This will happen to you at some point in your career as a cosmetic chemist. You’ll either get a call from the QA people telling you a batch is “out of spec” or the huge batch you made for a consumer test is not right. Now, you have to figure out how to fix it.
How you do this depends on the type of formula but in this post we are going to focus on things you can do to save body wash and shampoo systems. We’ll cover other types of formulas in the future.
Note: sometimes a batch is just too far out of spec that you have to just dispose of it.
Common problems and possible solutions
1. Problem: pH is too high.
This can be solved by adding some type of acid to reduce the pH. Typically, something like Citric Acid or Lactic Acid works best.
2. Problem: pH is too low.
This common problem can usually be solved by adding a base like Sodium Hydroxide to increase the pH.
Note – You should always fix pH problems BEFORE trying to fix a viscosity problem! Sometimes fixing the pH problem will solve the viscosity problem.
3. Problem: Viscosity is too thin.
This is the most common problem you’ll have. The easiest way to fix most formulas is to put additional salt into the formula. As we’ve written about previously, salt will affect viscosity. Don’t add too much however, as that can push the solution to the other side of the salt curve and make it permanently thin. Another remedy is to add some additional secondary surfactant like Cocamidopropyl Betaine. This may change the micelle structure enough to make the batch thicker.
4. Problem: Viscosity is too thick.
This is another common problem for body washes and shampoos. Unfortunately, it’s a little tougher to fix. While salt addition could make it thinner, that is too difficult to control so it is not recommended. Better is to put in additional nonionic surfactant or a lipophilic ingredient. Diluting with water is another possibility but that will dilute all the ingredients in the formula and could lead to a lower quality product. One other option is to make a completely new batch but withhold the salt. Then blend the new batch with the old in the correct ratio to get the right viscosity.
5. Problem: Color is wrong.
This can happen for a number of reasons but often it is because the surfactant you are using is more yellow than normal. One solution is to add additional color to the batch. You can take a small sample of the batch and mix in the appropriate amount of color until it matches a standard. Then calculate the amount that should be added to the full batch and make the adjustment. If the color is completely off you can either discard the batch, get marketing to approve it, or blend off the batch in such small increments that it doesn’t spoil the color of future batches.
6. Problem: Odor is off.
Sometimes the surfactant or feature ingredients will smell slightly different and make the whole batch smell wrong. Adding more fragrance is one possible solution. Another trick is to blend the batch with an unfragranced one, then add back the original fragrance to bring it back to an acceptable level. Often, fragrance problem batches have to be discarded.
7. Problem: Appearance is grainy.
If you have a pearlized formula that is supposed to look elegant but it is grainy, one way to fix it is to heat the batch back up, mix it until it is clear, then rapidly cool it. This will make the particles reform in a better configuration and might solve the problem.
Remember that each formula is different and these solutions might not work for you particular system. However, these tricks have saved many a batch and they may just save yours too.
Do you have any tips on saving shampoo and body wash batches? Leave a comment below.