President of ECIS Prof. Dganit Danino

Department of Biotechnology and Food Engineering and the Russell Berrie Nanotechnology Institute
Haifa, Israel

With deep sorrow we announce that Peter Kralchevsky, Secretary of ECIS, had suddenly passed away on December 6th, 2020. The European Colloid and Interface Society has lost one of its most eminent scientists, who had been also deeply involved in the development and consolidation of the colloid and interface community in Europe. Peter’s research contributions in the domains of capillary and surface forces, colloidal dispersions and surfactants (adsorption, micellization, micellar growth, solubilization and rheology), attachment of particles to interfaces, as well as interactions in colloidal and bio-colloidal dispersions, are published in more than 200 manuscripts and are already in textbooks. His latest Lyklema plenary lecture at the ECIS2020 on-line Conference in September 2020, named “Capillarity and Self-Assembly”, summarized in a perfect manner his most recent remarkable accomplishments to the development of the new knowledge in the field of colloid science. Peter was an active participant one of the Holy Grails in nanoscience research: How to extend the DLVO approach to take into account steric interactions and subtle entropy effects in solvated layers in order to increase parameter-free predictive power of this theory as well as compatibility with thermodynamics.

Peter Kralchevsky moreover pioneered aspects on solid (nano)particles at fluid interfaces where the molecular, colloidal and mesoscale capillary forces combine. This work is well described in the first monographic book “Particles at Fluids Interfaces and Membranes: Attachment of Colloid Particles and Proteins to Interfaces and Formation of Two-Dimensional Arrays” (Elsevier, Amsterdam, 2001, co-author Kuniaki Nagayama) which was devoted to the behavior of colloidal particles at interfaces and in thin liquid films. These studies started an important new field in colloid science which comprises nowadays the design of new types of nanomaterials and important developments related to fine-tuning and stabilization of foams and emulsions without surfactants. These composite materials have a high application potential for the creation of novel materials for analytical and diagnostic approaches in medicine, and for other technological advancements.

The entire professional career of Peter Kralchevsky was linked to Sofia University. In 1981 he graduated Physics and started his academic career in the group of Professor Ivan Ivanov in the Department of Physical Chemistry of the Faculty of Chemistry. He received his PhD in 1985; became associate professor in 1991 and full professor in Condensed Matter Physics in 2002. For many years Peter headed the Laboratory of Thermodynamics and Physicochemical Hydrodynamics (1993–1999), the Laboratory of Chemical Physics and Engineering (2000–2008), and the Laboratory of Complex Fluids (2017–2020). He was also the Dean of the Faculty of Chemistry and Pharmacy at Sofia University (2015–2019). In 2012 Peter was elected a Fellow of the Bulgarian Academy of Sciences.

Peter was an author and lecturer of many University courses, and he had supervised numerous BSc and MSc students, as well as more than 15 PhD Theses. Peter was not only an eminent representative of the Bulgarian Colloid Chemistry community but also a kind and supportive teacher and colleague. His diverse scientific and teaching activities had brought him distinction, both national and international. He was recipient of the Prof. A. Zlatarov Prize of the Bulgarian Academy of Sciences and the Sofia University (1990); “St. Kliment Ohridski” University of Sofia Blue Ribbon Medal for significant achievements in science (2006); Annual award “Best Professor” (2007), and the highest National Award “Pythagoras” for scientific achievements (2016) of the Bulgarian Ministry of Education and Science. In 2020 Peter Kralchevsky was awarded the first ECIS – Lyklema Prize, in recognition of his outstanding scientific achievements and exceptional contributions to ECIS organizational activities and to the colloid community development. Link to the lecture

Peter Kralchevsky was a key actor member of the European and also International colloid community, and devoted to the development of ECIS (Secretary since 2010) and the joining of Eastern and Western Europe to the ECIC society. As Chair of the European COST Action D43 Colloid and Interface Chemistry for Nanotechnology (2008–2011) and Vice-Chair of COST Action CM1101 Colloidal Aspects of Nanoscience for Innovative Processes and Materials (2012–2016) his actions catalyzed hundreds of scientific contacts between formerly Eastern and Western European science.

