When do I need to use an undercoat or primer when painting?

1829 Undercoat - grey and white available

People often confuse undercoats and primers, however they usually serve two quite different functions. Preparation before painting is extremely important and good preparation can maximise the final effect and also help to prolong the paint job before touch up is needed.

What is an Undercoat?

An undercoat is a base layer that is generally used to give a neutral base for you to paint your colour onto. The main reason for using an undercoat is to provide an even surface to paint on to, such as to cover a strong base colour or a patchy surface, so that it takes less coats to cover and does not affect the look of your chosen colour.

What is a Primer?

A primer is used to create a surface for the paint to adhere to, such as when painting onto wood or metal. Painting directly on to wood or varnished wood could mean the paint chips more easily, but using a primer can solve this. Specialist primers can also seal the surface to stop stains or discoloration from leaking through to your final layer.

What are the similarities between an undercoat and a primer?

Essentially both primers and undercoats help to prepare the surface before painting, in order to give your final topcoat a better finished look.

Which primer or undercoat should I use?

Once you have decided whether a primer or an undercoat is the correct product for your job, you should then ensure that you purchase one that is compatible with your chosen surface and topcoat. For instance if you are painting onto metal, choose a multi-purpose primer or metal primer and read the back of the tin to ensure it is compatible with the paint type and finish. Our Artisan range contains a metal primer, a plastic primer and an undercoat which are all spray paints. Our 1829 range contains an undercoat specially formulated for use under 1829 colours and Artisan brush on effects. (Please note glitter glaze should always be applied directly on to a Chalky Emulsion colour rather than directly on to an undercoat.)

Should I use a white or grey undercoat?

Our 1829 range of paints contains an undercoat that can be used on most interior and exterior surfaces (except for plastic and metal). It comes in both white and grey. The colourcard is clearly marked up to show which undercoat to use with each colour, as are the web pages for each 1829 colour.

What preparation do I need to do before using an undercoat or primer?

The most important thing is to read the manufacturers’ instructions on the back of the tin carefully. You should always ensure the surface is properly prepared before painting.  This will generally involve ensuring the surface is clean and dry, and as even as possible. Fill any holes or cracks with filler. If you are painting on to wood or a shiny surface, or an old coat of gloss or eggshell you should lightly sand the surface before painting so that the paint, primer or undercoat will stick more easily. This is sometimes called ‘providing a key’.

How long should I leave the undercoat to dry before painting over it?

The drying time and recoat time will be clearly stated on the packaging. We recommend leaving the 1829 multi-purpose undercoat for 4 hours before recoating or overcoating.

View our 1829 undercoats here, and our Artisan metal primer, plastic primer and undercoat here