R59-1 (Sichem), 1959 Lacquer paint, gauze, paper and cardboard on board, 47 x 64 cm Courtesy BorzoGallery, Amsterdam
R59-2, 1959 Lacquer paint, gauze, paper and cardboard on board, 52 x 81,5 cm Private collection
It is remarkable that Jan Schoonhoven produced both monochrome white and polychrome reliefs in 1959. Two consecutive ‘numbers’, the reliefs R59-1 and R59-2 (both 1959), are prove of Schoonhoven's lust for experimentation. And they also show that the artist was anything but rigid in his views.
From correspondence and testimonials from contemporaries we know that an exhibition by Italian artist Piero Manzoni (1933-1963) in the Netherlands had a major influence on Schoonhoven's choice for the ‘non-color’ white. That this development took place reluctantly, is evident from the first numbered reliefs from 1959. Relief R59-1 is emphatically white, and always has been. The next relief, however, R59-2, has a polychrome skin that we usually associate with Schoonhoven's reliefs from the Informal period.
Between November 1957 and January 1958, Piero Manzoni started creating the canvases dipped in porcelain clay that from 1959 onwards were given the designation Achrome, ‘colourless’ works. In the Netherlands, Hans Sonnenberg was the first gallery owner to have an eye for Manzoni’s monochrome white works. In September 1958, the Rotterdam Art Circle organized Manzoni’s first Dutch solo exhibition. Jan Schoonhoven visited the exhibition in the company of artist-friend Jan Henderikse. Schoonhoven was bowled over by the exhibition, Henderikse recalls: “It was a real blow to us to see work that was this provocative. Jan [Schoonhoven] was enormously impressed by the order in Manzoni’s work. And everything was white, of course, white as a sheet!” 
What artists such as Schoonhoven and Henderikse recognized in Manzoni was expressed most aptly by Schoonhoven. Manzoni’s Achromes demonstrated the need to “(...) dispense with the last remains of the superfluous. We’d thought that in our work, we’d achieved a completely objective method of creating, but it turned out (…) that our method was no longer feasible.”  In the course of 1959, Schoonhoven provided several existing, polychrome reliefs with a new layer of white paint. Hans Sonnenberg remembers that Schoonhoven refered to these works as ‘my Manzoni-reliefs’. 
The reliefs R59-1 and R59-2, however, still have their original appearance. They provide a glimpse into everyday artistic practice - and show us that some revolutions take place step-by-step.
Notes:  Jan Henderikse in conversation with the author, February 11, 2011.  Jan Schoonhoven in a letter to a German collector, 21 March 1971, quoted in: Antoon Melissen, Jan Schoonhoven, Rotterdam 2015, p. 55-56.  Hans Sonnenberg in conversation with the author, 23 May 2011.
Further reading: - Colin Huizing and Julia Mullié (eds.), Manzoni in Holland, exhib. cat. (Schiedam: Stedelijk Museum Schiedam), 2019. - Antoon Melissen, Jan Schoonhoven, Rotterdam 2015.
Jan Schoonhoven rarely made such elaborate notes on the reverse side of his reliefs as in the case of R70-38 (1970), acquired by German photographer Lothar Wolleh in the year of its creation. But above all, Schoonhoven's text is a curious case of Dutch sobriety.
27/6 '70. I took a look at this work, here at Lothar's place. He told me that it fell to the floor. Doesn't matter! This work of art is for Lothar, Mrs Wolleh and Ollivier. Jan J. Schoonhoven
R70-38, 1970 (reverse, detail) Emulsion paint, paper and cardboard on wood, 124 x 84 cm Private collection
Exhibition poster with a detail of Jan Schoonhoven's relief R61-5, Jaloezieënreliëf (1961), third line, second from the left
In March 1965, Italian architect and artist Nanda Vigo exhibited in Hans Sonnenberg’s Galerie Delta in Rotterdam. On that occasion Vigo also visited Jan Schoonhoven in his hometown Delft. Vigo had fond memories of Jan Schoonhoven: "When I think of him I can only smile", she told me in 2014.  With her passing, March 2020, generation ZERO lost one of its most colourful personalities.
The days before the opening of Nanda Vigo's exhibition in Rotterdam, Hans Sonnenberg hosted a joint visit by Vigo and Yayoi Kusama. Sonnenberg, who was a regular guest in the Schoonhoven home, decided to introduce them to the family. "They were kind of in my way that day, I was busy", Hans Sonnenberg recalled. "So I lent them my deux-chevaux to visit the Schoonhoven’s in Delft." 
The artist’s son Jaap Schoonhoven remembers that trip and the times in later years, when Nanda Vigo stayed overnight at the family’s home in Delft. Discussions about art were sometimes laborious; Vigo spoke English and French, but Schoonhoven did not, or hardly.
Some half a century later, Nanda Vigo still remembered Jan Schoonhoven as a kindred spirit and an influence on her own work. "We did not speak each other’s language, and communication was not always easy', she told me. 'Our approaches differed, as did our strategies. But we understood each other’s work, we felt a deep connection. Even without talking." 
A photograph from 1969 shows one of Nanda Vigo's Cronotopo's in Schoonhoven's living room. JanSchoonhoven returned the favour and gave Vigo one of his reliefs in exchange. There was indeed, as Vigo recalled it, 'un affetto speciale' between the two, a special affection.
Notes:  Nanda Vigo in conversation with the author, 12 May 2014.  Hans Sonnenberg in conversation with the author, 23 May 2011.  Nanda Vigo in conversation with the author, 12 May 2014.
