Fluxes for traditional tinning (wipe tinning)

Hi. I am a research student working on tinning practices in antiquity.
In literature is mentioned that rosin was used as a flux on the low tin bronze substrate prior to application of the tin.
I would much appreciate if you could point out a practical guide on this, or if you could share your practical experience on the subject, especially in relation to the use of flux.

Instead of rosin you can use lard(or any other animal fat),or oil mixed with fresh coniferous wood pitch.Copper must be oxide free.Do not overheat(tin is metal which can be melted very easy ).Try internet archive website-there you can find some old books on copperwork(all download free-www.archive.org).Hope it helps and good luck!