SANDPAPER GRAIN 400 (DRY)

400 grit, the intermediate step a smooth surface rests on

400 is the value at which coarse work turns into fine. It is not suited to removing material, being too slow for that, but that is precisely why it leaves no scratches that would have to be laboriously smoothed out. Its job is different: to level the marks left by a coarser paper into an even matte on which you can tell whether a seam is really pressed shut or merely filled with dust. Without this intermediate step a defect appears only under the primer, when a repair is the most expensive.

Field of use

• Leveling sprue remnants after a part has been nipped from the frame
• Smoothing the parting seam after a fuselage or a hull has been glued
• Leveling dried filler flush with the surrounding surface
• Preparing the surface just before a coat of primer is applied
• Refining coarser marks where gloss varnish will end up

Dry sanding

This paper is built for work without water. Dry sanding has the advantage that you see at once how far you have got, because the dust falls into every unfilled scratch and gives it away. The disadvantage is clogging, so tap the paper out as you go and do not rely on it sanding the same way the whole time. Keep the pressure light and rather add to the number of strokes.

On flat areas run the strokes alternately crosswise, so that scratches from one direction cancel each other out. At edges and leading sections back the paper with a piece of hard rubber or plastic, otherwise your fingers will round the edge off. And above all keep to the order of grits; skipping a grade shows only after spraying, when the glossy layer emphasizes all the deeper scratches.