Precision optical flats ONLY!  No Liquids
You just add 2 drops of penetrating oil in the center of 1 disk and 2 drops ferrofluid in the center of the oil. gently set the other disk on top lightly press and counter rotate both disks to mix and blend.

Wipe off excess around edges.

DIY Supercell 52mm Optical Flats 2 Piece Set

Magnetic Field Viewer