Welcome at Challenging Glass! At this 9th edition of the conference, we are thrilled to welcome no less than 120 presentations - a record since the first edition of this international event back in 2008. Ever since, we have been keeping up our high standards in sharing knowledge, science and best practices on glass engineering and design. Thanks to the great work of bright authors and sharp reviewers, that is not different this time. What actually ís different this edition, is the introduction of a Glass Circularity Debate. We have seen several trends come and go over the past years, but the importance of circular design is to stay! Therefore, on top of the regular technical sessions on the topic, we bring five speakers to the stage who will pitch their views on the circular use of glass and discuss it with each other and the audience. You are warmly invited to actively participate! Furthermore, we are happy to welcome no less than five top-notch keynote speakers. The first keynote will focus on the Mirage project and will be delivered jointly by Dr Faidra Oikonomopoulou, Dr Telesilla Bristogianni and Mr Alexandros Cannas. The second keynote will be presented by Dr Peter Zoon, who will explain how glass plays an important role in crime scene investigations. It promises to be a criminal talk! Last but not least, Dr Corentin Fivet will share his work on new design paradigms for reuse during his closing plenary lecture. During the conference you will be able to retrieve all abstracts and papers, but also presenter details and programme updates with our conference app. After the conference, all papers will be available online, either through our online proceedings platform or through the peer-reviewed journal Glass Structures & Engineering (SpringerNature). We explicitly like to thank the continuous support of our sponsors, Scientific Committee members, authors and attendees. Together with you and with our co-hosts James O’Callaghan, Mauro Overend and Fred Veer we are eager to kick off Challenging Glass 9! Christian Louter, Freek Bos and Jan Belis June 2024