At the Herod exhibit at the Israel museum there is a room that is a reconstruction of the loggia, the VIP box from the Herodium theater with its colorful panels on the lower part of the wall and above on light-colored plaster, unique paintings in secco, trompe de l’oeil views through an open window. Secco is a technique that requires less artisan skill and used when time is short as in the approaching visit of Marcus Aggripa in 15 BCE. In secco paint is applied on top of dry plaster whereas in fresco the paint is added while the plaster is still wet. The fresco technique requires skilled craftsmen who have to work applying small areas of plaster, smoothing it and then adding the mineral pigments.
The loggia at Herodium is not accessible to the public, room is enclosed by a wooden structure and a team of conservators are working to protect the delicate secco painting. Last week while guiding at Herodium I found the door open and was able to look in for a moment. Hence the photos below were taken in a rush, using my iPhone - since few images of the loggia have been shared I offer them for viewing here.
Two things struck me: 1) Through holes in the plaster you can see that the lower panels have two layers of paint and plaster implying that the walls were redecorated, probably for Marcus Aggripa’s visit. In talking to Dudi Mevorah, curator at the Israel museum, the outer layer is not fresco but a covering done in secco.
2) There are delicate paintings still on the upper section of the wall that are being conserved in place. The painting on display in the museum exhibit is a painstaking reconstruction of thousand of tiny pieces of paint found on the floor of the loggia by museum staff. You can view it at http://israeltours.files.wordpress.com/2013/02/secco-loggia.jpg