Although Willumsen worked with many different visual artistic expressions, painting was his preferred medium. He painted throughout his life, and paintings constitute by far the largest part of his production. In their thematic and formal range from period to period, they reflect the vastly different painterly problems he worked with.

In the 880s, his years of apprenticeship, he painted in the spirit of naturalism with a social commitment, as did several of his peers. Willumsen painted portraits of models, scenes from his travels in Denmark, and in 1888 The Wedding of the King's Son, which had a clear social purpose.

Breakthrough in the late 1880s

He had his real breakthrough as a painter in 889, when he spent his first trip abroad in Spain and Paris. The colour became full of light, and the motifs took on surprising cuts and angles of view. In Winter Day on Montmartre (National Museum of Art) one looks diagonally up a paved road, and in Street Going Down in Alora (David's Collection, deposited in the Hirschsprung Collection) the light shines from the falling street.

1890s

During his next stay in Paris in 890 and the following years, he produced several symbolist paintings with a simplification that particularly emphasized the movement motif. He wanted to depict some realities rather than give a picture of a momentary mood. In descriptive texts in exhibition catalogues, he sought to emphasize the often somewhat speculative content. It was the demand of symbolism that the ideas should have a visible form in a symbolic language. And Willumsen used the simplification of symbolism with a decorative surface treatment without details.

After the turn of the century

After the turn of the century, Willumsen took up completely new subjects in a new form. In a series of monumental expressionist paintings, he depicted the relationship between man and nature. The individual was pitted against the forces of nature, and the general cult of the body at the time was emphasized. In A Mountaineer from both 1904 – Hagemanns Kollegium, Copenhagen – and 1912 – Statens Museum for Kunst – a free woman who hikes mountains draws strength and energy from nature, liberated by Willumsen's perception of nature and experiences in the mountains. In the paintings Bathing children on Skagen's beach from 1909 and Nature's Fear. After the storm no. 2 from 1916, he shows nature from diametrically opposite sides.

1910s

In the following decade, Willumsen's travels in the Mediterranean countries became of great importance, together with his studies of the paintings of the Greek-Spanish artist El Greco (1541-1614). The colors become stronger and more intense, and a number of folk scenes are painted with pure, clear colors. In the portraits from these years, the color is driven up so high that it has consequences for the mood, as is the case in Aftensuppen from 1918, where a very dramatic and intense atmosphere prevails. During the First World War, Willumsen settled in the South of France, where he remained for the rest of his life.

1920s

In the 1920s, Willumsen was busy completing The Great Relief, which was commissioned by the Danish state on the occasion of his 60th birthday in 1923. The relief was installed at the National Gallery of Denmark in 1928, but has been permanently deposited at the JF Willumsen Museum since 1957. However, Willumsen also produced other interesting works during these years, including The Painter Receives the Musician and Art Historian Vilhelm Wanscher, both theorized in 1923.

The trilogy – a picturesque testament

In addition, in the second half of this decade Willumsen painted a series of three large self-portraits, the Trilogy of Dying Titian, which was intended to give posterity a picture of him as a significant artist. As in most of the self-portraits, he examined his self-created mythical position as an artist.

The crooked Willumsen

In his late old age, he still painted large pictures, and his muse, Michelle Bourret, was often the model. Sometimes she helped with the actual painting.

The largest work that Willumsen did as a sculptor was The Great Relief, which he began in 1893 and completed in 1928. It occupied his time for long periods, and he imagined a work that he could show at exhibitions in Europe. It was his intention to express something universal about life and existence. He struggled to materialize his thoughts, but unfortunately he did not get the relief done in the 1890s, when he was passionate about it. Only later was it created in marble in a rougher version.

Grave monuments

Most of the other sculptural works Willumsen carried out were commissioned. He made several funerary monuments of widely varying character. For his own parents two colossal heads (Vestre Kirkegård), as he had used in Det store Relief, for Agnete Pontoppidan (Holmens Kirkegård) a woman lying on the ground, and for the doctor and physiologist Christian Bohr (Assistens Kirkegård) a tense sculptural form with an owl placed asymmetrically. In the draft for a double sarcophagus for Christian IX and Queen Louise in Roskilde Cathedral he worked in accordance with Wiedewelt's existing interior.

