Mercury in molds, for cleaning
Take heed that your mold be quite cold when you blow in order to get the ashes out. And afterwards put in ☿ in order to finish the cleaning. Because if the mold is hot, the ☿ will go inside; seek out the conduits in escaping, will leave its own odor, which will aggravate the tin or other metal that you will cast, such that it will break in touching the mold at all. The heat of the mold also retains some little grains of ☿ that will make lumps; stick to the sides of the molded leaves and attach to them; make them frangible. The ☿ cleans ashes well. Likewise flat things where there are not delicate traces that it could break with its weight. And therefore, if you can cast neatly without putting it in, don’t use it at all. But if you have need of it, mix your crocum sand so that it withstands fire well. And after having put in the ☿, evacuate it, bouncing the end of the mold from below while moving it. Afterwards reheat your mold gently so that the ☿ is gone from everywhere. In this way I cast a branch of periwinkle leaves; flowers very neatly. Having put a branch of melted [illeg] in the flower, on the back of the flower [illeg].
at left bottom margin of folio 158r
Reheat your mold until it is good and red before casting, so that the ☿ evaporates well.