Then all of the judges attended the gallery at 7am on Friday to decide the winners ahead of the midday announcement.
The Sulman prize - for the best subject painting, genre painting or mural project - is chosen by a single guest artist judge.
During the culling process, each portrait is brought before the judges and immediately placed in a No or Maybe category.
"It's a very solid weekend and it leaves everyone feeling quite tired - physically tired but also mentally tired because it's a concentrating job," Archibald curator Anne Ryan told AAP on Friday.
The portraits are moved around the walls of the gallery while the judges view them in different light guided by board president David Gonski.
"He keeps the process flowing but it's a consensus process," Ms Ryan said.
"Some judges will feel more strongly about some works than others but it's very open in that first round."
This year Ben Quilty and Khadim Ali were on hand to share their expertise as professional artists.
Ms Ryan said some years she has an inkling which portrait the judges will pick. But not in 2018.
"Yvette presented herself as a powerful, uncompromising, confident young woman but also she's positioned herself within a history of portraiture in this country."
"Self-portrait, after George Lambert" references the famous Australian painter and his portraits of contemporary women in the arts including Hera Roberts.
The increased number of self-portraits in the Archibald prize has been linked to the "selfie culture" but Ms Ryan doesn't think the two art forms have much in common.
"Selfies are fast and editable - you can take a lot of selfies and swipe most of them into the bin and it's very instantaneous."
"But portraiture, particularly self-portraiture, is slow. It's kind of the opposite of a selfie in a way."