The Hørup Monument

At the Hørup Monument and the Ravens at the Open Air Theatre, he created sculptures that were effective from all sides and were created for the purpose and the surroundings.

In several portraits Willumsen tried to create something special, but without much success. He had the marble works carved by professionals; only A Physiologist and the portrait of Elisabeth Dons were carved by him himself.

Even if Willumsen had only been a graphic artist, his production would be fully sufficient for a significant placement. He has produced etchings, lithographs and woodcuts, and within each technique he has exploited its special qualities.

The etchings fall into two distinct periods, the first from 1885 to 1891 and the second from 1916 onwards. In the first period he produces realistic scenes and later leaves with motifs from Copenhagen, in which he highlights features of the city and its inhabitants. The unkind reception of Frugtbarhed in 1891 led him to put the etching away.

Etchings – World War I

Inflamed by the horrors of World War I, he produced several strong etchings with motifs from the theater of war. The dramatic effects of the etchings were adequate for the gripping scenes. Alongside the depiction of the horrors of war, he used the same effective technique to depict oddities he had met in southern European countries. They were never given away in the depiction, but presented with an understanding humor.

Lithographs

In lithography, Willumsen produced several posters that advertised the Free Exhibition and his own studio exhibition with monumentality. From 1910 he produced a series of lithographs with completely different motifs than the subjects of the etchings. The joys of home life were reproduced in lines, where he could quickly capture snapshots. Some travel motifs are also lithographed with a light line effect.

Woodcut

Willumsen only started woodcuts late, which he often used for portraits. Perhaps this technique corresponded to the perception he had gradually formed of other people in his somewhat isolated life. The figures are built up from the small, sharp strokes that are characteristic of the hardness of the wood.

Especially with the etchings, Willumsen worked with many changes within the individual sheet. With proofs and many different conditions, he persisted until a satisfactory result was achieved. By working carefully with the technical side of the matter, he achieved astonishing results that were rarely accidental.

Willumsen as a ceramist

In the almost ten years Willumsen worked with ceramics, he managed to create several monumental works and act as artistic director for the porcelain factory Bing & Grøndahl. In 1891, when his first child was born, he created the colorful Family Vase (Museum of Fine Arts). A peculiar work full of emotions and difficult to interpret symbols.

In the following years he experimented with glazes, which were used on vases and the colossal heads for the Great Relief. In a smaller format he executed the Girl in Pants in different colours, which was intended to be used on the side of the relief that caused him the most problems.

In both Paris and Copenhagen he had built his own kilns, where he fired the majority of his ceramic works. In two notebooks he had carefully copied down glaze recipes and added notes on how the firing had proceeded.

During the few years he was employed at Bing & Grøndahl, he acted as a mentor to other artists, and when the coveted first prize was won at the World Exhibition in Paris in 1900, he left the factory. He set off for America, where he hoped to make a career as an artist.

Two periods

His production as a ceramist can be divided into two temporally distinct periods. In the early 1890s, in Paris, he attempted to create free ceramics with a symbolic content. He experimented with human representations in special designs.

Technically, however, he had some difficulties that destroyed several works. It was not until 1896, when he had obtained a large kiln in Copenhagen, that he was able to master several of the technical problems. He now concentrated mostly on glaze experiments and vases, ash urns and the completion of The Great Relief.

When Willumsen bought a camera during his visit to the World's Fair in Chicago in 1893, he began using it immediately. He photographed the skyscrapers, and later he took pictures on his many travels. The mountains in particular fascinated him, and he sought to capture different moods with sun and clouds and light and shadow.

In many of his photographs he worked with the same problems as in his paintings. In Paris and Copenhagen, for example, he made many recordings of people in motion. This was especially the case in the 1890s, when the motif of movement was also prevalent in his paintings and graphics.

He has made photographs that have been used as models for the paintings, and photographs that have meaning and value in themselves. He has often photographed his loved ones and made arrangements in which he carefully arranged the motif. In the many photographed self-portraits, he has repeatedly staged himself and placed great emphasis on how he appeared.

Unlike his works in other genres, Willumsen never had the photographs exhibited.