In 2015, Peter was elected as a Member of the Council of the International Association of Colloid and Interface Scientists (IACIS, initiated by Hans Lyklema in 1957).

The death of Peter Kralchevsky is a significant loss to the European colloid and interface community. The legacy of his scientific contributions and his long-term service to the ECIS community will always be remembered.

доц. Лариса Царькова

МГУ „M. B. Ломоносов”, Москва

I’m stunned by the news that Peter has passed away. I’m so sorry for this unimaginable loss and I express to you and to your department my deepest condolences also on behalf of my colleagues, who were lucky to know Peter.
I wish you strength and courage to go through this difficult time and to carry further what he created and achieved during his bright scientific life.
It is hard to add any words to this great loss, which you will be still feeling for many-many years. I hope that his scientific life will be continued further in his students, by his colleagues.
May he rest in peace.


We were deeply moved by the sudden loss or Prof.  Dr. Peter Kralchevsky. Peter was one of the most eminent scientist in the field of interfacial and colloidal science worldwide. We are grateful for the numerous enlightening and fruitful discussions we could have with him over the last years. Our contact with him was not only scientifically inspiring but also extremely pleasant on the personal level and accompanied with his wonderful sense of humour. We will always remember his legacy.

Our deepest sympathy is now for his family and his closest friends around him.

Dr. Thomas Willers

Carsten Gerber

Dr. Christine Bilke-Krause

Dr. Robert Minch

Dr. Marlitt Jönsson

Florian Weser

Cornelius Weser



проф. дхн Г. С. Георгиев

Факултет по химия и фармация, СУ

Съболезнования за семейството и близките му.
Почитания към добрия ЧОВЕК, излъчващ добрина, светлина, спокойствие, сигурност, скромния и систематичен работохолик,творящия учен, получил световно признание за постиженията си в областта на химичната физика на колоидни системи и повърхности. Дано следовници и ученици намерят сили и умения да развият богатите му идеи!
С дълбок поклон и почит,
проф. дхн Г. С. Георгиев

Dr. Rossitza Alargova

Infinity Pharmaceuticals

A star has fallen…With a very heavy heart sharing the sad news about the passing away of my beloved mentor, friend, and PhD advisor Prof. Peter Kralchevsky due to COVID19. A beautiful mind, a scientist of extraordinary magnitude, a wonderful teacher and mentor, and beyond all, a great person, he will be sorely missed by the scientific community and all of us who had the privilege to cross paths with him. Rest in Peace, Dear Prof. Kralchevsky, you will always be in our hearts! Sending my deepest and most heartfelt condolences to his family.

Факултет по химия и фармация, СУ

проф. Георги Вайсилов

Искам да изразя съболезнованията си към семейството на акад. Кралчевски и към колегите от катедрата по Инженерна химия и фармацевтично инженерство. Акад. Кралчевски беше пример за всички нас както като водещ учен, така и като човек и личност. Светла памет на акад. Кралчевски!

Unilever R&D, U.S.A.

Dr Anat Shiloach

Beyond the contributions he’s made to our collaborations over many years, I also had the chance to get to know him a little bit better when I visited Sofia in January and I very much enjoyed our conversations. For such a close-knit department and academic community this must be difficult, and I extend my condolences to you and to his family and colleagues.

Unilever R&D, U.S.A.

Dr Joseph Carnali

Please let his family know that his collaborators here in Trumbull express their sincere condolences to them and to his departmental colleagues. Peter’s approach to problems was always a breath of fresh air to me and I very much enjoyed our long-distance collaboration. During my visit to Sofia a number of years ago, it was obvious how integral a part he has played in the development of the department. His many contributions to colloid and surface science will long be remembered, as will the many strong collaborations he fostered. I am also sure that the positive effect he had on his many students will be a lasting memorial.

Unilever R&D, U.S.A.

Dr Prem Chandar

I was shocked and saddened to hear about Peter. Just wanted to convey my deepest sympathy to you and the wider Sofia family at this time of grief. I will always remember Peter as a brilliant academic who was willing to tackle complex problems and with the rare ability to translate insights/experiments into enduring mathematical models. I fondly remember the many interactions with him where his energy and enthusiasm was always on display and served a role model for many younger scientists here in Trumbull. I will miss him dearly.

