Our front door has a dark stain on it and then a thin layer of varnish. I would like to paint the exterior side a black gloss and the interior a satin white. Do i have to do anything to the door before painting other than sanding it down? I am particularly concerned about the stain bleeding through on the white side, will I need a primer?
As Rosebery has suggested Zinsser bulls eye, brilliant product but be aware there are three types, a solvent based, a spirit based, and water based. I personally would use the water based one. We don’t know if the door was stained originally with a spirit based stain or an oil based stain. The water based sinister will seal the oil based stain and the top coat would seal the spirit based stain if it bleeds through. Prep your door well and apply 2 cts this can be tinted to a grey with a universal tinter for the black side, then finish with an oil based gloss.