Dear Valerie: I listened to a recent episode of The Beauty Brains podcast where you mentioned you have a special technique for covering up your beaker to minimize water loss. I can’t ever seem to lose less than 10% water in my batches. What’s your secret? —H2 LOW
Dear H2:
I appreciate that you’re measuring the water loss content of your batches. I recently assisted a manufacturer in a tech transfer of a hot pour formulation, where I suspected the formulating chemist lost a considerable amount of water in the hot pour and did not QS any back to the batch. When I queried the formulating chemist, I discovered he, in fact, did not measure water loss and I was advised I would be fine if I “just covered” my beaker. I’m not sure in what world 22% water loss is considered fine (which is what the product lost), but it’s certainly not replicable in production and puts the product into a regulatory conundrum with the product’s preservative now being over the legal limit.
When I ran R&D for a leading salon brand, I was pretty militant about the chemists measuring, understanding and correcting water loss as a critical part of their lab work. Indeed, it is a very good practice to engage in if you’re not doing it. If you sometimes lose 10%, or sometimes 15%, but then in production only lose 5%, the performance and specifications of your product can be quite different from batch to batch. Measuring the yield of each batch will help you understand what is typical in the lab vs production, ensure you’re consistently producing products and know whether to QS your loss back.
If you aren’t sure what an acceptable level of water loss is for your product, I recommend connecting with your manufacturing team to understand what the typical yield is for varying products in certain manufacturing tanks. They can advise what water loss quantity is typical, which will guide you in your lab work. For example, if a shampoo typically loses 3% water in Tank 12, you know that [in the lab] your ideal target is 97% yield, and you should never QS beyond that. If they’re not measuring yield, we have a different problem.
In my lab, I would see most chemists cover a beaker by taking a square piece of aluminum foil, cut a slit down the center (being careful not to cut it all the way through), then slide the slit around the mixing shaft. Smash it down around the sides of the beaker, and you’re good to go! The problem with this technique (aside from the fact a small piece of aluminum usually rubs against the mixing shaft and makes a horrible screeching sound) is that there is often a gap around the mixing shaft, or the slit is not closed all the way, or both. To top it off, as you add ingredients and peel the foil back, the foil cover breaks or the gaps get bigger, allowing for more water evaporation. On a lab scale, this increase in water loss is too much for a batch. On average, I bet anyone using this method is losing at least 10% water.
I’ll end my diatribe against non-yield measurers and sloppy beaker covers, climb off my soapbox and let you in on my secret to reducing water loss on the bench!
The trick I use is to cut three small rectangles of a hearty, thick aluminum foil that is not subject to easily tearing. (When I’m feeling bold, or I don’t have any foil, I use three rectangular pieces of plastic cling wrap.) Place one rectangle firmly on the backside of the beaker, away from you. Place the second rectangle perpendicular to the first piece, on the right or left side of the beaker. This leaves a small triangle open, which the third rectangular piece is placed diagonally over. This is the only piece that gets touched or moved during the whole batching process, when adding ingredients or checking the batch. If a small gap does develop, I keep aluminums scraps on hand and cover the hole up.
Aside from ingredient additions, I don’t remove any coverings until the batch begins the cooling process and reaches 60ºC. Only then do I peel back the layers, do any stirring that needs to be done and strategically replace the covers. I fully remove everything when the batch reaches 45-50ºC and go wild with whatever I need to do.
With this method, I lose (on average) 5% water or less. It seems simple, and obvious, but you would be surprised how this little improvement works to produce more consistent, realistic outcomes on par with an average production.
I’ve converted many people to this method and—if you’re still rolling your eyes but are still reading! —can provide references to the believers of this technique, should you remain skeptical. (November 2023)
Happi’s Dear Valerie column appears in Happi’s print magazine. You can access the digital issue here.
Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com. Do you have a question for Valerie? Ask her here:[emailprotected].
