Oil test
If you bought a piece of painted furniture at an antique store or live in an older home, it’s likely that the furniture or some of the woodwork, molding, cabinets or doors in your home were painted with oil-based paint.
Nowadays oil paints are rarely used and most paints you buy to paint your home are water-based latex formulas. But, now you know how to check to see if the paint is oil-based, before you start your painting project.
Time-Saving Primer Tip: Most primers are white. If you are painting a dark color over a previously light color of paint, buy or have the primer mixed to a gray color. This will help bring out the depth in the dark color and also save you time, since the dark base will lessen the need for multiple coats of paint to obtain complete coverage.
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I am wanting to paint radiators and wood work with a water based satin finish. However an oil based undercoat has been used to cover what was already there. I now realise I cannot use a water based paint on top of this. How can I easily and straightforwardly rectify this
without it costing me too much? Unfortunately the colour choice in oil based paint is very limited other wise it wouldnt be problem! Painting & Decorating
7
7 Answers from MyBuilder Painters & Decorators
Best Answer
You don't have a problem just give the rads and woodwork 2 or 3 coats of your water based finish.
Answered 16th Nov 2015
Lightly sand the surface to be painted so the waterbased paint has something a little better to adhere to then coat 2 coats on the top for a perfect finish. What you want to try to get to is sanding off the surface so it's not shiny
Answered 19th Nov 2015
When putting water based paint over oil based paints, you must sand and key the surface really, really well. Also use a good water based undercoat with good adhesion. Then go over the top with one or two coats of your desired water based top coat.
Failing to give a GOOD keyed and adhesion surface will result in the top coat failing/cracking/peeling etc.
Answered 23rd Nov 2015
you have to give the substrate your working with a good key so the water based paint you using will adhere to. You can use a water based Dulux ultra grip primer 2 part system which is designed to provide a key on difficult surfaces.
Answered 22nd Nov 2016
Hello,
It is a common mistake but I have a solution for you.
Lightly sand down the radiator and woodwork so the water based can stick a bit better.
You will have to give it 2 coats to act like a undercoat but once applied will look just as good as doing with undercoat and then finishing with gloss.
Regards
Buchanan Decorators
Answered 14th Jun 2017
This is not a major problem sand the woodwork down getting a good keyed surface then apply a coat of acrylic undercoat then once that's dry apply the satinwood
Answered 28th Jul 2017
This is not a major problem, sand the wood work and then apply an aycrlic premier before two of your top coats. I would not recommend a water base paint for radiators,it's always better to use an oil base for radiators. Also make sure the radiator is off before you paint it, otherwise it will turn white paint yellow'ish
Answered 29th Sep 2017
**If you have to paint over oil-based paints, it is important that the primer you use is also oil-based.
If it is not, the topcoat will peel or blister. Water-based paint can be used as a topcoat over water-based primer.
If you are using latex paint as a top coat, make sure that it is a low odor so that the fumes will not affect your health.
If you need to paint over latex paint, there are products available on the market with which this can be done.
However, these products cannot be used on oil-based paints and if you need to paint over oil-based paints, then they are probably not suitable for your need.
Is it possible to use water-based paint over oil-based primer?
The short answer is yes, you can use water-based products over oil-based primers.
The longer answer is that the underlying finish must be completely dry.
Water-based products, such as the Water Based High-Performance Topcoat, should be applied 72 hours after the oil-based products
How to paint over oil with Latex
As with anything else, preparation is the key to a successful finish.
Clean all dirt, grease, or other foreign substances from the surface thoroughly prior to sanding the walls with 220 grit sandpaper.
Before applying the new paint the surface should also be free of efflorescence (white salt deposits) and other signs of chemical leeching from the previous finish. Surfaces prepared in this manner will have a smooth finish and a uniform color when you are done.
Ensure that the old finish is completely dry before painting over it.
If you can lift any part of the old coat off with your fingernail, it is not yet dry enough to repaint.
The time required for it to dry naturally depends on factors such as temperature and humidity, but in many cases, it will take several weeks for oil-based paints and considerably longer for alkyd paints.
Can you paint oil paint over latex primer?
Oil-based paints or primers have a very strong solvent base, which will lift the existing primer or paint and cause it to wrinkle.
Once the oil-based paint begins to dry, there is no way to stop the reaction and you will be left with an ugly mess.
The use of oil-based paint over any surface currently coated with a latex product is strongly discouraged.
If you insist on using oil-based paint, you must wait at least 30 days after applying any latex product before applying the oil-based paint.
This 30 day “no contact period” will give the latex time to fully cure, eliminating any possibility that it could be lifted by the oil-based product.
Use an oil-based primer instead.
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Can you mix Oil with water-based paint?
Mixing oil and water-based paint can be tricky, but it is possible.
Oil and water do not mix well because they are immiscible.
Immiscible means that the two liquids are not able to blend or dissolve in one another.
The oil separates from the water and sits on top of the mixture.
If you want to mix the paints, you will need to use a binding agent, such as gum tragacanth or sodium alginate, which is derived from seaweed.
Quick Deep Dive
Gum tragacanth is an organic powder used as a thickening agent in many cosmetics, including toothpaste and shampoos.
It creates a gel when mixed with water and binds oils to the water.
Sodium alginate was first used commercially as a thickener for ice cream and has many medical applications.
It works similarly to gum tragacanth by stabilizing mixtures of oil and water, allowing them to remain blended together for extended periods of time without separating.
Oil paints contain pigment suspended in oil or wax mediums.
They are typically used for painting on canvas or wood panels; however, since their pigments are suspended in oil, they cannot be mixed with most water-based acrylic paints without separating within minutes of application onto the surface of your painting
Is oil primer better than latex?
Once upon a time, before latex paints became popular in the United States, oil-based paints were the only thing. Oil-based paints are still best for exterior projects (especially cedar), but latex paints are more convenient to use in interior situations.
Related Article: Best Oil Based Primers For Wood And More
- Oil and water don’t mix, so oil-based paints must be mixed with thinner before you can apply them. Latex paints can go on straight from the can. Latex paint cleans up with soap and water, while oil-based paint requires mineral spirits or turpentine to remove it.
- Oil-based primers are better than latex primers at sealing nail heads, covering knots in bare wood, and blocking tannin bleeding and other stains. They cover well over bare metal, and they’re widely used as a primer for topcoats of metal paint on steel objects such as cars and motorcycles.
- Latex primers work well on interior trim because they go on smoothly and cleanly. Oil-based primers require two coats for the same level of coverage, but latex primers aren’t recommended for use on exterior trim because they tend to peel off in hot weather.