End-grain wood is the wood that shows the growth rings of the tree. This area has a tendency to absorb paint, so it must be primed prior to painting. If it isn't primed, the porous wood grains will soak up the paint and alter the paint lustre or colour. End of grain wood is commonly found at the ends of boards, but is also found in the wood knots of a board. Unfinished end-grain wood is rough, and needs to be sanded before paint is applied.
Dip the putty knife into the tub of wood putty and dig out a thumb-size portion of putty.
Press the putty into the end-grain wood cracks, using the putty knife's broadside. Scrape off excess putty with the tip of the knife until the putty is as smooth as possible. Apply as much putty as is needed to fill all of the cracks. Allow the putty to dry for 24 hours.
Sand the dried wood putty smooth with a 120-grit sanding block. Vacuum up all of the dust.
Open the stain-blocking wood primer. Dip the paintbrush into the primer and prime the end grain wood and the wood putty. Allow the primer to dry 24 hours, then apply a second coat. Wait 24 hours, then paint over the primer with a coat of wood finish paint.
Roll over the brush marks with a mini roller in necessary.
If you fail to use a stain-blocking primer, the sap in the end wood grains may bleed through the finish paint.