Formulators Can Avoid Quality Disasters

Formulators all know that the true reason for the success of any product is the formula. Yes,  package designers all think it is the package that the consumer really wants, marketing thinks they can sell anything in a bottle with their masterful wordsmithing and the finance people think it is all about the right fiscal management—but formulators know that the product's formula is the thing. Reality, of course, is that every piece of a product's creation is important to its success.

Focusing for a moment on the formula part of a product’s success, there are a number of things that cosmetic chemists can do to avoid problems in production and ultimately in the marketplace. In the laboratory, almost anything is possible. Ingredients can be heated quickly to the temperature desired, cooled just as quickly, blended ever so gently or homogenized with almost unlimited time and energy—and all of these things can be done however the formulator wants.

Production life however is very different, and a formulator that takes those differences into account during formulation will keep production problems to a minimum. The time it takes to do everything is usually a lot longer. Batches take longer to heat and cool–hours longer. Mixing a thousand kilos of anything is not the same as mixing one kilo. Transferring the product once it is made is also very different in production than in the lab in many cases. The best formulations are the ones that can be made successfully both in the lab and in large quantities.

Temperature changes can take a long time. The few minutes spent in the lab to heat a phase to 75°C will often take an hour or more in production. The larger the batch, the longer time it takes to achieve the target temperature. Similarly, once a batch is put together at an elevated temperature it will take a while to cool. If there are temperature sensitive ingredients in the formula, they will spend hours being quite warm.

If a formulation requires homogenizing in the lab for a half an hour, it will require huge amounts of time to achieve the same result when a large batch is made in production. Although homogenizers in production are larger than the ones in the lab, they are usually not sufficiently larger to be proportional to the change in the size of the batch. Ten minutes of homogenizing for one kilo scales up to 1,000 minutes for a 100 kilos. That is over 16 and a half hours. A thousand kilos would require 10,000 minutes or almost seven days. Even if a homogenizer that is five times bigger is used, homogenization for 2000 minutes or almost a day and a half will be needed to achieve the same results.

Conversely, if a formulation cannot tolerate any mixing or shear once it is made, problems will be encountered during production. Moving product out of a mixing tank into a storage container or drum and then into a filling machine involves pumping. Pumps all inflict some amount of shear on the product. If a product cannot tolerate additional shearing, the formulator should be aware of it and make it clear to production when they start to make it.

At the formulation end, it is a good idea to think about large-scale production from the beginning, and develop the premix phases and batching procedures to take these things into account. 

Another important part of the lab to production transfer process involves product specifications. The measurements of pH, viscosity, specific gravity, refractive index, and the like are the basis for the quality control specifications that will be used to determine if the product has been made correctly or not. The formulator needs to write specification ranges for the various parameters so that they are meaningful. This almost sounds basic and simple, but it doesn’t always work out that way. The production quality control (QC) lab will often generate their own specification ranges based on data that comes out of the first few pilot or production batches. The ranges they determine do not always make sense though. If they apply statistical treatments of the variation in readings that they see, and want to allow several standard deviations around the average reading that they get, the ranges can become absurdly broad.

For instance, suppose the specific gravity of a product made in the lab is 1.00 gm/ml. If the variation in the first few batches ranges from 0.990 to 1.010 gm/ml, these are readings that reflect reality. If a specification range is set wider than this, product made outside the original range will have problems. Tentative specification ranges are often set fairly wide so that out-of-spec readings are avoided. On the low end, this can allow aerated product to proceed into filling. The texture of the product can suffer, and in some cases, it becomes impossible to fill the correct amount of product into the package to satisfy the net contents claim on the label. When the air settles out of the product as it stands, the number of ml of product in the package could fall below the label claim.

On the high end, an emulsion that should have a specific gravity of 0.990 to 1.010 gm/ml cannot have a specific gravity of 1.02 gm/ml. If the product is that dense, there is something seriously wrong with it. Formulators know that you cannog take the ingredients for a lotion and make it more dense than what the formula intrinsically can achieve. The only way for the specific gravity to be too high is for there to be things in the batch that do not belong there. The QCl specifications are supposed to identify those problems and prevent them from being released. When production is more concerned about avoiding out-of-spec situations than the specification ranges provided, the product will suffer.

When the QC tests show readings at either end of each of the specification ranges, it is supposed to mean that the product is acceptable. If the specification ranges allow readings that indicate that the product is in fact substandard, then the purpose of QC and quality assurance is being thwarted. Absurd specification ranges are usually motivated by the desire to avoid rejections rather than protecting product quality. This cannot be allowed to happen.

The cosmetic chemist and the formulator can make sure their creation is as successful as possible by keeping manufacturing in mind throughout the process. Make sure the formulation is makeable. Make sure your specifications protect the real quality of the product. Assuming that other people in the production supply chain will figure all this out correctly can be a costly mistake.

More in Methods/Tools