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What is Batching?

In earlier posts, I've mentioned making laboratory batches, pilot batches, and full-scale trial and manufacturing batches. Today, I'd like to break down what that actually means. Hopefully, you will find it to be quite simple and similar to a process you are already familiar with - cooking at home in your kitchen.

Laboratory Scale

If you're making a batch of a cosmetic product in a laboratory, you'll probably refer to that as working in the lab, making a batch, creating prototypes, or performing laboratory experiments. What does this all mean? Basically, you are planning to be working at a bench making a batch in the approximately 500 gram to one kilogram scale. I've included a photo of a typical laboratory bench below. If you spent time in a high school chemistry class, it probably looks quite familiar.

A typical laboratory bench

When you're making a batch of a product as a process engineer, typically the formula will be finalized but the process will be what you are testing. For simplicity, let's assume this batch is just seeking to replicate the work of the cosmetic chemist who created the formula. Ideally, they will have a great summary in their laboratory notebook of exactly what they did including an equipment list, raw material list with quantities and vendor lot numbers, and mixing and temperature settings. If you're a home cook, that list probably sounds very familiar to any recipe you've used in the past. The next steps are also similar to cooking!

First, you should check your raw material supplies for all the materials needed. There is nothing worse than getting to the end of your batch and realizing you don't have enough of the final ingredient! So, the first step is to gather all the ingredients and check the quantities, expiration dates, and safety ratings to determine any personal protective equipment (PPE) requirements. The nice thing about personal care laboratory work is that most ingredients are quite safe. Generally, you will only need safety googles, gloves, a lab coat and potentially a respirator for the addition of any fine powders.

Laboratory station prepped for batching

Next is a matter of personal preference. Some folks like to weigh all raw materials out ahead of time and just dump and mix once they get into the swing of things, similar to mise en place for a chef. This is probably easiest for a formula like a hot melt where you add most ingredients at the start of the recipe and heat and mix. For more complicated formulas with many raw materials, it is probably easier to weigh things as you go along to avoid the confusion and mess of a bunch of weigh boats sitting on the bench. Either way, you will be spending a good amount of quality time with a scale, plastic weigh boat, spatula or tongue depressor as you get ingredients weighed out in the correct quantities.

Scale, weigh boat, and raw material in the foreground. Mixing batch in cooling water bath in the background.

Next is the fun part! Adding those raw materials into the beaker in the optimal order, mixing at the optimal temperature and mixing speed for the right amount of time. If you're early in the scale-up process, it's up to you to decide what those "optimal" settings are. For the first batch, you'll likely follow the same settings used by the formulator. In general, the goal of the process engineer is to make the process is simple as possible and keep temperature and mixer settings as low as required as discussed in the Process Engineer post.

During the batching work, it is very important to keep notes in your laboratory notebook of everything that happens, good and bad. I personally like to enter the list of raw materials in formula and the detailed step-by-step recipe into Excel. Before I make my batch, I print out copies and tape them into my laboratory notebook. During the batch, I fill in times, temperatures, mixer settings and notes as I work through the process. I find that this format helps keep everything looking neat and saves me time rewriting information by hand as I make multiple iterations of the same formula.

The final and not very fun step is clean up! Much like a home cook, you will ideally finish the process with a great looking final product and a terrible looking bench. It's important to clean equipment, wipe down surfaces, and put everything away both to respect others in the laboratory and to make sure the space is safe and free from messes or unlabeled chemicals.

Pilot Scale

The steps for the pilot scale are very similar to the laboratory scale. You will most likely be working in a research and development space and have the autonomy to adjust speeds and temperatures on the fly if needed. The major differences will be the scale and the number of people involved. In the lab, it was likely just you on your own making about one kilogram of material. At the pilot scale, you'll be making a much larger batch in the range of 20 to 500 kilograms. You will also potentially have a larger team. The pilot plant may have a dedicated team at the contract manufacturer or in a larger company. At a smaller operation, you may be running this experiment on your own.

In terms of batch preparation, the pilot staff may do this work for you. This prep work may include the pre-weigh of raw materials, preparation of equipment, batch paperwork, and even cleanup after the batch if you're lucky! The role of the formulator and/or process engineer in this instance is to monitor the batch, take lots of notes on any observations, and address in real time any unexpected differences or issues that arise that were not noted as part of the laboratory scale.

Pilot kettle example

The pilot scale batch will likely be made in a good manufacturing practices (GMP) environment with tighter controls than the research and development laboratory, more paperwork, and more personal protective equipment (PPE) like hair nets and steel toe boots. These batches are commonly used for applications that require more robust control like safety testing, human-use studies, or other clinical testing. The size of the pilot batch is commonly dictated by the number of samples required for stability testing and various other tests and is measured in scale of buckets instead of beakers or small glass jars.

Product made at pilot scale

Full Scale / Manufacturing Scale

The final batch type is the size that will be used for commercial production. In this case, the individual batch made is still referred to as a batch, but you've left the laboratory or pilot plant and are now in the manufacturing area. The department making the batch is commonly referred to as Compounding.

The manufacturing scale process will be very similar to the pilot scale. The main differences will be the controls in place and the people involved. In order to make a formula on the manufacturing floor, there will be a variety of documents and paperwork required like the final recipe or batch card, the final product specification, and work instructions for both the batching and the post-batch cleaning procedure.

There are also several groups involved. Most companies have an entire department devoted to pre-weighing raw materials. Warehouse staff will stage the materials at the manufacturing kettle prior to batching. The Compounder will make the batch alone or with a partner during normal operations. During the scale-up process for a new launch, the process engineer will be on hand to monitor the entire manufacturing process and troubleshoot any issues that arise.

How big is this scale? It varies. I've personally worked on kettles ranging from 500 kg to 21,500 kg. The 500 kg kettle was on wheels and could be rolled around by one (strong) person. The 21,500 kg kettle was two stories tall and about 10 feet in diameter.

Overall, I hope today's post helped you understand exactly what is meant by the different types of batches made during new product development and what is done at each size. If you have any questions, please let me know in the comments below!

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