The science behind the Yellow Jersey with CASTELLI [Interview]
Somewhere in the middle of Norway lies a place called Romsdalen.
For some, it’s just another spot on the map – but for others, it’s a legendary hub for climbing – an iconic destination for world-class skiing and mountaineering – and the training ground for some of the best trail runners on the planet, including Kilian Jornet.
Each year, in this stunning landscape, the Romsdal Academy takes place – a one-of-a-kind festival celebrating the spirit of mountaineering – supported by Houdini Sportswear.
The transition between spring and summer is a magical time in Norway’s coastal mountain range – and for lovers of mountain sports, it’s nothing short of paradise.
The idea behind Romsdal Academy is to elevate your mountain skills while having an unforgettable time. This four-day event is packed with activities, workshops, learning opportunities, new friendships, and breathtaking outdoor experiences – from steep skiing and avalanche/improvised rescue training to sport climbing, peak scrambling, and mountain running – there’s something for everyone.
It’s a rare chance to truly connect with nature and be fully present in the moment. We had the opportunity to experience this incredible gathering and sat down with Eva Karlsson – CCO of Houdini Sportswear – to talk about how we ended up there, the history of the Academy and the region, the importance of being out in nature during turbulent times – and what we can all do to help protect it.
Our interview follows.
In terms of the small details, we asked if it would be possible to introduce an element of the hexagon. France is always represented by that hexagon shape, and it had never been used before in the Tour de France. We wanted to introduce it, so you can see it here on the zip and also on the patch, bringing that hexagon shape into the race.
For me personally, this logo is very familiar because when I started working in cycling in the ’90s, it was very prominent. It was huge on the chest. Back then, it was huge on the chest, but over time it got smaller and smaller. We wanted to make it quite prominent again because it’s very important.
With the elastics, I wanted to add a little detail. You want to add details so that if you win a jersey, you can take it home, put it on your bed and think, “Wow, this is crazy.”
We also wanted to introduce a product that doesn’t exist in the Castelli collection: an aerodynamic long-sleeve jersey for the riders. This is what you’ll see on all the mannequins at all the races.
For me, it was really important to bring that technical element to the jersey. The sleeve fabric is one of the most expensive fabrics in all of Castelli.
We tested around 12 different versions, looking at the spacing between the ribs and how high they stood off the sleeve, to find the fastest version. This version is actually the fastest at race speeds.
There’s another version used by our sprinters, Tim Merlier and Paul Magnier, because they reach higher speeds – 60 km/h and above. They have a different fabric, but nobody sees that. People just think it’s the same ribbed fabric, when in fact riders on the team are wearing different versions.
Usually, there’s no double zip on the race jersey. Jackets and other products, yes, but not the race jersey.
Another small detail is the French flag on the zip. This is only for the yellow jersey.
What they really wanted to do was address the heat. If you look at the Tour this year, temperatures were over 40 degrees and the riders were roasting. So we partnered with Polartec. This is Polartec Power Dry.
[Is this something new, or is it already on the market?]
It’s not on the market yet. It’ll be raced for the first time at the Tour de France. It’s not available in our collection in this form, so the riders of Soudal Quick-Step and the Tour de France winner will wear this jersey next year.
We also made a speed-suit version. You have the bib shorts, with the ultralight top, and you still maintain all the aerodynamics of the sleeve.
Polartec were on a call with us. They had a big board meeting last week, and I told them their fabric would be used in the yellow jersey at the Tour de France.
They got pretty emotional. They were like, “Oh my God, this is the pinnacle of the sport.” For them, seeing Pogačar and these guys in Polartec Power Dry fabric is amazing.
[That’s more for breathability, not a cooling fabric?]
No, it does have cooling properties. They’re activated by sweat and the heat of the body.
[This is only for summer, for hot weather? They’ll have an option to choose?]
Between the normal aero and the ultralight versions – three options for every kind of weather. They can have the long-sleeve aero, the normal aero or the ultralight aero, and they’re all available as suits as well, with the shorts and the top.
The last one is the podium jersey.
When you see it on TV, you might think it isn’t very technical, that it’s just a T-shirt they put on to go onto the podium.
