Profil „H“ 3,2 mm

The stronger H, section 3.2 mm

A markedly more robust size in the same range. A 3.2 mm section will carry the role of a purlin under the roof of a lean-to or of the frame of entrance gates without sagging under its own length. The material is white polystyrene; the rod is 35 cm long and is sold singly.

What corrosion really looks like

Rust never covers a surface evenly. It arises where water stands: in corners, under rivets, on the lower edge and in the gap where two parts touch. The tone meanwhile shifts from dark brown at the core of the stain through ocher to orange at the perimeter, and a fresh bloom is always deeper than one years old. A beam painted a continuous orange looks painted, not corroded.

The order that gets results

• Darken the base toward brown so that it shows through from below.
• Form the stains by stippling with a frayed brush, never with a stroke.
• Settle dry pigment with a drop of thinner applied beside the stain.
• Lead the run marks vertically down from the source of the corrosion.

On smooth plastic the reverse procedure also proves itself. First the rusty areas are laid down, over them comes the shade of the top coat, and that is wiped away in places with a cotton swab while still wet. Exactly those areas that are meant to be bare are revealed underneath, and the transition comes out softer than any brushwork. The method is sensitive to timing, though: once the top layer has dried, it no longer gives and all that is left is to sand.

Keep the offcuts too. Short pieces serve as spacers between walls, and when testing a shade you can check the paint on them without risk.