This shot is from the Rietveld collection in a museum if I remember. I have tried two types Liquid Emulsion (there are much more) Black Magic and Foma photo emulsion. Both are good. The wood is varnished with alkyd varnish first. (Gandolfi did explaine more here, many thanks Gandolfi !!!) http://www.apug.org/gallery1/showimage.php?i=73117&c=2