Cosmetic chemist's advice on beating batch-to-batch variation

Managing your quality control and batch-to-batch variability

Words by Amanda Foxon-Hill

While some batch-to-batch variation is to be expected with natural cosmetics, it is fair to say that most of your customers will become frustrated if their favourite moisturiser comes out of the packaging as a thick cream one purchase and then as a lotion the next.

As a manufacturer that works with many up-and-coming brands, we are frequently asked questions about product specifications. Some stockists even insist on products being supplied to them with Quality Control paperwork and this typically includes a product specification for the whole product and a Certificate of Analysis for each specific batch. This then begs the question ‘what are those things and how do I get them?’

The Product Specification

A good product specification should outline the main physical and/or microbial characteristics of your product so that whoever manufactures the product knows what they are aiming for and, importantly, what they are trying to avoid. Setting the specification for a product is a step-by-step process that involves all stake holders – the manufacturer, the brand owner and consideration for the final customers.

From a manufacturers perspective a broad specification is desirable as it is easier for them to hit a large target. Conversely, customers usually fall in love with an exact look, feel and colour and would, if they could, demand the exact same each time. The brand owner must deal with the consequences of both and manage expectations accordingly considering any constraints of their packaging, ingredient choices, brand promise and clientele. A pragmatic approach is best here so that the manufacturer avoids producing endless batches of stock that are then rejected (if the specification is far too narrow) while the brand owner and customers receive products that work and are consistent with the brand promise.

The exact parameters that make up a product specification vary across each product type and may include criteria that are specific to a certain brand or promise but in general, and as a minimum, product specifications typically include a description of how the product should look and smell, a measure of the range of acceptable viscosity, specific gravity and (maybe) refractive index and the product pH (if it contains water). Together these details paint a picture of the type of product being manufactured and supplied.

Getting a product into a position where a specification can be set is a process in itself. A product may have to be manufactured several times (batches) before a true specification can be created, one that is tight enough to be meaningful but broad enough to be practical in manufacturing. It is difficult to make a realistic specification on the first batch as one does not yet have experience of what is possible/probable with the product. Because of this it is typical for a product specification to be tweaked over its manufacturing life as knowledge of the peculiarities of that mixture and process become better known and understood. Changes to the specification may also be necessary if the final packaging that the product is sold in is changed.

In a nutshell, the product specification is an overview document that outlines the range of acceptable values for a product ensuring quality and uniformity to the level reasonably practical and commercially acceptable.

The Product Certificate of Analysis

While a specification is an overview, the Certificate of Analysis is a highly specific document outlining the actual test results of a batch. Each time a product is manufactured the batch will be measured against the specification. These measurements will determine if the product passes or fails the Quality Control check. If the product passes, a Certificate of Analysis will be written up for that batch and that batch will move on to become commercial. So, where a specification may outline a pH range for a product, the Certificate of Analysis will give an actual value for the batch.

So how does a brand go about getting this paperwork for their products?

As there are no legal minimum criteria for what should be on a specification or a Certificate of Analysis, a brand owner could create this paperwork themselves with minimal measurements based on what they see, feel and smell about their products. However, such lax specifications will be of limited value to the brand owner and their clients and will add very little to the overall professionalism of the brand. The best way to ensure your paperwork is relevant and meaningful is to have it produced in conjunction with a manufacturer who has an established and thorough Quality Control procedure in place and who is likely to be manufacturing your scaled-up product for at least three or more batches. This paperwork can then be used by the brand owner to help them satisfy themselves, their insurers, stockists and end users that their products are of good and consistent quality time after time, batch after batch and what brand wouldn’t want that?

This article was printed in the April issue of esprit Magazine.

Amanda Foxon-Hill – Cosmetic Chemist

Amanda’s diverse laboratory and factory experience spans a broad cross-section of the cosmetics industry from small-scale hobby manufacture all the way to 20 ton batch production. This hands-on expertise ensures that the formulation work produced by Realize Beauty on behalf of clients can be implemented on both a practical and commercially viable level.

Amanda is also a fun and vibrant presenter and has no difficulty in communicating sometimes complex scientific issues to the lay person or brand owner, thus allowing them to gain a deeper understanding of their brand or consumer product.

 

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