Hammacher attaches great importance to a scholarly opening up of the collection and is surprised that there is little attention for this in the Dutch museums. According to him, the Rijksmuseum Kröller-Müller also ‘has very little to offer […] in the way of catalogues, publications, images. Opportunities to study, also for foreigners, who want to see the unexhibited section, did not and do not exist’. In 1951 he appoints Ellen Joosten, a Master in Dutch linguistics, as his scholarly assistant. Joosten is instructed to ‘make [the collection] public through detailed catalogues’. In late 1952, the first catalogue dedicated entirely to sculpture is published, in which 310 sculptures are described, from Helene’s Asian Buddhas to Hammacher’s latest acquisitions.

The cover of Catalogus verzameling Rijksmuseum Kröller-Müller: Beeldhouwwerken (Catalogue collection Rijksmuseum Kröller-Müller: Sculpture) is adorned with a print of Squatting woman by Rodin, photographed by head technical assistant Martinus van den Brink, who has worked for the Kröllers since the 1930s.

From the outset, Hammacher is committed to resuming construction of the new wing, which was halted during the war. The promised financing from the State, however, is long overdue. He eventually turns to the press to draw attention to the problem. The media supports him with the headline: ‘Why is there still no extension for the unique Kröller-Müller Museum?’ This is effective. In 1951, with help from the Marshall Plan, work on construction of the new wing can finally resume.

The new extension has 5 spaces for painting, 2 print rooms, an auditorium with 350 seats and a large gallery for the sculpture collection. Hammacher wants an exhibition space that can ‘enhance the spatial and light effects on sculptures’. Adjoining the existing space that has hardly any windows, Van de Velde designs a sculpture gallery with two walls made entirely of glass, to allow ‘as much nature as possible’ to enter. In Van de Velde’s plans, tracery would be applied to the windows. Hammacher is convinced that the tracery would disturb the viewing of the sculptures and manages to persuade the architect with photographs of a test setup. The windows are produced without tracery.

Hammacher wants to use the new auditorium to make the museum ‘a centre of activities’, where ‘the spirit can be awakened, guided and grown’. With this approach, he already organizes concerts and chamber music evenings, which are well attended.

Van de Velde realizes that with the completion of the new wing, the ‘Grand Museum’ will never materialize. From his home in Oberägeri, Switzerland he focuses entirely on the extension plan and monitors the completion of every detail. In 1953, the then 90-year-old architect makes his final visit to Otterlo. However, he does not wish to see the foundations of the ‘Grand Museum’, as this would be too upsetting for him.

In the sculpture gallery, Hammacher installs the new acquisitions of Rodin, Zadkine and Arp, and 3 sculptures from the existing collection: Standing female figure by Lehmbruck, Madonna and child by Rädecker and Bather with raised arms by Maillol. A tapestry designed by Fernand Léger is also hung in the sculpture gallery. The ‘exquisitely powerful work’ is an integrated component of the architecture and marks the entrance to the painting collection in the old part of the museum. A place of honour is reserved for Maillol’s bronze sculpture Kneeling girl, which Van de Velde donated to the museum the previous year.

The red tiles on the floor are laid in a pattern designed by the architect Gerrit Willem Baas. He was already involved in the construction of the museum in 1937 and is now again responsible for the finishing at the special request of Henry van de Velde. The new wing – with the exception of the auditorium which is not yet ready – is opened to the public on 23 April 1953.