First, I am convinced that no product is going to "repair" your hair. If it is damaged, the only thing left is to get a haircut. But I do believe that chemicals can improve the situation of your hair, parts that are not too damaged or dead yet.
So, I have been using this masque, twice a week for exactly one month. I changed my whole hair routine and stuff, but so far I have no split ends and my hair is very soft, shiny and looks healthy. It is important to mention, that I do not iron, blow-dry, or dye my hair anymore.
It smells very nice, sort of apple scent. Anyway, it is true that you have to use more product than the bottle claims to be needed (And I have short hair, maybe an inch under my shoulders) and it absorbs real quickly, which sometimes, makes you use more product. I leave it in for 4 o 5 minutes.
I always use a comb to distribute the product all over my hair, and never apply it over the level of my ears (Tyra Banks' rule). I haven't had any issues with the masque, tough it is expensive, it is so far the best treatment I have tried.
It is very important that you rinse the masque (and not only the masque, but every conditioner) with cold water, or lukewarm water. If it is warm, it will not rinse as it is supposed to be, so it shall leave residuals and that can weight down your hair.

It's horrible!
At least on my fine, treated, coarsed hair.
Weight them down hair, looking dull, without any added shine, without any force, vitality... OMG really disappointing for the price they sell it!!
Wouldn't reccomend. Will not buy it again. Forget it!

I did not find this masque as horrible as most reviewers below me. Actually, I liked it. Over the past 3 weeks I have changed my hair color from near black to midtone golden blond. It took two bleachings and 3 dyejobs (bleach + color, after a week another bleach + color, week and a half later another color to get the color perfect) to get it right. In my opinion that was not so bad, normally it could take a lot more bleachings. But needless to say both my own hair (which was dyed darker) and my extensions (which were naturally dark) did not love me very much.

I bribed my hair into loving me again with this mask (along with other products), which worked. My hair feels stronger after every time I use it and I do not feel the need to use a mask every time I wash my hair, which is once every 2/3 days. I do not think this mask is fully responsible for the good state of my hair, but it has played its role. However, I will probably not purchase it again. The reason for this is that I have to leave it on for at least 45 minutes to get the best results, and that I have to use way too much. I mean A LOT. I have a lot of hair on my own and my extensions are buttlength, so yes, that is a lot of hair. But still. Four uses out of one tub? Hell no. If I want fast results, I will stick to the Joico Hydrator. If I'm in a mood where I don't mind the hassle, Redken CAT + 30 mins Macadamia mask provide the best results. I will finish this tub gladly, and if I can find it in a sale I will purchase it again, but otherwise I will continue with my stash.

I am a hairstylist who has worked with Kerastase for 3 years. The reason this product gets bad reviews is because it is actually possible to over proteinize your hair!

Most people think their hair is damaged, when in fact it is dry (which is why masquintense gets such great reviews). I never use this product with the whole force architecte line. And I never use it frequently. And I never leave it on long. The sign of over proteinized is a brittle feel! Basically this masque works too well! So I use this masque once every one or two weeks, in conjunction with the kerastase moisturizing or color treated line, and it works great! (btw, I have highlighted blonde hair from a natural very dark brown, so I know about damage)

Dont waste your money on this conditioner its awful!!! I bought it full price for £26 and i felt like crying when i used it. When you first put it on you expect it to feel like a conditioner a little bit moisturising, it doesnt" After leaving it on for about 15 mins i rinsed it out and my hair was tangled and felt coated in a horrible waxy substance. I then blow dried and it was soooo knotty and dry! I gave it a chance and used it for about a month and needed a trim it was that bad. Try masque intense instead that one works wonders.

The worst that could be with my hair for the price!
Never use it for non-dyed hair!

Completely disappointed with this hair mask. I mean, it didn't make my hair horrible but it didn't improve it either.
It is very expensive and doesn't really do much for the hair, it works just as any other hair mask you can get in your local chemist for 1/3 of the price, so it is really NOT worth it.
If you want an inexpensive hair treatment that will actually help repair your damaged hair try the egg bomb, which will put more protein into your hair than any other mask! :)

I don't know why my experience is so difference from everyone else's, but my hair came out so smooth, so insanely shiny, with tons of movement, even better than with the Masquintense (but it could have been a cumulative effect with Masquintense).
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I permed my frizzy, poofy, thick Asian hair a little less than a week ago. When I came out of the salon, my hair was rough and breaking badly. I used Masquintense with my first two washes in an effort to recuperate, and the results were miraculous. I didn't think my damaged hair would be able to even better. But I had a sample of this masque (contains 15mL) and thought I might as well try it.
I applied it the same way I do my Masquintense. I squeezed every drop out of my sample pack into a little 50mL spray bottle, filled the bottle 80% full with water, and sprayed the whole thing into sections of my hair while massaging it in. It was much thinner in consistency compared to Masquintense, looked more like a conditioner, which had me worried. I left it on for about 20mins (had time restraints), rinsed it off. I applied my usual leave ins and blew dry.
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Like I said before, although hair has a little less volume, it was so smooth, had tons more movement and was amazingly glossy. I never knew my recently permed hair could be so soft, smooth, and shiny. Perhaps others didn't like it because they applied it differently, or wasn't using it in rotation with Masquintense?
I highly recommend this as an extra booster for people with chemically treated hair already using Masquintense (since others seem to have only been using this masque).

This is the worst thing I've ever done to my hair. I bleach a lot, so I thought I'd try this product when my mum got a sample for free (I'm so glad I didn't buy this!) but it was a big big mistake. I used it after I bleached, so it was pretty dry hair, and left it on all night which I sometimes do with conditioner. To my horror when I woke up and washed it off my hair was in worse condition than before! ALL of my hair was dry brittle and looked like straw, even on the bits that didn't get touched by the bleach. This made my hair worse. Never ever use this.

It was recommended by the Kerastase salon by my house that I use this as part of a ritual with Bain Force Architecte shampoo, Ciment Thermique heat protectant leave-in milk and Fibre Architecte reconstructive serum. You see, I am trying to grow out my wild, frizzy, colored, heat damaged hair. It is thick with terrible split ends from all the heat and having lived in Hawaii. This masque was supposed to be the moisturizing savior of my hair, and while I thought the Kerastase Resistance system as a whole was better than anything from Sephora, this masque is not the best from Kerastase. The nicest thing about this product is the fragrance. I tried Masquintense and there is no comparison. Though Masquintense just smells like a very strong scented lotion / soap, its results are much, much better! Even after using a whole bunch of Masque Force Architecte, and the rest of the system mentioned above, my hair still feels brittle & breaks, whereas Masquintense delivers long lasting moisture & much healthier hair overall through till my next wash. I am now only using up my MFA just to get thru it because I paid so much for it. I can't wait to be able to finish this tub so I can use only Masquintense.