At last, I’m up to the actual mulberrying stage. All the show wood was given a final wash down with hot water to remove any grime and glue residue before liberally wiping it over with aqua fortis (nitric acid).
When the wood was thoroughly dry, I brushed it over with a mixture of boiled linseed oil and lamp black per Stalker & Parker’s recommendation. I allowed the black oil to soak in for about five minutes and then wiped off the surplus.
The oil will be left to dry for about two days before proceeding.
 John Stalker & George Parker, A Treatise of Japanning and Varnishing, Oxford, 1668.