User instructions for the liquid hard ground Johnson Klar floor polish:

For a hard ground, we use an acrylic floor polish. The liquid hard ground is extremely strong, and the plate can be wiped and printed while the hard ground is still on. You can work in the acrylic hard ground in exactly the same way as in the conventional hard ground, but you also have the option of doing washings in the hard ground with a mild solution of ammonia and water.

• Hold the plate above the tray and pour on a liberal amount of the hards ground in one go.
• Quickly distribute it (before it has time to harden) and immediately place it in a vertical position on a newspaper to let the excess polish run off.
• Move the plate a few times on the newspaper to prevent the hard ground from building up along the lower edge. A thin, even coat of hard ground is essential: otherwise, it will break up when etched.
• After a few minutes on the newspaper, the plate is ready to be hardened in the drying cabinet. After 10 minutes of hardening, the surface is ready to be worked.
• On a copper plate, the hard ground will now be ready for use. A zinc plate will require another thin coat of floor polish (as described above) with a drying period of five to ten minutes, after which the plate will be ready.
• The liquid hard ground in itself forms a complete clear (transparent) surface, but if you prefer a black surface (like the old-fashioned smoked plate) spray or paint it with diluted black gouache. (paint=1 part water, 1 part gouache; spray= 2 parts water, 1 part gouache). Lascaux Studio 972 black (acryl) can also be used for this purpose.
• The gouache or Lascaux black dries in the drying cabinet in a few minutes.
• Before etching, remove the ink layer with a soft sponge with lukewarm water and detergent, in order not to spoil the ferric chloride. The Lascaux can be left on during etching.

Materials:
Hard Grond: Johnson Klear Polish, or Future Floor Polish, or Z*Acryl Hardground
Washing: Ammonia and water, or soda and water
Black colour: Black Gouache, or Lascaux Studio black 972.

Text Henrik Boegh, Artguide.