Quick Answer
A concave shampoo bottle base is a design feature, not a guarantee of stability or easier emptying. Approve the complete filled pack by checking its standing surface, rocking, tipping during normal handling, and behavior on the intended filling line. Compare samples at full, partly used and near-empty levels.
The useful sourcing question is not whether a recessed base looks better than a flat one. It is whether the actual bottle, formula and closure remain usable together. Treat material reduction, strength and residual product as separate outcomes that require evidence.
Define the standing surface first
Ask the supplier for the base drawing and identify which ring or feet are intended to contact the shelf. A raised central area should not become an accidental contact point. Place samples on a known flat surface and inspect the contact pattern, rocking and visible distortion. Record the sample lot and, where available, mold identification so an isolated result is not confused with the whole design.
Do not compare an empty lightweight bottle with a filled reference and attribute the difference entirely to base shape. Keep the formula fill, closure and pump configuration consistent between candidates.
Test the complete pack in its intended setting
Prepare a short trial sheet before handling samples. Include the fill level, surface, cap position and action. A bathroom shelf, an uneven shower ledge and a conveyor can reveal different problems. Select conditions that reflect the product’s intended use rather than deliberately extreme conditions with no agreed acceptance criteria.
- Full pack: assess placement, rocking and normal opening or pump actuation.
- Partly used pack: repeat with the same closure and handling sequence.
- Near-empty pack: check whether the pack needs support during actuation and whether the chosen storage orientation is realistic.
- After agreed conditioning: repeat the standing check and inspect any persistent base deformation.
Record the action that caused movement, not just a pass or fail. If a pump force tips the pack, the corrective discussion should include actuator force and overall geometry, not only the recessed bottom.
Separate dispensing from standing stability
A stable bottle can still leave product behind. Check emptying using the intended formula and dispensing system. For a dip-tube pump, examine the actual tube position; for a squeeze bottle, use the intended consumer orientation. Weigh the remaining product under an agreed procedure if residual content matters to approval. Do not claim that a concave bottom automatically channels every formula toward the outlet.
Run the line trial before freezing the tooling
Ask the filler to evaluate the sample on the relevant guides, transfer points and holding fixtures. Record speed and setup with the observed behavior. A hand-held approval does not establish reliable transport through the line. Preserve the accepted sample and drawing revision; repeat affected checks if the base geometry or material specification changes.
Create a standing and line-trial matrix
Assign each bottle a component revision, fill condition and closure identity. Record the actual standing surface and action used in the trial. Keep a clean reference so a later rocking result can be compared with the starting condition rather than remembered informally.
| Trial situation | Observe | Context to retain |
|---|---|---|
| Initial placement | Contact and rocking | Surface and assembled configuration |
| Normal dispensing | Movement and need for support | Fill level and actuation method |
| Line transfer | Guide contact and interruptions | Fixture and setup identity |
| After conditioning | Persistent changes in standing | Sample history and observed deformation |
Compare more than one relevant fill stage using the same procedure. Keep standing behavior separate from residual-product measurements. A candidate should not receive an emptying claim simply because it remains upright during a handling demonstration.
Investigate tipping without blaming the base alone
For example, a partly used bottle may stand without rocking but tip during pump actuation unless held. This illustrative result calls for review of the whole dispensing task. Preserve the filled assembly and record where the user applied force and how the bottle was positioned.
Ask the responsible team to compare the actuator, overall geometry and standing contact before selecting a correction. If a base revision is proposed, identify it separately and repeat the relevant placement, dispensing and line checks. A change that helps one task may still need review at a transfer point.
Handover the accepted geometry
Keep the base drawing and signed sample with the bottle, closure and fill configuration. Include any limitation that remains, such as a required holding method or an untested line setup. The filler should know which conditions the approval represented.
If tooling, material or assembly changes later, identify the affected trials before accepting the replacement. Compare production-intent samples rather than a drawing alone. The record should support reproduction of the accepted pack, not a universal claim that a recessed bottom is better.
Where a line trial is incomplete, retain it as an open action with an owner. Do not treat a successful shelf demonstration as completion of a different production-handling requirement.
Questions to settle before approval
Does a concave bottom always use less plastic? No conclusion should be drawn from appearance alone. Compare actual component weight and the approved performance results.
Is a flat base necessarily unstable? No. Judge the complete design and intended handling conditions.
What should accompany the approved sample? The base drawing, material specification, fill and closure configuration, trial conditions, observed results and any limitations.
Use the sample approval checklist to keep the evidence with the sample. For a sourcing discussion, share the bottle format and intended filling conditions.