Oil, Latex, why does this matter?
Oil and latex based paints are polar opposites of each other, and because of this there are some things that latex based paints are better at than oil and vice versa. Additionally before you begin painting you will need to know what kind of material you are painting over so that you do not have your job fail. In this article I will tell you in what situation it is a good idea to use each product and where it should be used. This article will also help you determine which finish you currently have on your project so that you can paint over it with the correct material.
How do I know which product I am painting over?
This is a very important question and one that should be answered before you even start your project. A painter who knows what he or she is doing can tell often just by looking at the surface weather it is oil or latex based. For someone who is not a painter however, there are a few things that you can look for that will be dead giveaways as to weather you are dealing with oil or latex. First if you know that the surface has not been painted in over a year try to find an area where the paint is subject to total darkness. Oil based paint will yellow over time when subject to low light conditions. For instance if you are painting the door trim in your home, look at the trim of a door inside a closet. It would be an indication that you have an oil base material on your trim if the inside of the trim has yellowed compared with the outside. You can also look for this yellowing on the inside of a cabinet door or on a base board that was blocked by a bed or a dresser. This trick will be more apparent if you your trim is a lighter color and will be less effective if looking at a darker color or a color already painted yellow.
If you checked for yellowing, but still feel unsure as to what material you currently have on your project there is one other thing you can do which which can definitively tell you which material you have. Get some denatured alcohol from your paint or hardware store and in an inconspicuous place take a q-tip with alcohol on it and rub the surface. If the paint rubs off with the q-tip, you have a water based material on your surface. If the material does not rub off then odds are you have an oil based material. These tricks will work 99% of the time, but there are a few finishes that could give you a false indicator as to what material was used. Contact a professional if you are ever unsure, as using the wrong products could result in a failure of the finish you put on! For instance if you are looking to paint your kitchen cabinets and used the alcohol to try to determine the finish, you could be fooled into thinking you have an oil finish when in fact you actually have something more exotic such as a conversion varnish. Never ever paint cabinets in latex, and should you already have it on your cabinets… My condolences.
Whats the difference?
The first obvious difference you will notice about each product right off the bat is the smell. Oil based materials will smell A LOT stronger than your latex based materials. With that said, if you are a person who makes a big deal out of each chemical that enters your olfactory, you may want to stop reading this article right now and just stick with water based materials. For the rest of you that realize that every smell will not kill you, you may be rewarded with a nicer finish for having used an oil based material than if you were to head straight for the latex.
Where do oils outperform latexes and vice versa?
First oil based materials are petroleum based products and as a result these products will not hold up well on anything outside that is exposed to the sun. So with very few exceptions, oil based finishes should be considered more for interior projects rather than exterior.
Oil based material will often flow out nicer showing less bush strokes than a latex and can give a much nicer finish. Oil will also dry far harder than latex making it more resistant to wear and tear and will hold up infinitely better if what you are painting is going to be consistently handled. The disadvantages of an oil would be that they take a lot longer to dry, and will yellow anywhere where the product is exposed to less light (i.e. inside dark rooms, on the back sides of cabinet doors, etc.).
Walls should almost always be done with latex based materials, however in some older homes these walls may be better off repainted in oil, Once upon a time oil based materials were better at almost everything. They could run faster, jump higher and beat the crap out of anything that latex had to offer. Today that is not the case. So unless you have an older home where the interior walls were painted in oil, let’s keep all the walls painted with latex.
The trim of your home is a completely different story from the walls (trim includes doors, door trim, crown molding, base etc.). If the trim of your house is already painted in oil, you will be able to achieve a nicer finish over latex if you continue to use an oil based finish. If your trim is already painted in latex, there is no good reason to go and paint over that with an oil based material. So to summarize…
Water based latex finishes would be better if:
- you are painting something that is outside.
- you are extremely sensitive to smell.
- you are painting interior walls (be sure your walls are latex if you live in an old Victorian home for instance).
- The interior trim you are painting over was already done in latex.
- You would like an easier product to work with.
Oil based finishes would be better if:
- You are painting new interior trim, or the trim in your home was previously painted in oil.
- You are painting cabinets or something else that is handled regularly (there are better materials to paint cabinets with, but for the average do it yourselfer you probably will not be able to do anything fancier than this).
- You need a finish that is more durable than latex.
- brush strokes bother you and you would like a finish that will minimize the brush strokes, without having to spray it.
Beware painting over oil!!!
Probably the biggest and costliest mistake I see homeowners make (and some “painters” believe it or not) is painting over oil materials with latex. Although this can be done, if done incorrectly the finish that you put on will be able to be taken off with a scrape of your fingernail! Should you decide to paint a latex based material over an oil, be sure you are preparing your surface correctly or suffer the consequences!