A star seal and a flat seal create different shapes at the bottom of a garbage bag. Choose between them by checking how the opened liner sits in the actual bin, then comparing leakage and lifting under the same conditions. The seal name alone cannot establish which finished compostable bag will perform better with your waste.
For a distributor replacing a liner, the question is often quite specific: will this construction reach the bin floor, stay on the rim and survive removal after the normal collection interval? A sample comparison should answer those questions before a buyer expands the result into a claim about a whole product range.
Open the bottom before comparing the labels
A conventional flat seal runs straight across the flattened bottom of the bag. Open the bag and the joined edge remains part of a relatively broad bottom shape. A star seal is formed with folds gathered into the bottom sealing arrangement; the opened base distributes that folded material differently.
NAPCO's explanation of can-liner bottom seals illustrates these structures and distinguishes them from a gusseted flat seal. Its descriptions concern its liner products. They help identify geometry, but do not prove the strength or leakage performance of a particular compostable sample.
Ask the supplier to identify the construction on an actual opened bag. Terms vary across quotations, and a small catalogue photograph can conceal the folds. If a buyer and a supplier use “flat” to mean different things, a comparison table will look precise while describing two different constructions.
Inspect the inside and outside of the base. Locate the seal, the folds and any film extending beyond the sealed interior. Check whether apparent corners unfold into usable space or remain outside the load-bearing body. Photograph the empty sample opened over a plain background and keep the sample reference visible in the image.
HENSEIN-BIO's star-seal bin liner product is a relevant construction to discuss during sampling. Confirm its current finished dimensions and order-specific documentation rather than treating the product title as a test report.
Fit can change where the load goes
Put each sample into the intended bin and seat it at the bottom before folding the top over the rim. Look for a base suspended above the floor, tight film across a lower corner or a fold that prevents the liner opening fully. Those conditions change how the bag experiences the first items placed in it.
On a round bin, assess how the bottom spreads around the circumference. On a rectangular bin, inspect the lower corners and the route from the base up the walls. A construction that appears tidy in an empty bin may pull tight when a bulky item occupies one corner. Record the bin shape and dimensions, not just the litre or gallon label.
Rim retention matters too. If one sample slips into the bin during filling, a later lifting failure may be partly a fit problem. If a sample must be stretched over the rim, the opening has already been loaded before collection begins. Do not compensate by tying or clamping one sample differently unless that is the normal operating method for both.
There is also a difference between a liner supported by the bin and a bag carried independently. During storage, the container supports some of the contents. During removal, the bag and its closure must carry the load. Test both stages if both occur in service; a good fit while supported does not settle the removal question.
Match the samples before assigning a cause
Obtain the measured width, usable length and film-thickness information for each sample. Note material construction, closure type, printing and how the samples were stored. If those features differ, compare the complete designs and report the differences. A better result cannot automatically be attributed to the seal geometry.
This is especially important when replacing a conventional liner with a compostable one. A result from one polymer construction is not a transferable rating for another material. Likewise, an old approved bag and a new sample may have different storage histories. Keep that limitation in the record rather than treating both as equivalent because their nominal dimensions match.
Use samples drawn from more than one position in the supplied pack or roll. Label them before testing so a failure can be traced back to its source. A supplier-selected presentation sample can show the construction, but a purchasing decision needs a clear record of what was actually compared.
| Comparison item | Record for both constructions | What a mismatch prevents you concluding |
|---|---|---|
| Bin fit | Bin dimensions, rim allowance and whether the base reaches the floor | That seal type alone caused an improvement |
| Bag dimensions | Relaxed finished measurements and usable length | That equal capacity labels mean equal fit |
| Film | Stated construction and measured thickness information | That the comparison isolates bottom geometry |
| Trial waste | Contents, mass, shape and liquid component | That the same service demand was applied |
| Holding period | Time, support and environment | That leakage results describe the same exposure |
| Removal method | Grip, closure, lift and carrying route | That lifting outcomes are directly comparable |
Run leakage and lifting as separate checks
For a practical leakage screen, agree a contained setup, a representative fill and a holding period that reflects the intended use. Keep the bags supported in the same way. Use an appropriate catch tray and a clean, controlled surrogate where a simulated load is suitable. Document any test liquid and its quantity.
