TRI Talks started on-line in 2020, with the aim of keeping healthy scientific discourse going through the COVID pandemic. Just like TED Talks, after which they were named, they set-out to be engaging, informative and thought provoking. Last year, 743 people from around the world registered to join the conversation. This year the TRI Talks will focus on Hair, Skin and Nail Science and Claims Methods, and will feature expert speakers from TRI. All four talks will be available to stream live and on playback. To join us, please register here for free.
TRI Princeton aims to achieve excellence in applied measurement science and to use this to improve human health, wellbeing and beauty through improved product design. This years’ TRI Talks, show that we are making good progress in this regard, as our scientists will present, for the first time, in three very different product categories, hair care, skin care and nail care. The agenda for the series runs as follows:
Advancements In Nail Care Claims Substantiation: Unveiling The Effects Of Cosmetic Treatments On Nail Properties Using Differential Scanning Calorimetry (Dsc) And Nail Flexer
Anyone who has swum in the sea or a salty swimming pool, has probably noticed the change in the feel and appearance of their hair afterwards. Hair can become dull or lackluster, as well as feeling heavy and tangling easily. However, on the positive side, having the beach hair look can be used by some as a fashion statement, providing fun, relaxed hair styles with strong curl definition. Beach hair effects, good and bad, are created from deposits of sodium chloride (NaCl) on the hair fibers, which changes their physical properties. This short article reveals how NaCl residues affect the hair fibers, and how scientists at TRI Princeton use advanced analytical techniques to quantify these changes.
Hair Friction: quantifying the degree of tangling within hair tresses
Tangled hair is a common complaint after swimming in saline water, and a combing force measurement allows for quantification of this change. Researchers at TRI Princeton showed that both medium brown virgin hair and 6% bleached hair required a significant increase in combing force after exposure to salty water, indicating increased friction between hair fibers that could lead to substantially increased risk of split-ends or fiber breakage. However, rinsing the hair with freshwater reduced the impact, while washing the tress with shampoo and conditioner restored the tress to the levels of the control sample, Figure 1.
Some people believe that treating their hair with oil before swimming can prevent or reduce the impact of NaCl upon tresses, as hair feels less tangled afterwards. To test this hypothesis, tresses were pre-treated with oil and then subjected to saltwater conditions. In both cases an increase in force required for brushing was observed when compared with virgin hair, but the use of oil led to a 78% reduction in combing force required when compared with untreated hair, Figure 2.
Does hair really look duller after going in the sea?
SEM imaging is an advanced technique that allows individual crystals of NaCl to be identified and the location of these crystals on the hair shaft. Using SEM imaging, no discernible differences between the quantity or location of NaCl coating on either virgin or bleached hair fibers could be identified, Figure 3. However, hair shine analysis revealed that salt residues led to a 22% reduction in shine.
Does saltwater exposure cause hair to be damaged more easily?
Thus far, NaCl has been shown to increase friction between hair fibers and reduce shine, which are both due to deposits of NaCl upon the hair fibers themselves. However, as well as these physical impacts upon hair fibers, there are also sub-microscopic impacts too, where the sodium and chloride ions change interactions between different chemical groups in the hair’s structure.
For example, exposure of bleached fibers to salt water caused the cross-sectional area of each hair fiber to increase by 3.2% and Young’s modulus to reduce by 12%. In terms of physical changes, the reduction in Young’s modulus shows that the bleached hair fibers become less stiff. In addition, the break stress (i.e. the stress required to break each hair fiber) for bleached hair changed from 214 MPa to 197 MPa, an 8% decrease. One possible explanation is that at a molecular level the NaCl is disrupting both hydrogen bonds and ionic bonds within hair fibers (by solvating any H-bond acceptors or ionic residues), reducing both the overall strength and rigidity of the hair, Figure 4.
That’s nice, but what do I need to do to keep my hair soft when I swim in the sea?
