Why after painting the interior of the house with oil based paint, it shows patches? Or un-even shades?

Question

Actually the colour of the paint was white and we just re-painted the old oil based paint which was also white..

Answer 1

Did you sand the patches and prime the walls a couple of times before you painted?  Unless you have a perfect wall under your final paint job, Using oil based paint will highlight any imperfections.

Answer 2

The previous answers cover the prep well.....on the painting itself......Paint so you are touching the previous still-wet surface.   reroll each strip and most of the previous one.  work fast and evenly.    It is often helpful to paint one light coating first and repaint within the time frame indicated on the paint can so you won't have to do any additional adhesion preparations.

Answer 3

Oil based paints especially colored paint other than white will show any imperfection in the wall if it has been patched and not sanded down perfectly smooth about the only way to fix this after painting is to get some drywall mud and go over the areas again and feather it out then re sand it and make sure it is perfectly smooth before painting it again.

Unfortunately this is the best way to fix it.

Answer 4

The first problem  I'd suspect would be improper preparation of the surface, particularly regarding priming. Any portions of the wall that were patched, spackled, or had bare drywall (or plaster) should be primed. Otherwise the paint will look different on these surfaces.

The other issue may simply be poor coverage. If you didn't provide a good enough first coat, a second coat may help to even out the look. Also, some paints just don't hide as well as others, which means that two coats are often required, particularly if you're painting over dark colors with light colors.

Here's an article "Secrets of the Pro Painters" that will give you some tips on surface prep and painting technique:

http://www.thisoldhouse.com/toh/article/...