Painting Tips #3 - Primers

Over at Steve Dean’s excellent (but now defunct) Painting Forum there was a discussion about problems priming resin amongst other things.  Such threads are really rather common and it’s quite clear that there’s a lot of confusion about.

In this particular thread I was struck by one comment to the effect that there was no science involved.  The truth is just the opposite; there is a huge body of science behind surface coating.

Unfortunately, there are many formulation and application variables in play which can produce poor results.  Within the wargaming hobby this situation is compounded by unrealistic user expectations (such as a universal primer) and the tendency to use products for uses they weren't designed for (priming lead with car primer designed for ferrous metals for example).

For the befuddled, here are some priming basics you can rely on:

• Few primers will work on all surfaces or there is no universal primer.
  
• Resin, plastic, & metals have significantly different surface properties so will usually require different primers.
  
• Lead and tin have really different paint adhesion properties to ferrous metals so users of car primers beware.
  
• The primer is the first paint layer so poor priming will result in a weak overall paint job which no varnish can rectify.
  
• Primers have greater adhesion than standard paints. If you prime with paint, and it works, then count yourself lucky.
  
• A primer is different from an undercoat. Once a surface has been primed nearly any paint can act as an undercoat.

I won't even attempt to deal with the issues associated with spray vs. brush application but the above apply to either method.

I'm sure there are a lot of you now thinking "This isn't true because I use xyz and I've never had a problem." Not so. All it means is you've made a choice that happens to work and if I were you I'd keep my fingers crossed that the manufacturer never changes the product formulation (to improve its intended purpose or save money) and inadvertently ruins your hobby use.