String expert Sandra Kirschbaum in an interview: about the traditional company Kirschbaum and the world of strings

In today's episode of our "String World" series , we interview Sandra Kirschbaum about tennis strings and their importance to every player. It's fascinating to learn how the family business has developed over the past 35 years. But not only the company, the world of strings itself has changed immensely in recent years.

Let Sandra take you on a journey through time and show you how to find YOUR perfect tennis string

Sandra, you are THE expert on strings and stringing. How did your love for tennis strings begin?

I'll take the title "THE expert" as a compliment. There are indeed many, many experts in this field among stringers and racket tuners. But I'm perhaps the most diligent when it comes to individual consultation and support on the equipment supplier side. This is probably due to the passion with which we've worked in our family business for 35 years – I would be nothing without my team. Since we've always specialized in tennis strings, we've had thousands of conversations over the years with players, stringers, shop owners, coaches, parents, and tournament organizers. I've never played at a professional level myself, but over the years I've spoken with hundreds of professionals, listened to them, and tried to understand how they think and what they expect from their equipment. 

Tell us something about your company. Where are you located, how many employees do you have, where do you produce? In which countries do you operate? Do you only sell the strings directly, or what distribution channels do you have?

We've been based in Witten since 1987. My father founded the company with his wife, with whom he had previously run a successful real estate agency and a hair salon 😉 My father was a creative, self-made man with a go-getter wife by his side. I joined the company in 1991, and together we built up our sales network outside of Germany. Kirschbaum strings are available from Australia, through Asia and Europe, to North and South America. We've been working with some partners for over 25 years. We also have a long-standing workforce; some have been with us for over 20 years. Horst sadly passed away in 2010, but my mother is still involved. We have a total of 14 full-time and part-time employees. Our core products are made in Germany, we hold patents for surface treatments, and worldwide sales are handled from our headquarters in Witten.

Your company, Kirschbaum, has been on the market for 35 years. Take us on a brief journey through that history. What technological developments have there been? How has the market, and your company, evolved?

Between 1985 and 1987, my father and a partner experimented with new string materials and manufacturing techniques using converted cable industry machinery. They quickly acquired their first extruder. After several trials and initial test runs, my father launched in 1987 as a supplier to major racket manufacturers – essentially providing OEM products. He rapidly established strong contacts and secured regular orders from companies. Soon, a partnership with a racket manufacturer led to the production of a Kirschbaum racket series called "Independant," featuring an adjustable grip. This series was unveiled at the ISPO trade fair in Munich, still located at the old exhibition grounds, at their own booth. Simultaneously, the first polyester strings in white and natural finishes were introduced, marketed under the product names GUT FEELING, SUPER SMASH, and LONG LIFE, and sold under the Kirschbaum brand. The logo at that time was a sweetspot-filling tree, which was replaced by the cherry tree in the early 1990s. The strings quickly gained popularity and became widely adopted by serious table tennis players. Marketing the racket proved difficult for a tennis newcomer lacking the necessary capital, and efforts were discontinued. The focus shifted to the strings and the Kirschbaum brand name. Interest among top-ranked German players was piqued. The first hybrid string, named TOUCH DUO, was born – a 1.35 mm polyester string for the mains and a 1.25 mm polyamide string for the crosses.

With the expansion of distribution beyond Germany starting in 1991, the company established strong relationships with professional players, particularly in Spain, Italy, and South America. Western grip and topspin techniques led to increased string wear and a growing demand for polyester strings. The breakthrough came after 1996 with the relaunch of SUPER SMASH - HONEY – the first polyester string in a beautiful color, with a reduced pigment content, and, most importantly, available for the first time in seven individual diameters: 1.225, 1.275, and 1.325 mm. The response from players was tremendous. Many young and adult players in Germany and internationally quickly became brand ambassadors, sporting the iconic cherry logo. In 1997, the SUPER SMASH SPIKY followed, a string with a patented surface profiling. In the late 1990s/early 2000s, every second ranked player with the "cherry" as a logo (including Mischa Zverev, Florian Mayer, Angelique Kerber, Anna-Lena Grönefeld and many more) played among the top 800 of the ATP/WTA over 300 players (including Carlos Moya, Dominik Hrbaty, Karol Kucera, Guillermo Canas, Gaston Gaudio, Patty Schnyder, Anastasia Myskina, Caroline Wozniacki, Vera Zvonareva).