Unilever R&D, U.K.

Dr Ian Howell

So very sorry to hear your news, it’s very difficult to take in. I have so thoroughly enjoyed working with Peter; he was simply outstanding.

Unilever R&D, U.K.

Dr Joanne Cook

I wanted to say how very sorry I am that this has happened. I enjoyed working with Peter so much – he was a giant in the field of colloid science, but also a truly lovely person to work with. You must all be terribly shocked by this. Peter was a highly respected and valued collaborator of Unilever over many years.


Dr. Juergen Tropsch

I will definitely miss the intellectual challenge to follow his ideas in the presentations/lectures I was listening to. It is also a big loss for the scientific community and all his colleagues and friends in Sofia.


Dr. Frederic Bauer

His mathematical understanding was truly awesome. I will try to keep the nice moments in mind like some of the lectures I could listen to or the meetings in the frame of our collaboration. As a great one he will stay in memory.

School of Engineering and Materials Science Queen Mary University of London

Dr. Radomir I. Slavchov

За човек който слабо познавах, професор Кралчевски остави диря в живота ми. Беше страхотен преподавател – в направление Физикохимия, двата часа лекции в петък с него си бяха изпитание и за ума, и за мускулите на ръцете (средно по 40 страници изписвахме!), но и до днес правя един куп пресмятания по методите които той ни преподаваше, а не по тези от книгите които прочетох след това. Собствените ми лекции днес носят неговия отпечатък. Тогава – млади студенти на по двадесет години – най-много ни ядосваше методът “умен съм бил, сетил съм се”, с които професорът съкращаваше някои изводи четворно. Имаше един виц – щом е в квадратна кутия, сигурно е кръгло, значи е оранжаво, т.е. в кутията има портокал – професор Кралчевски правеше същото познавайки решението я от граничните условия, я от някоя друга област на науката, или пък просто от какво ни се ще да е това решение. Ние хич не успявахме да се сетим на изпита… Но дори и това остана – не една работа сме писали със сътрудници с употреба на “умен съм бил, сетил съм се” по Кралчевски. Следа у мен, вече като докторант, остави и книгата му с Накаяма, с която и до днес често се консултирам (викаме и “библията” с колегите, май само на Ландау и Лифшиц сме използвали такава силна дума). И вече дълги години в малко от моите собствени публикации пропускам да цитирам някоя и друга работа на Кралчевски и колектив. Голям ум, без съмнение, и пример за нас, по-младите. Почивайте в мир, скъпи учителю. Моите съболезнования за семейството и приятелите му.

Катедра Физикохимия, Факултет по химия и фармация, СУ

Проф. Стоян Гуцов

Бих искал да изкажа дълбоките си съболезнования към семейството на академик Петър Кралчевски. Петър Кралчевски беше изключително почтен човек, голям учен със световна известност и впечатляващ лектор. Поклон!

Катедра по инженерна химия и фармацевтично инженерство, ФХФ, СУ

Д-р Гергана Ценова

Една голяма загуба за България, за света, за науката, за човечеството… за мен… На 5 декември, битката с коронавируса загуби моят научен ръководител акад. проф. Кралчевски. Един прекрасен човек и ментор, един достоен пример за българското общество, един велик учен… Всичко казано за него би било малко… Светъл да е пътят Ви. Радвам се, че точно Вие бяхте мой ръководител и “баща” в науката. Винаги ще Ви помня. Всички осиротяхме… Съболезнования на семейството, приятелите и колеги.

НИС – СУ “Св. Кл. Охридски”

След дълги години съвместна работа, винаги ще помним академик професор Петър Кралчевски с неговата топла, излъчваща доброта и спокойствие усмивка. Дълбок поклон пред паметта на прекрасния човек, голям учен и приятел на НИС! Присъединяваме се към скръбта на неговите близки и колеги! Вечна му памет!

