Painting internal doors with natural wood pattern

It's a bit of a tough one to answer as you say 'paint' the doors. If the doors are of an embossed nature and have been painted a walnut colour then painting over should in most cases not take it the embossing, dependant on paint and costs of paint, if the door had been stained a walnut colour, over pine doors etc, then they tore off strain you use could cover the pattern you will need a light stain and you will need so give the door a light sand first. But from what im presuming, (which is something that really should not be done) is that it's just an embossed door that you have that had been painted, give the door a light sand, brush on the recommended undercoat, let dry, further sand and wipe away all dust then your good to go on the finish coat

Hi difficult to understand what you have from your description. Im guessing 2 versions. 1. Hollow panel doors with graining effect painted 'walnut color' Id advice a light sand and clean, then a water based paint system. Primer/undercoat then finish satin or gloss. 2. You have solid or veneered doors which have been stained and varnished. Same prep as above but use a super grip primer to begin with preferably from the zinsser range, if you dont it will chip off easily. As regards loss of grain effect, how thickly are you envisioning the paint is going to be applied?

Have you considered shelllac for your doors, it will keep the grain you want and provide a silky smooth finish once you have sanded and polished?

In common with many problems the answer can only be arrived at by reading the brief again carefully and by inspection. The pattern is the key. If it is the ripples in the moulding then paint should not reduce them if applied properly. If it’s the grain look that is required, then it is best not painted but stained or varnished. This could be clear, matt or with a sheen or with a thin colour like a bleach or limed look or a colour wash, thin to create the required match but leaving the grain visible.