"I don't believe the value will change... In a week or two this will be a distant memory," Ruarc Peffers told SAfm Market Update with Moneyweb.

He said the painting had become a celebrity in its own right and was politically interesting, but in five years time it would be "passé".

Barend la Grange and Louis Mabokela allegedly defaced the portrait with red and black paint at the Goodman Gallery in Johannesburg on Tuesday morning.

They were charged with malicious damage to property and were released on bail of R1 000 each.

The painting, titled The Spear, was part of Cape Town artist Brett Murray's exhibition Hail to the Thief II.

Peffers said it appeared that the paints used to deface the acrylic portrait were oil-based, which meant the painting could be cleaned.

"The red and black paint look oil-based.... If this is the case, then it wouldn't be too much trouble to remove," said Peffers.

"Theoretically, it can be cleaned."

The painting of Zuma has been widely condemned.

The ANC and Zuma have applied to have the controversial painting removed from the gallery on the grounds that it violates his and the party's dignity and rights.

It also wants the City Press newspaper to remove a photograph of the painting from its website.

The Freedom of Expression Institute (FXI) said on Wednesday that it supported the Goodman Gallery's refusal to remove the painting.

"We do not want to go back to a situation where art is censored because it offends the ruling party, or some take it upon themselves to dictate to others what is tasteful and acceptable," FXI said in a statement.

"We want to celebrate our artists, and not denigrate and control them in the way of apartheid, though they may provoke, push the boundaries and even cause offence."

FXI said it had been encouraged by the number of people who had derived a message from the painting.

However, it was also disappointed by the "excited" response by some, especially the ANC and its alliance partners.

"[They] have forgotten all those fine principles relating to freedom of expression and an open society for which so many fought. They misguidedly called for the picture's removal and even destruction," FXI said.