'Zero Avantgarde 1965' In 1965 Nanda Vigo curated an exhibition at Lucio Fontana's studio in Milan. The exhibition 'Zero Avantgarde 1965' was a truly international presentation, even beyond the European context. Until the end of 1966, the exhibition toured several Italian cities, including Brescia, Rome and Milan.
Participating artists: Bernard Aubertin, Hans Bischoffshausen, Lucio Fontana, Hermann Goepfert, Hans Haacke, Yves Klein, Walter Leblanc, Heinz Mack, Piero Manzoni, Christian Megert, Henk Peeters, Otto Piene, George Rickey, Jan Schoonhoven, Jesús Rafael Soto, Ferdinand Spindel, Paul Talman, Erwin Thorn, Günther Uecker, Jef Verheyen, Nanda Vigo, and Herman de Vries
Studio of Lucio Fontana, Milan, 27 March–May 1965
Galleria del Cavallini, Venice, 4–14 May 1965
Galleria Associazione Zen, Brescia, 15 October–4 Nov. 1966
From the Archives of the Lothar Wolleh Estate, Berlin
In autumn 1969, German photographer Lothar Wolleh visited Jan Schoonhoven in his hometown Delft. A visit that marked the start of an intensive artistic exchange.
There was a deeply felt connection between Jan Schoonhoven and Lothar Wolleh (Berlin, 1930–London, 1979). The two artists shared a deep interest in history and art and Schoonhoven loved to speak German.
Lothar Wolleh portrayed Schoonhoven on several occasions, and many of his portraits have now gained an iconic status. However, it was less known that Wolleh also photographed dozens of Jan Schoonhoven's reliefs; photos with a strong emphasis on the effect of light.
During several sessions at galleries, musea and the Schoonhoven's residence, but also in the open air in Delft, Lothar Wolleh photographed over 75 reliefs. These photos are of great value for art historical research, but they also bring us closer to what connected these two artists. In their search for a new imagery, Schoonhoven and Wolleh shared a deep-rooted fascination with the imaging properties of light.
Previoulsy unpublished photographs document an opening at Internationale Galerij OREZ, The Hague. The photographs are unmarked but were most likely taken at Schoonhoven's solo presentation at the gallery, 20 February-19 March 1971.
Many of such openings had live jazz performances. Anita Schoonhoven was a connoisseur and indefatigable promotor of jazz - we see her in the top image, far left.
Anita Schoonhoven began organizing jazz concerts in the mid-1960s, for which she succeeded in bringing international renowned musicians to the Netherlands. Jan Schoonhoven supported these concerts financially, as well as making awards - in the form of reliefs - for the annual Smør-djes Festival in Delft, an event also initiated by Anita Schoonhoven.
Selected exhibitions at Internationale Galerij OREZ, The Hague
'Decemberexpositie' (group) , 3–31 December 1960
'Sculpturen en Plastieken' (group), 15 December 1961–15 January 1962
'Nieuwe Tendenzen' (group), 18 January–10 February 1962
'Jan Schoonhoven' (solo), 13 March–15 April 1966 (parallel to a solo presentation of Armando)
'Jan Schoonhoven' (solo), 3 November–15 December 1967 (parallel to a solo presentation of Yayoi Kusama)
'Jan Schoonhoven' (solo), 4–23 April 1970
'Jan Schoonhoven' (solo), 20 February–19 March 1971 (parallel to a solo presentation of Nanda Vigo)
'Galerie m in Holland' (group), 5 November–21 December 1971
'Jan Schoonhoven' (solo), Galerie OREZ mobiel, 28 August–26 September 1981
'Tekenen' (solo) Galerie OREZ mobiel, 15 January–30 March 1990
How something white turned black, and then white again. Schoonhoven was not averse to experimentation. Sometimes with exceptional and unexpected results.
Since the late 1960s, Schoonhoven and artist-friend Jan Henderikse had been faithful correspondents, sending each other letters and postcards about life on their respective shores of the Atlantic Ocean – Henderikse moved to Curaçao in 1962, and to New York in 1967.
A letter to Henderikse from February 1979 offers the first sign that Schoonhoven’s work seems to have reached a turning point. After almost 20 years of monochrome white reliefs, there was room for experimentation:
"I’m now in the process of trying to make a couple of small black reliefs (coming close to Ad Reinhardt’s territory). Whether they’re any good remains to be seen." 
Since the late 1950s American artist Ad Reinhardt had painted grids and compositions based on crosses in shades of grey, dark blue and black, compositions that were exceptionally reductionist in character.
It is somewhat ironic that Schoonhoven referred to Reinhardt in particular. As early as 1953, in his essay ‘Twelve Rules for a New Academy’, Reinhardt had stated his aversity against the use of 'non-color' white in visual art:
"White is antiseptic and not artistic. It is appropriate and pleasing for kitchen fixtures, and hardly the medium for expressing truth and beauty." 
It is unclear whether Schoonhoven was aware of Reinhardt's essay, although in the case of the black relief, Reinhardt’s influence seems to have extended beyond the dark surface. Schoonhoven’s black (now white) relief R80-2 (1980) has the shape of a double cross, clearly related in form to Reinhardt’s compositions.
But the most striking thing Schoonhoven's letter appears to show, is that in 1979 he seemed no longer fully committed to the programmatic significance of the non-color white. And yet these doubts were short-lived, as history shows us.
Notes:  Jan Schoonhoven to Jan Henderikse, 7 February 1979, archives of Jan Henderikse, New York.  Ad Reinhardt, 'Twelve Rules for a New Academy', in: Kristine Stiles and Peter Selz (eds.), Theories and Documents of Contemporary Art. A Sourcebook of Artists' Writings (Berkeley/Los Angeles, 1998), p. 88.