Iron filings.

Both are synthetic-resin based and waterproof once dry, but they do different jobs. Final Varnish is very fluid, dries transparent and satin matte, and its UV protection guards the colors against yellowing and fading. Acrylic adhesive is creamy, dries clear and glossy, and binds: use it to mix texture pastes with Gray Stone Powder, build rust surfaces with iron filings or glue collages.

Brush it onto the finished painting as the very last step. Several thin coats are better than one thick one. Final Varnish protects your work and at the same time fixes texture materials and fillers. Acrylic adhesive can also be used as a varnish: dilute it 1:1 with water and stir well.

With Gray Stone Powder, a finely ground natural limestone from Vorarlberg, and a binder. Acrylic adhesive and Gray Stone Powder in a 1:3 ratio give a creamy paste that hardly cracks, for example for rock and concrete looks. White Chalk Paint and Gray Stone Powder in a 1:2 ratio dry matte and form cracks. Gray Stone Powder will not hold without a binder: if you sprinkle it loosely onto wet paint, tap off the excess once dry and reuse it.

In two steps. First, iron goes onto the ground: brush on liquid iron neat or diluted for smooth rust surfaces without grain. Iron filings are sprinkled into a still-damp base of acrylic adhesive, Acrylic Paint, Chalk Paint or Modeling Paste, and they bring coarse texture. Then spray the oxidizing agent as a fine mist onto the damp or dry surface, thoroughly but without puddles. The first rust tones appear after about one to two hours; for more intensity, simply spray again.

Yes. Varnish can darken the rust surface slightly, though, which can intensify or change the effect. So test it on a small area first, and only seal once the rust has reached the tone you want and has dried through. Many artists deliberately leave real rust unsealed. It then keeps working slowly and can darken further.

For rust effects with liquid iron, iron filings and oxidizing agent, we recommend gloves and a protective underlay, plus a respirator for large areas. You can find the safety data sheets for liquid iron, oxidizing agent, Gray Stone Powder, acrylic adhesive and Final Varnish (still listed there as Acrylfirnis) as PDFs on our downloads page.