Every now and then a friend will inbox me asking a question about haircare, and usually it's a question that will be quite common. This is the first time I've posted a Q&A here on the blog but will continue to do so from now on when a question comes through that I find relevant and useful.

Q:  If I were to dye my hair blonde, how long should I wait before I go into a swimming pool? I don't want it to go green! This is a question with several implications, so let's break it down. Firstly, the length of time is really a minor factor. It's best to avoid it for a couple of days or until your first wash because of creeping oxidation, but we'll come to that in a moment, Before that, let's deal with why pool water can turn your hair green. You'll probably assume that it's chlorine that does that, but it's not. This is probably a false assumption based on the reasoning that chlorine gas is green, (itself named from the Greek khlōros, which refers to a pale yellow-green), but in actual fact it's copper ions in the water that get into your hair and take on the green hint when they are oxidised, (think of an old copper coin or the Statue of Liberty for examples of this). Creeping oxidation, as mentioned before, is when the oxidising agent used with bleach or dye, hydrogen peroxide, is not completely neutralised or rinsed out of the hair following a chemical process, although it's rare for this to last very long. However, if this does happen, it acts like a catalyst for the oxidation of the copper ions, causing your hair to turn slightly green. This is only really noticeable in blonde hair where there are fewer deep pigments to hide it, although it can cause red shades to look duller, or brown shades to look khaki. Additionally, the porosity of bleached hair allows residues such as metal ions from water to be trapped in the hair much more easily. So, what is the best way to prevent this? Well, the only answer I can give as a foolproof method is, of course, to wear a swimming cap. I can imagine you're grimacing. Yeah, they're not flattering and feel like they're trying to squeeze your brains out, but they keep the water off your hair and are the most effective way. The next best option - and I've been advising clients for years now to do this - is to use a leave-in conditioner before going in the water, which will help to seal the hair and keep it protected. But honestly, not just any product will do this. Mostly because as soon as you get your hair wet, the product dilutes and almost completely rinses out. But using one with the right ingredients can help a lot, so here are the three main things to look out for: 
A sequestering agent A what? Okay, a sequestering (or chelating) agent is a chemical that binds metal ions and renders them unreactive. They have been added to haircare products for years now - especially ones designed to prevent colour fade - to deal with the metal ions found in ordinary domestic water. The main family in question is EDTA (ethylenediaminetetraacetic acid), and the most common is Disodium EDTA. This is the easiest way to combat discolouration in treated water. 
Penetrative oils 
Your hair contains natural lipids but bleaching or over-processing can strip these and they tend to be lacking in porous hair, leaving the hair shaft gappy and susceptible to gathering residues and impurities. Replacing these lipids with oils can help to prevent other nasties from getting in but not all oils can penetrate into the hair in this way. Triglycerides are the best for doing this, which can be a pure active ingredient (such as capric or caprylic triglycerides), or as part of a pure oil such as coconut or sunflower oil. 
Hydrolysed proteins Hydrolysed proteins, especially keratin, have been making their way into more and more products as time goes on. The clinical proof that these have any real reparative effect on the hair is inconsistent, but there is reason to believe that with continued use they have at least a mild restructuring effect on hair. Aside from keratin, others to look out for are wheat, silk and soy. It goes without saying that a careful blend of penetrative lipids and proteins are the best way to attempt to strengthen damaged and porous hair. With all of this considered, I have dug up a product that I believe has the right balance of all of these things and would be an effective barrier to copper discolouration...
Ah yes, my trusty love of Sebastian! Potion 9 contains a blend of oils - olive, safflower, jojoba, babassu, rice and sesame oils - that will work together to both penetrate and coat the hair, plus hydrolysed wheat, soy and silk, and both Disodium EDTA and Tetrasoduim EDTA. These aside, the product is famed for being an effective nourishing and conditioning leave-in with added styling capabilities, so it's actually a great addition to your haircare arsenal, even outside of the swimming pool. Hopefully this will help you swimmers who have those burning questions about going blonde! Read more and find out where to get your hands on Sebastian goodies here: http://www.sebastianprofessional.com/en-UK/products/flow/potion-9