The company grew, exporting to 50 countries, with mail-order companies and sporting goods stores serving tennis enthusiasts in Germany. Tennis strings also became a key component for racket manufacturers, and due to increasing competition among top racket brands, which only allowed their own logos on their contracted players, the second logo of string sponsors gradually disappeared – and so did the cherry. To be honest, competitive pressure also increased among pure string specialists, leading to significantly more market penetration – while Kirschbaum, as a family-run business, was somewhat weakened by the founder's illness and the birth of our two children.

Other important products of the early years were the multifilament string PX12, the TOUCH TITANIUM (test winner Tennis Magazine 99), and later the GUT FEELING (test winner Tennis Magazine 2017).

The new sales channels through the internet, online retailers, global trade, and the pandemic have presented us with new challenges. But our direct contact with customers, stringers, and players, our quality products, and our excellent service ensure consistently strong sales figures, and the positive feedback reinforces our approach. Now we need to focus on raising brand awareness among younger players and continuing to supply all other age groups with consistency and product variety.

What potential actually lies in the individually "optimal" string?

So, what's the ideal string? It doesn't have to be the most expensive, it doesn't have to be the newest. What's needed is the string that's the perfect match for the player and racket, the string the player feels comfortable with and with which they can play their best tennis. Honestly, even our strings can't perform miracles. But if the string isn't right, it will hinder the player, and in the worst case, it will cause them strain. There's a lot of need for information here, and ideally, a personal consultation is necessary – you can't make a blanket statement. That's why we offer every player a consultation form on our website ( www.kirschbaum-strings.de/beratung ). The string can certainly influence the length and speed of the balls, as well as their trajectory. Durability should play a secondary role in this.

Why do you think so many tennis players neglect the topic of "strings"?

In the professional/tournament scene, the importance of the string, its diameter, and string tension, and the influence they have, is well known. Many recreational players, however, never encounter this because they've never received any advice on these matters. Coaches often don't have the time to discuss these topics in training, so players grow up without an awareness of the string's importance. Stringers and sports shops also rarely have the opportunity for a genuine consultation with a customer, and unfortunately, when it comes to money, customers often aren't receptive to tips that might even lead to higher stringing costs. It's a complicated situation. And then there's the sheer volume of products available, overwhelming interested users with offers, products, forums, and recommendations. It's easy to lose sight of the goal.

How do I find the right string for me? What's the best way to go about it? What do I need to consider?

As I said, anyone can get advice from us. But regardless, here are a few tips: Choose the thinnest string possible while still being satisfied with its durability. A thinner string provides better spin. Choose the lightest possible weight so that the racket still offers good overall distance control. Less weight reduces strain on your arm and also increases durability. Don't play with polyester strings for too long – the material isn't designed for that. The strings also lose quality over time. You adapt to the strings without realizing it, and this doesn't help solidify your technique. As a rule of thumb, you should change your strings at least as often as you play per week during the season. For players who don't experience string wear, I would recommend trying a polyamide string instead of polyester – don't be put off by the slight slippage. That's not a sign of poor quality.

How long have you been playing tennis? Do you still play? If so, how often?

I started playing tennis as a child and had training. In my teens – when tennis was really booming 😉 – I played on the women's team; it was very competitive and ambitious. Unfortunately, that took the fun out of it for me, and puberty didn't help. I only started playing again later with my own children. So I was never a professional, nor do I play at a professional level myself.