There are numerous take-home messages from this work, with the main one being that removing saline residues as soon as possible can prevent changes to hair structure at a chemical level and readily restores hair to its condition prior to exposure. Ideally, hair should be washed with shampoo and conditioner, but simply rinsing with fresh water can mitigate some of the physical impacts. If this is not possible, pre-treatment of hair with an oil-containing product seems to protect hair to some extent, particularly in relation to grooming and mechanical treatments.
What if I want the beach-look?
A variety of cosmetic salt-water sprays exist on the market that can simulate the effects of swimming in salty sea water. They don’t actually contain sea water, but just the sodium chloride that we have spoken about in this article. If used correctly these products do give good hair texture and curl definition and wash away very easily. However, as you would expect, the hair will feel gritty and rough.
How can TRI Princeton help me?
TRI Princeton provides a suite of analytical services that can measure the changes of a particular set of conditions upon the physical properties of the hair. For example, SEM can be used to visualize build-up of materials on the hair shaft, hair shine levels can be fully quantified and texture analysis can probe the smoothness of the hair fibers.
For further information in relation to how we can help, or to chat with one of our experts, please get in touch.
Many people say that their hair looks and feels different when they go on holiday or move to a different part of the world. This isn’t just their imagination, the hardness of the water coming out of your tap can affect your hair when you wash it. This short article explains how water hardness affects the hair, and how cosmetic products can help.
Water hardness usually refers to the amount of magnesium (Mg) or calcium (Ca) salts dissolved in water. Hard water contains high levels of Mg(II) and Ca(II) ions that can interact with the hair fibers and mainly collect on the cuticle (the hair fiber’s surface). In terms of the impact upon hair, the extent of metal ion uptake and the impact of these metal ions have both been studied.
The extent of uptake of Mg(II) and Ca(II) ions found in hard water are directly related to the condition of the hair, with both virgin and damaged hair (either through bleaching or chemical straightening) absorbing the metal ions, but damaged hair absorbing more overall. Regardless of the condition of the hair, more Ca(II) is absorbed than Mg(II). Water’s pH also has an impact, with higher water pH (more alkaline) leading to a great uptake of metal ions.
It might be expected that the build-up of lime scale crystals on the surface of the hair, in hard water areas would cause an increase in surface friction, and some laboratories have reported this. However, work by Evans et al suggests that hard water might reduce hair tangling by increasing hair stiffness and alignment. Again, more work needs to be done in this area to figure-out what is going on.
The science part
The propensity of damaged hair to absorb more metal ions, and therefore be affected by these ions, is likely due to the chemical entities present within the hair fiber itself, Figure 1a. Damaged hair contains more carboxylate and sulfonate groups (present as cysteic acid) due to oxidative cleavage of peptide bonds and disulfide bridges, respectively, during treatment with peroxide, Figure 1b, and can readily make a strong bonds to both Mg(II) and Ca(II) ions. The preference for bonding to Ca(II) rather than Mg(II) is likely due to the energy required; Ca(II) has a larger ionic radius than Mg(II) (as it is further down Group 2 of the periodic table) so the forces between the metal ion and surrounding water molecules will be smaller, so the hydration sphere will be removed more easily allowing the carbonate and sulfonate groups to coordinate instead of water.
The impact of pH is also related to the presence of carboxylate and sulfonate groups, Figure 1c. A lower pH leads to an increase in protons (H+) in solution, meaning the carboxylic acid and sulfonic acid residues will be protonated. This reduces their potency for binding to the metal ions because they are no longer anionic (negatively charged). Washing or treating hair at higher pH increases the levels of Mg(II) and Ca(II) ions present in the hair because the carboxylate and sulfonate groups are deprotonated, so can readily bind to the metal ions.
That’s nice, but what do I need to do to keep my hair soft when washing in hard water?
When washing hair in hard water, the key is to protonate the anionic (negatively charged) residues through use of an acidic shampoo and/or conditioner, or the use of a chelating agent that sequesters Mg(II) or Ca(II) ions. The product should ideally have pH <6. This will ensure that any metal ions are less likely to interact with the hair, and hair should be less affected.