But it’s actually highly technical because we use a super-stretchy fabric. It’s very easy to get your arm through it. You can pull your arm straight through because, when they’re on the podium, they don’t want to be standing there messing around with their clothes.
[So these are the official new colours for all the jerseys, or can they still be adjusted?]
Yellow are final, and what’s really cool about the yellow is that we wanted to add a pigment that reacts to UV light. When the sun hits it, it becomes really vivid. I don’t want to say fluorescent, but it’s loud. For me, the yellow jersey should almost act like a light in the peloton. When you see it from the helicopter camera, it should go, “Boom!” Take it outside into the sun and it really lights up.
We added a fluorescent pigment to the colour.
[Are there any differences between the polka-dot jersey and the yellow one? Since it’s for climbing, maybe the materials should be lighter overall?]
In that sense, no. They also get the ultralight version in this form, but all four jerseys use the same materials.
What I like about this one is that we’ve hidden the scorpion inside the polka dots. The other jerseys have the Castelli wordmark, but on the polka-dot jersey we use the scorpion to respect the polka-dot design. I think you can see it on the back.
[Do I remember correctly that you said the logo could also be adapted to different colours? Maybe not for the Tour de France jerseys, where you might want to keep the original red one, but is that happening in general?]
Yes. In the main collection, we’ve started moving away from the red scorpion. We really reserve it for innovative pieces like the Gabba and Gabba R. Those are iconic innovation products that need the red scorpion.
Previously, the scorpion was always red, and the question was where we were going to put it. Now it can be used in any colourway, so it becomes part of the design. It’s included in the design process rather than being the last thing we add.
[For the winner’s jerseys, it makes sense to keep it visible, with enough contrast...]
It’s the most visible sport in the world, and the red scorpion works well for that. I think it’ll take time for people to get used to other colours because the red scorpion is iconic in cycling. If we suddenly turned up at the Tour de France next year with a yellow scorpion, people would be like, “What?”
But for Paris-Nice – and I keep calling it the Critérium du Dauphiné – the scorpion isn’t red. For me, the yellow jersey of the Tour de France is the yellow jersey. Paris-Nice also has a yellow jersey, but it shouldn’t be the same as the Tour’s. Some riders can win Paris-Nice, but not everyone can win the Tour de France, so the jerseys shouldn’t be the same.
At the moment, there’s a line across the jersey to distinguish it from the Tour’s, but we wanted to make it even more different. So the scorpion for Paris-Nice isn’t red, and for the Dauphiné it’s another colour. That helps each race develop its own character.
This one will be announced on Friday. It’s the new white jersey, and the skinsuit will also come with purple bib shorts.
The green one isn’t quite right here because the colours aren’t accurate. They’re very strict about their colour, so we have to respect the brand guidelines.
What’s cool, though, is that the jersey used to be all one colour. When we were first introduced to them, I said it needed to be visible. I’d always found it hard to see. They were very accommodating and let us change the sleeve.
This jersey is worn in the sprints, which is an iconic position for TV coverage and so on.
[For bad weather, when it’s raining, is there a yellow jacket too?]
Yes, they have the Gabba, and it’s fully yellow as well. The difficult part is that you have to print it, using the exact white box inside it.
The jackets will be made from Polartec AirCore, in a printed version.
We worked with Polartec to find a way to print on that fabric because, once you print on it, you compress it and lose the loft.
It was really good fun working with them on that, and now the entire jacket is fully sublimated, with the white box printed on it.
Another part of the process was sending the jerseys to ASO with the white box and the front zip in place, so they could see how it would look when they pressed their logos on top. We had to do the same with the jackets made from Polartec AirCore, to check that when ASO used its machines to press the sponsors’ logos on at the end of a stage, everything would fit perfectly. It’s very technical stuff. We sent them samples in June and July so they could do all the print testing.
[And are there any differences with the bib shorts?]
They don’t get bib shorts, so they wear their team ones.
[But I think I remember Pogačar wearing yellow bib shorts too, or was it other riders as well?]
It was really strange this year because he wore black. There were two stages where he changed from yellow to black, which was like, “Whoa!” We hadn’t seen that before.
Almost all the riders now wear skinsuits. There are a couple of exceptions where riders want to wear their shorts and pad, and just the jersey.