От колектива на НИС при СУ “Св. Климент Охридски”

Катедра по инженерна химия и фармацевтично инженерство,

Д-р Румяна Станимирова

Много е трудно да приемеш такава новина, че такъв човек като акад. проф. Кралчевски вече не е сред нас. Много е трудно да се говори за него в минало време. Той беше/ е изключителен човек, велик учен, толкова ерудиран и вдъхновяващ, винаги ни е бил за пример и не само на нас хората, които работихме с него, а и за всички, които по някакъв начин са се докоснали до него. Трудно се осъзнава, че няма да ти звънне телефона и да му чуеш гласа. Това е една огромна загуба за България, за европейската и световната наука, за всички нас. Всеки ден или през ден съм му писала имейли които започват с обръщението „ Драги, проф. Кралчевски“ сега ще е последния, който ще напиша адресиран към него:

Драги, проф. Кралчевски,

Благодаря Ви за всичко, на което ме научихте! Благодаря Ви, че с вашата всеотдайност, доброта и спокойствие винаги ми помагахте, когато имах нужда. Благодаря Ви, че имах възможност да работя с Вас и да се уча от Вас. Винаги ме изслушвахте, когато имах проблем и с лекота го решавахте.

Вие оставихте в съзнанието ми, живота ми и научното ми развитие огромна следа, за която съм Ви изключително признателна и благодарна.

Радвам се, че имах възможността да работя с вас по различни проекти и имах възможността да черпя с големи шепи от неизчерпаемите Ви знания и да се уча от Вас.

Винаги ще си спомням за вас с огромна благодарност за всичко, което сте направили за мен, ще ви запомня с леката усмивка и с човечността Ви.

Светъл полет във вечността!

Сигурна съм, че ще продължите да ми помагате да взимам правилни решения по някакъв начин!

С голямо уважение и последно сбогом!


Faculty of Physics,
St. Kliment Ohridski the University of Sofia

Prof. Dr.habil. Georgi Rainovski Dean of Faculty of Physics

Уважаеми колеги,
моля приемете съболезнованията от колегията на Физически факултет.
Поклон пред паметта на проф. Кралчевски и мир на праха му!

От името на колегията на Физически факултет,
Георги Райновски

Факултет по химия и фармация, СУ

доц. Людмил Лютов

Поклон пред паметта на Колегата, Човека и Приятеля

П. Кралчевски!

Несъмнено заслужените високи титли и длъжности не го възгордяха и не промениха отношението му към околните и низшестоящите. Той запази тихия и спокоен характер до края на дните си. Колегиума загуби не само ерудиран учен, но и изключителен Колега, Човек и Приятел. Последно Сбогом!

Max Planck Institute of Colloids and Interfaces
Science Park Golm
Potsdam, Germany

Dr. habil. PD Rumiana Dimova

The loss of Peter Kralchevsky (Petio) is an overwhelming news. As one of his PhD students 20 years ago, I realize that his great scientific insights, wonderful personality and excellent didactical skills have shaped me as a scientist more than I can grasp. I write this email with great sorrow and hope that his legacy in the field of colloidal physical chemistry remains appreciated for long years.

Хумбултов съюз в България

проф. Лора Тасева (Председател на ХСБ)

Уважаема госпожо Кралчевска, опечалено семейство и колеги,
Хумболтовият съюз в България изразява своите искрени съболезнования на семейството, близките и колегите на академик Петър Кралчевски по повод неочкваната му кончина. В негово лице българската наука и образование изгубиха един изключителен учен, преподавател и колега с висок професионален и човешки морал.
В нашите спомени акад. Кралчевски ще остане и като добър приятел на Хумболтовия съюз в България, който винаги откликваше на всяка молба за съдействие. Ще го запомним и с участието му в Хумболтовите лекции през 2016 г., както и с подкрепата му като декан на Факултета по химия и фармация на наши колеги-хумболтианци в техните съюзни изяви.
Да бъде светла неговата памет!

Division of Physical Chemistry Department
of Chemistry Faculty of Science, University of Zagreb

Prof. Davor Kovacevic

I am really sorry to hear the sad news about Prof. Kralchevsky. I am sure that his scientific and personal achievements will be remembered not only at your University and in Bulgaria, but also in European colloid community generally. ECIS meetings and other events without him won’t be the same any more, we have lost an outstanding colleague and friend. Please pass my respect and condolances to his family and friends.