Observe the first evidence of leakage and the location. A wet patch at a folded base, a hole in a side panel and liquid escaping through an incompletely closed top are different outcomes. Mark the location before moving the bag if movement would make it difficult to identify. Photographs are useful when they show the sample label and the failure area clearly.
An empty-bag liquid check can help investigate a suspected hole or seal path. It does not reproduce every effect of the real contents, dwell time and removal routine. Keep the investigation separate from the application trial so the reader of the report knows which question each check answered.
For lifting, prepare a fresh sample if the leakage investigation has altered or damaged the first one. Use the intended closure and grip. Record removal from the bin, the carrying distance or handling sequence and the condition at the end. Inspect the base and side panels as well as the top opening.
Avoid a single pass/fail label for the whole exercise. A bag can retain a liquid surrogate while supported and still tear during removal. Another can carry a dry bulky load but leak through a small defect. The purchasing record needs both outcomes if the operating task includes both demands.
Separate a practical screen from a laboratory seal test
A hands-on liner trial is a way to compare finished bags in a defined application. A laboratory seal-strength result addresses a different measurement. ASTM F88/F88M, for example, covers force measurements on specimens containing a seal and identifies failure modes. Its public scope does not turn a bin-and-lifting exercise into an ASTM test.
When a supplier submits a laboratory result, ask which part of the bag was sampled, how specimens were prepared and which method and edition were used. Review the reported units and failure description. A force value without the specimen basis is difficult to compare with another report.
Use laboratory work to investigate a question the application trial has revealed. Repeated separation along a specific joined area may justify targeted examination. Film tearing beside an intact seal raises a different question. Do not request a stronger seal merely because every failure occurred near the bottom; first determine what actually separated or tore.
The same caution applies to a “leakproof” description. Specify the conditions behind the claim and the evidence required for your use. An attractive seal diagram cannot establish performance through an undefined period with unspecified contents.
Let the waste profile set the trial emphasis
For wet, dense contents, the holding period and the supported-to-lifted transition deserve close observation. Identify how liquid collects and whether contents settle into the base. Include the normal interval between filling and removal so the test does not approve a bag for a shorter task than the operation requires.
For bulky dry waste, check how the objects spread the base and press against corners. Record contact points and whether packing staff normally compress the contents. Avoid adding hard or sharp test objects solely to make one sample fail; the surrogate should represent the agreed application.
If the real waste contains sharp items that can puncture film, review the collection method as well as the bag specification. A different bottom seal cannot remove a puncture hazard elsewhere in the body. Keep that decision with the site's waste-handling requirements instead of extending a general-purpose liner claim into an unsuitable task.
Collection acceptance is another separate requirement. Where a compostable liner is intended for an organics program, check the receiving operator's requirements for the bag and its contents. A satisfactory lifting result cannot establish compostability, and a compostability document cannot establish that a particular collector accepts the liner.
Interpret a result without overstating it
Suppose two sample designs fit the bin, but the flat-seal design develops a leak during the holding stage while the star-seal design does not. That is a useful observation for those samples. Before selecting the next action, inspect the leak location and the other differences in the two designs. A single film defect would support a different follow-up from repeated separation at the same sealing feature.
If the star-seal design leaks less but needs a larger overall bag to fit the operation, compare the resulting packing, material use and quotation on the same finished specification. The seal choice is part of a complete liner decision. The result should identify the design approved for the task, not establish a universal ranking of seal names.
Agree acceptance criteria before a broader trial. Name the unacceptable failure, the observation method and the person responsible for recording it. If the samples perform differently from one carton or roll to another, keep that variation visible and discuss further sampling. Do not remove inconvenient results from the record to produce a tidy average.
Put the chosen construction into the inquiry
Use the compostable garbage bag and bin liner range to identify the available product formats for discussion. Include an opened-bottom photograph, the bin measurements, usable bag dimensions, closure method and a description of the waste and collection routine.
Attach the comparison record with failure locations and sample references. State which dimensions or construction features you want kept constant in another sample round. If a change resolves one failure but creates a fit or removal problem, retain both observations.
Send HENSEIN-BIO your bin-liner specification and trial requirements. A clear application record allows the next sample discussion to focus on the construction and conditions you need assessed, with performance claims limited to the evidence available for that finished bag.