Use the correct type and grit sand paper
Thorough sanding is required to ensure optimum mechanical adhesion and to create a smooth finish. Bare surfaces, primers, undercoats and fillers need to be dry sanded in order to avoid the absorption of moisture.
Sanding between fresh topcoats and varnishes can best be executed with a fine grit wetordry sandpaper and water. For every surface use the correct sanding paper and grit.
Avoid mechanically sanding in combination with coarse sandpaper as this causes too rough sand marks. Also too much film thickness is being sanded down and consequently sufficient film build-up will not be achieved. After sanding remove all dust and degrease once more.
TIP: Sand bare wood along the wood grain. Always sand fresh varnish layers by hand with a fine grit wetordry sanding paper and water.
Sanding bare surfaces P-Grit
Bare GRP/fiberglass 320-360 dry
Bare steel 60 dry
Bare wood 180-220 dry
Existing paint/varnish layers 220-320 dry
Sanding painted surfaces P-Grit
One-component primer coats 220-320 dry
Two-component primer coats 180-220 dry
Fresh one-component topcoats 400-600 wet
Fresh Twocomponent PU topcoats 320-360 wet