the container

For standard custom tea tin projects, TSING typically starts with a moderate filling allowance and then verifies it using actual tea samples.

The formula for calculating the actual dimensions is as follows:

Required tea can volume = Tea weight ÷ Measured bulk density + Filling allowance. For example, if the measured bulk density of a particular tea is 0.20 g/mL, then:

100 g ÷ 0.20 = 500 mL

We then fine-tune the tea can dimensions based on the required headspace and the space occupied by the inner lid, liner, or sealing system.

Confirmation Through Actual Filling Tests Before Mass Production

The most reliable approach is to send the manufacturer actual tea samples. We recommend following this process:

Tea sample → Determine bulk density → Set target fill weight → Compare with existing molds → Conduct test filling → Check lid fit and headspace → Finalize dimensions.

This is particularly important when deciding whether to use existing molds or develop new ones.

TSING offers custom tea tins in round, rectangular, and other shapes, equipped with a variety of sealing methods, liners, and airtight configurations. For most loose-leaf teas of medium density, the following three initial specifications can serve as reference benchmarks:

100g: Ø80 × 100 mm
250g: Ø110 × 130 mm
500g: Ø140 × 165 mm

Corresponding rectangular specifications are as follows:

100g: 90 × 65 × 85 mm
250g: 120 × 85 × 120 mm
500g: 150 × 110 × 155 mm

Use these dimensions only as a starting point for production, not as a universal guarantee of capacity.

Determining the Final Custom Tea Tin Size

From TSING’s perspective, the correct method for selecting a custom tea can size is straightforward: start with the target weight, calculate based on the tea’s actual volume, allow for appropriate headspace, and verify the results through physical filling tests before mass production. This approach ensures that the produced tea tins are neither too large—which would result in waste—nor too small—which would compress the tea.

Two products might use metal cans of identical dimensions, tinplate thickness, and even exterior printing, yet still need to meet different specifications for food contact tin packaging.

The reason is simple: oily and acidic foods determine the specific resistance properties required for the inner surface.

Acidic foods subject the packaging to an environment that places extremely high demands on corrosion resistance and the integrity of the coating’s barrier properties. Fats and oils in oily foods interact with organic coatings in different ways, and food contact migration assessments must consider these interactions separately.

For applications involving oily foods, evaluations typically use edible oils or other suitable simulants, whereas assessment methods for water-based and acidic foods differ.

Therefore, professional manufacturers should not approve food contact tin packaging based solely on the claim that the inner coating is labeled “food-grade.” Specific technical specifications must match the actual food product, filling process, shelf life, and conditions of use.

The selection of food contact tin packaging must be based on the chemical properties of the food itself

The most important information when purchasing is not the tin can size, but the food formulation.

When selecting packaging, we need to determine whether the product contains the following components:

• Organic acids
• Free fats
• Salt
• Moisture
• Strongly flavored compounds
• Other potentially corrosive ingredients

The FDA itself categorizes food contact applications into different food categories. Its current food type classification table distinguishes between acidic water-based products, products containing free fats, low-moisture fats, and even dry solids with or without free fats on their surfaces.

This classification system offers important insights for tinplate packaging:

“Food contact” is not a one-size-fits-all application.

Consider the following two products:

Food	Main Packaging Challenge
Tomato-based seasoning sauce	Acid exposure and corrosion resistance
Nut or oil-rich seasoning paste	Oil/fat contact and migration compatibility

Both may require coated tinplate, but you shouldn’t assume they need the same coating system. This principle also applies to custom tin cans for sauces, candies, condiments, oil-containing snacks, candied fruits, and specialty foods.

Food Contact Tin Packaging for Acidic Foods

Acidic foods create a more corrosive environment for metal tin packaging, particularly when moisture, salt, organic acids, and long-term storage are involved. Therefore, the inner coating must not only visually separate the food from the metal; it must also maintain an effective barrier between the food and the tinplate throughout the expected shelf life.

For acidic products, we evaluate acid resistance, coating adhesion, and film continuity.

Our recent research on coated tinplate further underscores the importance of food formulations: ingredients such as citric acid, acetic acid, and salt—and even combinations with oily components—can affect coating degradation and tinplate corrosion in different ways. This means that selecting an interior coating solely because it performs well with dry or high-fat products may pose unnecessary risks when the same packaging is used for products with acidic formulations.

TSING’s approach is to first clarify the food’s chemical properties, then select a coating system suitable for the application in terms of both regulatory compliance and technical performance.

Food Contact Tin Packaging for Food Contact with Oily Foods

Oily foods create a unique food contact environment.

Fats and oils can act as effective media for extracting specific substances from polymer-based food contact materials. Therefore, the FDA recommends using specific oily food simulants when evaluating migration into oily foods.

The FDA’s chemical evaluation guidelines explicitly state that edible oils or other suitable simulants for oily foods may be used for applications involving oily foods. The guidelines also note that migration levels depend, to some extent, on the solubility of the food contact substance in the food.

Therefore, for tin packaging intended for oily foods, we evaluate the coating’s compatibility with fats and oils, as well as its stability during prolonged contact. Relevant products include:

• Fat-rich spice blends
• Nuts
• Fatty candies
• Seasoned sauces
• Oil-immersed products

A key distinction is that excellent acid resistance does not automatically imply suitable migration performance during prolonged contact with oily foods. Conversely, a coating that performs well in terms of oil resistance does not automatically imply sufficient corrosion protection for acidic, water-based formulations.

Matching Food Type, Time, and Temperature

Food type is only one aspect of the specifications.

The FDA also classifies food-contact applications by usage conditions, including hot filling, room-temperature storage, refrigeration, freezing, and high-temperature processing. Therefore, two identical foods—one filled at room temperature and the other requiring heat processing may require different validation conditions.

Consequently, professional tin can packaging specifications should define at a minimum:

• Food ingredients
• Contact surfaces
• Filling temperature
• Processing temperature
• Storage temperature
• Expected contact time

For example, a coating intended for a high-fat, dry food product stored at room temperature should not be automatically considered equivalent to a coating intended for an acidic sauce subjected to high-temperature processing. For this reason, FDA authorizations for food contact materials are tied to specific intended uses and conditions of use, rather than merely a general claim that a material is “FDA-approved.” The regulatory status of a finished food contact material depends on the regulatory basis for its individual components and its intended use.

H2: Validation Should Be Conducted Using the Actual Product Before Mass Production

For purchasers, the safest procurement process is very simple:

Do not start with the tin packaging; start with the food itself.

Before commissioning the production of custom tin cans, the following information should be provided to the supplier:

1. Product type and formulation
2. Approximate pH value under relevant conditions
3. Whether the product contains oils or free fatty acids
4. Salt content or other corrosive ingredients
5. Filling temperature
6. Heat treatment requirements
7. Target shelf life and storage conditions

The manufacturer can then select the appropriate tinplate substrate, inner coating, sealing method, and production control parameters based on these requirements. If the product has special chemical properties or stringent shelf-life requirements, consider representative compatibility or migration testing before approving mass production. Acidic foods demand higher corrosion resistance and barrier integrity, while oily foods require a focus on compatibility and migration characteristics when in contact with fats and oils. Additionally, time, temperature, salt content, moisture, and processing methods can further influence specific requirements.