# Room painting question **URL:** \ **Category:** Factual Questions\ **Created:** [February 20, 2010, 1:22pm UTC](https://boards.straightdope.com/t/room-painting-question/529762 "2010-02-20T13:22:19Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [February 20, 2010, 1:22pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/1 "2010-02-20T13:22:19Z")
Is there any reason why I shouldn’t paint a room with latex paint, if the previous paint was oil-based? Both are flat. Back when I was in art school, we were taught that when doing an oil painting, you should always paint “fat over lean,” meaning a layer containing more oil should be over a layer with less oil. Does that same principle apply to wall painting? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [February 20, 2010, 3:11pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/2 "2010-02-20T15:11:29Z")
Latex over oil used to be “a bad idea”, but that was long ago. I think all major brands of latex are OK with it now, but your best bet is to check the cans of paint at the store. They will say. If you want a particular brand for some reason, and they recommend against it, you can get a primer paint. The most important thing is to follow the directions for surface preparation, especially making sure the walls are clean of grease. They’ll probably recommend using TSP, but we’ve just used spic 'n span with good results. ---
**Author:** ![kayT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayt/32/3633_2.png) [@kayT](https://boards.straightdope.com/u/kayT)\ **Post date:** [February 20, 2010, 4:49pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/3 "2010-02-20T16:49:03Z")
I used a latex paint over oil and the paint said it would be fine. And it was, eventually. However, it took nearly three weeks to get completely dry, as in things not sticking to it. This was a problem as it was a built-in shelf unit and I could not put anything on it for that time. So be ready for a loooooong drying time. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [February 20, 2010, 6:49pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/4 "2010-02-20T18:49:46Z")
> [@ZenBeam](#): > > Latex over oil used to be “a bad idea”, but that was long ago. I think all major brands of latex are OK with it now, but your best bet is to check the cans of paint at the store. They will say. If you want a particular brand for some reason, and they recommend against it, you can get a primer paint. > > The most important thing is to follow the directions for surface preparation, especially making sure the walls are clean of grease. They’ll probably recommend using TSP, but we’ve just used spic 'n span with good results. TSP is the main ingredient in Spic’n’Span. **panache45** , as long as the old paint is in good shape, you should be fine with cleaning and sanding, then applying a 100% acrylic latex paint. Primer should not be necessary unless you need to suppress mildew or something, or radically change colors, or because you’re married to some paint that’s not going to work (as **ZebBeam** said). If the old paint is not in good shape, you need to strip it (at least the bad parts). You should do this anyway, but latex paint makes it imperative. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [February 20, 2010, 7:29pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/5 "2010-02-20T19:29:01Z")
> [@Nametag](#): > > TSP is the main ingredient in Spic’n’Span. Not in my box, and not in any of the _Spic and Span_ listed [here](http://www.spicnspan.com/msds.htm). Maybe it [used to be in there](http://en.wikipedia.org/wiki/Trisodium_phosphate#Cleaning): > [@](#): > > By the end of the 20th century, many products that formerly contained TSP are now manufactured with TSP Substitutes, which consist mainly of sodium carbonate […] ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [February 20, 2010, 7:31pm UTC](https://boards.straightdope.com/t/room-painting-question/529762/6 "2010-02-20T19:31:39Z")
> [@kayT](#): > > I used a latex paint over oil and the paint said it would be fine. And it was, eventually. However, it took nearly three weeks to get completely dry, as in things not sticking to it. This was a problem as it was a built-in shelf unit and I could not put anything on it for that time. So be ready for a loooooong drying time. Sounds like that [doesn’t have anything](http://www.woodweb.com/knowledge_base/Latex_Paint__Too_Soft_for_Bookcases.html) to do with the oil paint. ---
**Author:** ![kayT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayt/32/3633_2.png) [@kayT](https://boards.straightdope.com/u/kayT)\ **Post date:** [February 22, 2010, 5:45am UTC](https://boards.straightdope.com/t/room-painting-question/529762/7 "2010-02-22T05:45:44Z")
Wow, who knew? But what do I get? There’s no oil paint around is there?