To test a metal-free pump with your formula, fill it in your final bottle and check three things over time: how the pump performs, how the formula holds up, and how the package survives storage and shipping. Run tests at room temperature and under heat and cold, and compare results with a control. Your supplier's data is a useful start, but your own formula is the real test.
Why compatibility testing matters for metal-free pumps
Every pump is a small machine. It has a piston, a seal, a valve and a spring or return mechanism. In a metal-free pump, those parts are all plastic. That design removes metal parts from the product path, but it also means the pump's behavior depends on how the plastics work with your formula.
Oils, fragrances, solvents, surfactants and high or low pH can all affect plastic parts in different ways. Some formulas may cause parts to swell, soften or stick. Others may change how the pump primes or returns. None of this is unique to metal-free pumps, and the only way to know is to test.
Testing also protects your launch. A pump that sticks or leaks after a few weeks on shelf is costly to fix once product is in the market.
What to test: the three groups
A good test plan covers the pump, the formula and the full package. The table below shows common checks in each group.
| Test group | What you check | Why it matters |
|---|---|---|
| Pump performance | Priming strokes, dose per stroke, dose consistency, return speed, actuation force | Confirms the customer gets a smooth, steady dose from first to last use |
| Formula stability | Color, odor, viscosity, pH, separation, appearance in the dip tube and nozzle | Shows whether the formula changes in contact with the pump parts |
| Component condition | Swelling, softening, cracking, discoloration, sticking parts | Shows whether the formula affects the plastic parts over time |
| Package integrity | Leaks, weight loss, seal at the neck, lock function | Confirms the package holds the product through storage and use |
| Transit | Drop, vibration, pressure change, orientation | Important for e-commerce and parcel shipping |
How to set up your test
Keep the setup close to the real product. Small differences can change the results.
- Use your final formula. If the formula is still changing, test again once it is locked.
- Use your final bottle. The neck finish, bottle material and dip tube length all affect how the pump performs.
- Fill to your real fill level. Headspace affects leaks and pressure.
- Cap at your production torque. Under- or over-tightening can give false results. Ask your supplier for the recommended torque.
- Include a control. Fill the same formula in glass or in your current package so you can compare changes.
- Test enough units. Use enough samples at each condition and time point to spot a pattern, not a one-off.
Test conditions and time points
Most brands store samples under several conditions and check them at set time points. A common approach includes:
- Room temperature, as the baseline
- Elevated temperature, to speed up changes and flag problems early
- Cold or freeze-thaw cycles, which can affect seals and formula texture
- Upright, inverted and on-side storage, to check for leaks
- Light exposure, if the bottle is clear or the formula is light sensitive
Your lab or contract manufacturer will have its own protocol for temperatures and durations. Follow the protocol you use for stability testing and add the pump checks to each time point.
Testing pump performance
Pump performance tests are simple to run and tell you a lot. At each time point:
- Count how many strokes it takes to prime the pump.
- Weigh several doses and check that they are consistent and match the stated dosage. For example, APG's Infinity V2 Lotion Pump is rated at 1.5cc and the clip-lock all-plastic lotion pump at 3.5cc.
- Check that the actuator returns fully and at a steady speed.
- Note any change in the force needed to press the pump.
- Test the lock. An up-lock or clip-lock should still lock and unlock smoothly.
- Pump the bottle to near empty and check how much product is left behind.
For sprayers, also look at the spray pattern. A fine mist sprayer should still give an even mist. The Infinity HV Fine Mist Sprayer offers 0.5cc, 0.2cc and 0.19cc dosages, so check that the dose and pattern hold steady over time.
Reading the results
Compare each time point with the starting results and with the control. Look for trends, not single results. If a problem shows up, the cause is often one of these:
| What you see | Possible cause | Next step |
|---|---|---|
| Pump is slow to return or sticks | Formula too thick for the pump, or parts affected by the formula | Try a different pump style or dosage; ask supplier for options |
| Leaking at the neck | Torque, bottle finish mismatch or liner issue | Check torque and bottle finish tolerances |
| Weight loss over time | Evaporation through the seal or the bottle wall | Review seal and bottle material |
| Dose drifts | Wear or changes in seal parts | Share data with your supplier |
| Parts swell or discolor | Formula interaction with plastic | Discuss materials with your supplier |
How APG can help
APG can supply samples of its metal-free pumps and sprayers for your testing and talk through results with your team. Products often tested include:
- The Infinity Lotion Pump, with all-plastic components and no metal contact with the product.
- The Infinity V2 Lotion Pump, PP mono all-plastic with a 1.5cc dose.
- The all-plastic treatment pump for serums and thinner formulas.
- The Infinity HV Fine Mist Sprayer in three dosages.
- The Eternal Pump airless bottle, PP mono material.
See our metal-free pumps and sprayers for the full range. If you are planning a full changeover, read how to switch your products to metal-free pumps.
Common questions
How long should compatibility testing take?
It depends on your stability protocol. Many brands run tests over several months, with early checks at elevated temperature to flag issues sooner.
Can I rely on my supplier's test data?
It is a useful start, especially for similar formulas. Your own formula, bottle and fill still need their own test.
Do metal-free pumps need different tests than metal-spring pumps?
The tests are largely the same. Pay extra attention to return speed, actuation force and dose consistency over time.
What samples should I request?
Ask for the exact pump, neck finish, dosage and dip tube length you plan to use, and enough units to cover every test condition.
Should I test the full package for shipping?
Yes, if you sell online. Drop and leak tests on packed units catch problems that bench tests miss.
Ready to start testing? Request samples or a quote.