Got into a discussion with a client. She wants to repaint the interior walls and trim. For some reason she thinks the trim is painted with oil based paint. She went to Sherwin Williams to look for a color, and asked the guys there about repainting, they said you have to use oil over the old oil. Correct? Also, she asked how to tell the difference. They said the oil will chip, while latex will peel. Correct again?
Do it right, or do it twice.
Replies
Being a carpenter, I defer to my brother, the painter, on such matters. He agrees that unless you sand and prep and prime the oil based surface thoroughly, use oil based paint to cover oil based paint. And yes, usually latex will peel and oil will chip.
J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
I've used quality (SW) latex paints over old oil coats for many years and have never personally experienced a problem. And I've very rarely ever sanded or had to sand a surface. I've used TSP as a cleaning solution and followed with a liquid deglosser according to directions if the old coats are semi-gloss or gloss and had no problems. This means that you can't get too far out in front of yourself with the deglosser......maybe twenty minutes.
Knowledge is power, but only if applied in a timely fashion.
Edited 9/2/2003 11:34:44 AM ET by GOLDHILLER
I always get confused, as you can put one over the other, but not vice versa. I believe it's that you can put latex over oil (I know people use oil-based primers with latex top coats), but not oil over latex- I think the solvents screw up the latex underneath.
You definitely don't want to put latex over oil on exterior paints, or you'll get what happened on my house. The previous owner repainted and the new latex in some areas didn't bond to the oil and peeled off, most likely due to poor prep work. In others, however, it bonded too well, and the shrinkage and expansion of the latex broke the bond between the oil paint and the old wood siding. The paint peeled of in huge sheets. On the happy side, it's less for me to strip when I repaint!
I doubt you'll have a problem using latex over oil on interior trim if you perform the proper surface preparation, but the advantage of oil on trim is, in my opinion, fewer brush-marks, and better-looking trim.
Andy
You just made me realize that I should have clarified that I was talking about interior work only.
Agreed. No latex over oil on exterior work. Results will be exactly as you've described.
Now if you really want to see problems with mixing paints on exterior jobs……..
I've got one building over at the farm that suffered from this dilemma. My father
hired a fella back around '76 to paint the building which had always been
painted with oil. It only took about two years before the
problems began. We attributed the problem to poor prep and paint.
I went to repaint the building about five years later. My father tells me to use oil base as per normal. And so I did. About two years later, the paint is peeling in smallish sheets to the bare wood. I questioned my father whether he had any notion what might be causing this. That's when he remembered that the previous guy had drastically miscalculated how much paint would be involved but had a bunch of latex base with him and so just colored that on the spot to finish the other 3 sides of the building! Just great. Now we had a sandwich of oil-latex-oil.
In a word…….as you already know.......... not good. Don't do that. It took ALOT of work to get the building all back to bare wood. Ugh.
Knowledge is power, but only if applied in a timely fashion.
Edited 9/2/2003 9:39:53 PM ET by GOLDHILLER
Another easy on the spot check for latex is to use either goof off or denatured alcohol, alcohol being the quicker of the two. Put the alcohol on a rag and rub. If the paint starts to color the rag, it's latex. If you just get the dirt, it's oil.
"The child is grown / The dream is gone / And I have become / Comfortably numb " lyrics by Roger Waters
When I need to check oil or latex, I use Acetone. It takes off latex but not oil, quickly.
Sanding out is a good idea if, for nothing else, the quality of the surface.
When I need to transition from oil (bathroom, kitchens) to latex, I use Zinnser K&B paint. Good stuff, self priming, tintable to whatever you need. Saves a whole BUNCH of time.
Quality repairs for your home.
Aaron the Handyman
Vancouver, Canada
Is that the mildrew-proof Zinsser paint marketed under the name Perma-White ? While I have to agree that it will stick to just about anything and wears well; in my limited experiences with it, it just didn't produce a very good finish, especially when brushed..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
That's why, except for cutting in, I roll.Quality repairs for your home.
Aaron the HandymanVancouver, Canada
HI,
I read your entry with interest especially about using acetone to tell the difference between oil and latex paints. However I seem to have problems In sanding down old latex finishes,especually glossy finishes. The old latex paint comes away in little strips or balls, usually leving the surface in a worse condition. What is the technique to use in sanding latex finishes. Should I try wet sanding with wet and dry paper and water?
I appreciate any advice you can offer.
I lightly sand and never get balling up. Hmmmmm. Could be there was oil underneath and not enough adhesion.Quality repairs for your home.
Aaron the HandymanVancouver, Canada