At the end of every stage, when they go onto the podium, if it’s a new rider who has just taken the yellow jersey, someone from ASO drives to the hotel and gives them a package with a jersey and a skinsuit. They then check the weather and say, “Okay, over the next two days, you’re also going to need the jacket.”
The rider keeps those items for two or three days, and then we give them another set.
It’s not decided by us; it’s decided by ASO. They don’t wake up every morning to find a brand-new skinsuit on their bed. It doesn’t work like that.
[I’ve also seen some team vlogs where they wash everything after every stage. You can get new stuff, of course, but it’s not like that every day…]
No, they don’t do that. It’s up to the rider to decide whether they want the skinsuit. I guess now, because we have the normal skinsuit with the normal jersey, they can also choose the ultralight version, which would be cool.
The women’s jerseys are the same, by the way. Only the cut and shape are different.
[From your perspective, perhaps from the product side, what impact will it have for Castelli to be at the forefront of cycling racing overall? I know it’s huge for the brand, but what are you thinking from the product perspective?]
For me, it’s going to be cool to have the top riders in the world wearing it. If you look at our rain jackets and rain products, almost all the riders go to our website and buy them at full price. We know because we see the orders, and then we see them turn up at races. So professional riders obviously love Castelli products.
Now the best riders in the world will be wearing these products in the biggest race in the world, which is great from a product perspective.
I really hope to get to as many races as possible, to be alongside Pogačar, Del Toro, Seixas, Merlier and the others, and understand more about what they need.
We already get a lot of feedback from our team, Soudal Quick-Step. We work really closely with them on product feedback. They helped us develop the new chamois coming next year, for example. Any feedback and product development you can get from the top riders in the world is valuable to us.
It’ll be really cool to see the podium on the Champs-Élysées and, as they walk off, ask them a few questions: “What about the sleeve length? Did it fit you? Was it working for you?” That’s going to be really cool for me.
It’s not just about seeing the logo on TV. That’s amazing, don’t get me wrong – it’s super special. But personally, it means a lot to me. I used to work in a bar, a pub in Scotland, and there was a guy who came in every single day and always asked to put cycling on the TV. We usually had football on, because it was a Scottish pub, but he always asked for cycling. I used to think, “This guy, man, why does he keep putting cycling on?” So we’d put it on, and he’d sit at the bar, drink his Guinness and explain what was happening: “They’re in the breakaway; the team isn’t working.” He basically taught me the sport when I was 18, 19, 20 years old.
So now, at 38, to have the yellow jersey here on this table, with the Tour de France starting in Edinburgh next year, it couldn’t be more special for me.
[Is the guy still alive?]
Yeah, yeah. Peter is still around, for sure. He’ll be a guest of honour.
I like it because it’s a full-circle moment: sitting in the pub, listening to the guy talking about cycling.
[How long ago was that?]
Twenty years. It took me a long time to get here, but it’s been a good journey.
Even at school, I was really bad. I didn’t care, and I wasn’t really in the mood for learning. My English teacher, Mrs McFarland, gave me a book to read. She said, “Read this book,” and it was the autobiography of Lance Armstrong. It was actually the first book I read at school. Then I went away and wrote a full report on it. So I’ve always had little bits of cycling in my life.
[That’s so cool. I appreciate you sharing all these insights.]
Our last interview with Eva was four years ago – for our TECHUNTER 07 ONLINE issue. As you all know, the world has changed dramatically since then – and continues to evolve. One thing that hasn’t changed, however, is Eva’s and Houdini’s unwavering commitment to protecting nature while leading an outdoor apparel company – the task, we should say.
There’s still much to be done and many conversations to be had – so we hope this interview also offers some valuable insights for you. It’s time to do more.
Check out our other relevant articles via the links below.
Article and images prepared by TECHUNTER Magazine.*
Answers: Eva Karlsson [HOUDINI SPORTSWEAR, Chief Creative Officer]. Questions, words, photography: Alexander Zabelin [TECHUNTER, Chief Editor]. Special thanks to Romsdal Lodge & Houdini Sportswear for a great hospitality!
*All images above, as well as those on every page of this website, are the property of TECHUNTER Media and may not be used, reproduced, or distributed without explicit permission from the source.