Wood is naturally a porous material so it is important that the surface is sealed to ensure that solvents within subsequent coats are not absorbed too readily which will cause premature drying and potential failure of subsequent paint layers. A first coat of primer will also consolidate loose fibres on the wood’s surface which will enable sanding to a smooth finish before applying finishing coats.
There are a range of wood primers available, all with different qualities, and the choice can be confusing.
Water Based Wood Primers
Water based primers are often acrylic based, are more pleasant to use than solvent based alternatives and can perform well if used correctly. The advantages of water based primers are quick drying, good opacity (covering power), low VOC content and brushes can be cleaned with water.
Water based paints can not be used where the risk of rain is imminent and another disadvantage is that these kinds of paint can clog up abrasive paper which makes it difficult to get a really smooth finish. Some water-borne stains can also bleed through the surface of acrylic paints.
Quick Drying Primer/Undercoat is a general purpose acrylic wood primer and combined undercoat suitable for interior use in a range surfaces including softwoods, hardwoods and building boards including plywood.
MDF Primer is an acrylic primer formulated for use on MDF which is typically more porous than regular softwood. It is quick drying and can be used as an undercoat.
Rubol Primer Plus is a premium quality acrylic primer/undercoat for use on exterior timber. You can use regular water based primer outdoors but it’s worth spending a little extra to get the best result.
Oil Based Wood Primers
Solvent or alkyd based primers (commonly known as oil based primers) have been used traditionally to prime new wood. The advantages are that they dry to a hard finish that can be rubbed down to provide a smooth surface.
Oil based primers are compatible with traditional undercoat and gloss paint and will contribute to achieving a high sheen finish. The disadvantages are slow drying times and they can be messy and unpleasant to use.
Aluminium wood primer is an oil based primer with a high aluminium pigment content. Used for some hard woods which contain high amounts of resin which discolors traditional wood primer. Can also be used for very knotty timber where the use of patent knotting isn’t practical.
One problem with aluminium wood primer is that the bulk of the pigment will settle in the bottom of the can if left for even moderate periods of time so it’s essential that it is thoroughly stirred before use.
There are some other kinds of specialised wood primers but this covers the basics. The general rule with all types of primer is that thorough preparation will always yield good results and when selecting a primer for the job you should always use the best quality primer you can afford.
Kay
I have varnished knotty pine tongue & groove on my utility room walls & ceiling. I would prefer to use water based products & change the colour to Magnolia. If I were to firstly sand the knotty pine, would a water based primer & water based paint or emulsion be suitable to cover it. If not, what would you suggest?
Decorator
A water-based primer and finishing coats would probably work OK.
With the walls you may find that a water-based finish takes a long time to fully cure and can be easilly damaged with abrasion scuffs and scratches so be careful for a few weeks after painting in order to avoid these.
Chris
I have painted a new hardwood front door in Dulux aluminium wood primer. My wife has now found a F&B colour which she wants to paint this in but it is water-based. Will I achieve a nice finish if slightly sanding down the existing aluminium primer and applying a F&B primer/undercoat (also water based) followed by the top coat of F&B? Many thanks.
Decorator
Aluminium wood primer is not compatible with water-based paints. What you’ll need to do is apply a couple of coats of oil-based undercoat first and allow at least 2 weeks for this to fully cure. Then, and only then, you will be able to paint over this with your F&B primer/undercoat and finish.
Dominic
Hi there I’m getting a new front door made in sapele. The joiner is going to spray prime it using an unspecified water based primer. I’m not sure what is best to put over the top of that, I have also read that sapele really needs an aluminium primer to prevent bleed through/resin vapour making the top coat bubble? I want to make sure that the door is well protected against rot and swelling, and ideally want a heritage farrow and ball/little Greene gloss finish. But these paints dont seem to say much about how much protection they offer Vs Dulux weathershield etc? My door is east facing and relatively well sheltered with a small canopy porch thing above it. Thanks
Decorator
Since you say: your joiner is ‘going to spray prime it using an unspecified water based primer’ it doesn’t matter what you do. Best have a word with him before he causes you no end of further problems.
Barry
Help please. I’m about to paint 2 internal wood doors, sanded to bare wood. I’ve bought, both water based, Dulux Trader QD Undercoat and Dulux QD Satinwood ….. what Primer do I use? I can’t seem to find Dulux water based primer, only water based Undercoat & Primed combined. Thanks
Decorator
The primer/undercoat is fine, you can use that although you may need to thin the first coat down a little with water.
However, you need to be careful when priming doors with a water-based primer since it can lead to swelling of the wood initially. It is not certain since a lot depends on whether you are priming hardwood or softwood. Some softwood timbers are very susceptible. See the comment here: https://decorator.uk/contact/comment-page-1#comment-1076
If swelling is likely, I would use a regular oil-based primer (thinned slightly with white spirit). Allow to dry/harden for at least 3 days the run down to a smooth finish and THEN prime again with the water-based QD undercoat (no need to thin this time), then finish with 2 coats of QD satinwood.