What Happens During a Pilot Batch Production Run? A Buyer's Guide

Why a pilot batch exists and how it differs from a lab sample

The lab sample you approved was made by a chemist in a beaker or a small mixer, weighed by hand, heated on a hot plate and stirred until it looked right. The commercial batch will be made in a jacketed tank with a mechanical mixer, heated and cooled by a system with its own rates, and filled by a machine that behaves differently with every viscosity. A pilot batch is the step in between: a scaled-up batch, typically produced on production equipment or a smaller version of it, to confirm that the formula behaves the same way when the process changes.

The differences that matter between the two:

• **Mixing energy:** a large tank shears the product differently from a lab mixer, which can change viscosity, emulsion stability and the way pigments or actives disperse.
• **Heating and cooling rates:** a tank takes longer to heat and cool, which can affect emulsions, waxes and heat-sensitive ingredients.
• **Order and timing of additions:** steps that take seconds in the lab take minutes at scale, and some ingredients are sensitive to that.
• **Filling:** the real filling line reveals whether the product flows, foams, strings or settles in a way that affects fill accuracy and appearance.

In beauty and cosmetics manufacturing, the pilot run is where a formula that looked perfect at 500 grams either confirms its behaviour at scale or reveals a gap. The same logic applies in supplement manufacturing, where blend uniformity and flow in capsule or sachet filling are tested at pilot scale. The point is not to find out whether the product is good; you decided that at sample approval. The point is to find out whether the process can make it reliably.

Stage 1: Pre-pilot preparation and what you should confirm

A pilot run is only useful if what goes into it matches what will go into full production. Before the batch is made, the factory prepares a batch manufacturing record, confirms raw material lots, and sets up the equipment. This preparation stage is where the buyer has the most leverage, because the decisions taken here determine what the pilot actually tests.

Confirm these points with the factory in writing before the pilot is scheduled:

• The formula version. It must be the final approved version, including any adjustments made after the last sample round.
• Raw material sources. If the pilot uses a different grade or supplier of a key ingredient than the commercial batch will, the pilot proves little. Ask for the raw material specifications and whether the same lots or equivalent lots will be used.
• The equipment. Will the pilot be made on the actual production tank and filling line, or on dedicated pilot equipment? Both are acceptable, but you need to know which, because the second option leaves some scale-up risk for the first commercial batch.
• The packaging components. The pilot should be filled into the real primary packaging, not lab jars, so that compatibility and fill behaviour are observed.
• The tests to be performed and the acceptance criteria. Agree the list and the limits now, not after the results come back.

This is also the moment to settle who attends. Some buyers visit for the pilot run; others ask for a video record and the completed batch record. If you are managing global sourcing across several factories, a consistent pre-pilot checklist is the simplest way to compare how different suppliers prepare, and it reveals a great deal about their discipline before any product is made.

Stage 2: Manufacturing the batch, step by step

On the day, the factory follows the batch manufacturing record, which is a written sequence of every step with the quantities, temperatures, times and equipment settings. For an emulsion such as a cream or lotion, the sequence usually looks like this:

• Water phase ingredients are weighed and dispersed in the main tank, then heated to the target temperature.
• Oil phase ingredients are weighed and melted in a separate vessel to the same temperature.
• One phase is added to the other under controlled mixing to form the emulsion, with homogenisation if the formula requires it.
• The batch is cooled under mixing at a controlled rate, and heat-sensitive ingredients such as fragrance, preservatives and some actives are added below a set temperature.
• The batch is checked for appearance, pH and viscosity, adjusted if the record allows, and held for release testing.

For anhydrous products such as balms and oils, the sequence is simpler but temperature control still matters, which is why a herbal product OEM run often focuses on melt uniformity, cooling and the point at which essential oils are added.

What the factory operators record during this stage: actual weights against target, actual temperatures and times, mixer speeds, observations such as foaming or clumping, and any deviation from the record with the reason. This document is the most valuable output of the pilot after the product itself. Ask to receive a copy. A factory that resists sharing the batch record, or whose record is a few handwritten lines, is telling you something about how the commercial batch will be documented.

