He was highly regarded by Philip, and undertook a number of diplomatic visits abroad, including to Lisbon in 1428 to explore the possibility of a marriage contract between the duke and Isabella of Portugal.

Ten are dated and signed with a variation of his motto ALS ICH KAN (As I (Eyck) can), a pun on his name, which he typically painted in Greek characters.

[14] Over the following decade van Eyck's reputation and technical ability grew, mostly from his innovative approaches towards the handling and manipulating of oil paint.

His motto, one of the first and still most distinctive signatures in art history, ALS ICH KAN ("AS I CAN"), a pun on his name,[17] first appeared in 1433 on Portrait of a Man in a Turban, which can be seen as indicative of his emerging self-confidence at the time.

[19] Van Eyck undertook a number of journeys on Philip the Duke of Burgundy's behalf between 1426 and 1429, described in records as "secret" commissions, for which he was paid multiples of his annual salary.

Started sometime before 1426 and completed by 1432, the polyptych is seen as representing "the final conquest of reality in the North", differing from the great works of the Early Renaissance in Italy by virtue of its willingness to forgo classical idealisation in favor of the faithful observation of nature.

Telltale signs are hinges on original frames, the sitter's orientation, and praying hands or the inclusion of iconographical elements in an otherwise seemingly secular portrait.

She is typically seated, wearing a jewel-studded crown, cradling a playful child Christ who gazes at her and grips the hem of her dress in a manner that recalls the 13th-century Byzantine tradition of the Eleusa icon (Virgin of Tenderness).

Her monumental stature borrows from the works of 12th- and 13th-century Italian artists such as Cimabue and Giotto, who in turn reflect a tradition reaching back to an Italo-Byzantine type and emphasises her identification with the cathedral itself.

Art historians in the 19th century thought the work was executed early in van Eyck's career and attributed her scale as the mistake of a relatively immature painter.

Many of van Eyck's religious works contain a reduced interior space that is nonetheless subtly managed and arranged to convey a sense of intimacy without feeling constricted.

This can be seen from the many examples of features that would be unlikely in a contemporary church, including the placing of a round arched triforium above a pointed colonnade in the Berlin work.

The lettering on the arched throne above Mary in the Ghent Altarpiece is taken from a passage from the Book of Wisdom (7:29): "She is more beautiful than the sun and the army of the stars; compared to the light she is superior.

[32] Wording from the same source on the hem of her robe, on the frame of Madonna in the Church and on her dress in Virgin and Child with Canon van der Paele, reads EST ENIM HAEC SPECIOSIOR SOLE ET SUPER OMNEM STELLARUM DISPOSITIONEM.

They breathe life into portraits and give voice to those venerating Mary but also play a functional role; given that contemporary religious works were commissioned for private devotion, the inscriptions may have been intended to be read as an incantation or personalized indulgence prayers.

[21] Van Eyck's portraits are characterized by his manipulation of oil paint and meticulous attention to detail; his keen powers of observation and his tendency to apply layers of thin translucent glazes to create intensity of color and tone.

It evidences many of the elements that were to become standard in his portraiture style, including the three-quarters view (a type he revived from antiquity which soon spread across Europe),[18] directional lighting,[21] elaborate headdress, and for the single portraits, the framing of the figure within an undefined narrow space, set against a flat black background.

[50] Notes made on the reverse of his paper study for the Portrait of Cardinal Niccolò Albergati provide insight into Eyck's approach to minute detailing of his sitter' faces.

[51] Even in his early works, his descriptions of the model are not faithful reproductions; parts of the sitters face or form were altered to either present a better composition or fit an ideal.

[62] His use of symbolism and biblical references is characteristic of his work,[62] a handling of religious iconography he pioneered, with his innovations taken up and developed by van der Weyden, Memling and Christus.

[65] To him the day-to-day is harmoniously steeped in symbolism, such that, according to Harbison, "descriptive data were rearranged ... so that they illustrated not earthly existence but what he considered supernatural truth.

"[65] This blend of the earthly and heavenly evidences van Eyck's belief that the "essential truth of Christian doctrine" can be found in "the marriage of secular and sacred worlds, of reality and symbol".

[66] He depicts overly large Madonnas, whose unrealistic size shows the separation between the heavenly from earthly, but placed them in everyday settings such as churches, domestic chambers or seated with court officials.

[67] Van Eyck's iconography is often so densely and intricately layered that a work has to be viewed multiple times before even the most obvious meaning of an element is apparent.

The symbols were often subtly woven into the paintings so that they only became apparent after close and repeated viewing,[62] while much of the iconography reflects the idea that, according to John Ward, there is a "promised passage from sin and death to salvation and rebirth".

[72] The words may be related to a type of formula of modesty sometimes seen in medieval literature, where the writer prefaces his work with an apology for a lack of perfection,[72] although, given the typical lavishness of the signatures and mottos, it may merely be a playful reference.

"[18] By contrast the inscriptions on his public, formal religious commissions are written from the point of view of the patron, and there to underscore his piousness, charity and dedication to the saint who he is shown accompanying.

Pieces such as the Dresden Triptych were usually commissioned for private devotion, and van Eyck would have expected the viewer to contemplate text and imagery in unison.

The texts are drawn from a variety of sources, in the central frames from biblical descriptions of the assumption, while the inner wings are lined with fragments of prayers dedicated to saints Michael and Catherine.

It is thought that van Eyck died leaving the panel unfinished but with completed underdrawings, and the upper area was finished by workshop members or followers.