Stage 3: In-process checks and release testing

Testing on a pilot batch happens in two layers. In-process checks are done while the batch is being made, to confirm that it is on track. Release testing is done on the finished batch to confirm it meets the agreed specification before anyone decides it is acceptable.

In-process checks typically include appearance, temperature at key steps, pH after cooling, and viscosity once the product has stabilised. Release testing goes further and, depending on the product type, may include:

• Physical and chemical parameters: pH, viscosity, density, colour and odour against the standard.
• Microbiological testing: total viable count and absence of specified organisms, where the product type requires it.
• Preservative efficacy, usually on the first batches of a new formula, to confirm the preservation system works at scale.
• Fill weight or volume checks on packaged units.
• Packaging checks: leakage, torque on caps, pump function, label adhesion and print quality.

The pilot is also when stability and compatibility studies on scaled-up product usually begin, if they were not already started on the lab sample. Ask the factory whether stability will be run on the pilot batch and how the results will be communicated.

As a buyer, you do not need to interpret every laboratory result yourself, but you do need to see them. Request a certificate of analysis for the pilot batch, with the specification limits next to the results, and keep it with the batch record. If any result is out of specification, ask for the investigation and the proposed correction in writing before agreeing to proceed.

Stage 4: Evaluating the pilot and deciding what to change

With the batch made and tested, the evaluation begins. This is a joint exercise between you and the factory, and it works best when both sides compare the pilot against the approved sample using the same criteria.

A practical evaluation checklist:

• **Sensory comparison:** place the pilot next to the retained approved sample and compare colour, odour, texture, spreadability and absorption. Involve more than one person and record observations.
• **Behaviour in packaging:** does the product dispense correctly from the pump or tube, does it settle or separate in the bottle, does it look right through clear packaging?
• **Fill accuracy and appearance:** are fill levels consistent, are there air pockets, is the product cleanly filled without residue on the neck?
• **Process observations:** did the batch record show any deviation, difficulty or adjustment? These are early warnings for the commercial batch.
• **Test results:** do all release results sit within specification, and are they close to the lab sample values?

Three possible outcomes follow. First, the pilot matches the sample and the process ran cleanly, and you approve it as the reference standard for production. Second, minor differences appear, such as slightly lower viscosity, and the factory proposes a process or formula adjustment, in which case a second pilot or a documented adjustment may be needed depending on the size of the change. Third, a significant issue appears, such as instability or a packaging incompatibility, and the project returns to development.

Resist the temptation to accept a pilot that is almost right on the assumption that the commercial batch will be better. Scale-up tends to amplify small differences, not remove them. The pilot that you approve becomes the retained reference against which every future batch is judged, so it should be the product you actually want.

Stage 5: From pilot to commercial batch, and what to keep on file

Once the pilot is approved, the factory finalises the master batch record, locks the specification, and schedules the commercial run. Your work as a buyer shifts from evaluation to documentation, because the records created around the pilot are what protect you when questions arise later, whether from a regulator, a distributor or your own quality review.

Keep the following on file for every pilot:

• The approved formula version and the final specification with acceptance limits.
• The completed pilot batch record, including any deviations and their resolution.
• The certificate of analysis for the pilot batch.
• Retained samples of the pilot, stored under the conditions the factory recommends, with the date and batch number.
• Photographs or video of the batch in its final packaging.
• Written approval from your side, naming the pilot as the reference standard.

Agree with the factory how the commercial batch will be compared against the pilot. Many buyers ask for a pre-shipment sample from the first commercial batch to be compared with the retained pilot before release, and for the certificate of analysis to be shared before goods leave the factory. If your order is at the standard MOQ of 1,000 units per SKU, this comparison step is small effort relative to the cost of a batch that does not match.

Finally, treat the pilot run as part of supplier verification, not just product development. How a factory plans the pilot, documents it, tests it and discusses the results tells you more about its real operating standard than any certificate on the wall. A well-run pilot is strong evidence that the factory can repeat the product; a poorly documented one is a reason to ask harder questions before committing to volume.