Paint vs primer

I suppose this has come up before but I only now wanted to know this.

What is or are the basic differences between latex primers and latex paints? I understand their different intentions and uses but what makes a primer a primer and what makes paint paint?

And while we are at it what is the difference in sheens? What makes flat flat and what makes glossy glossy and everything in between?

 

Primers are formulated differently than paint. Wear and fading are a priority with finish paint but not with primer. It's a little hard to give one definition for primer as there are different primers for different needs but basically primers are formulated for adhesion and sealing. The adhesion and sealing properties will be different depending on what use the primer was formulated for. If you want a more technical answer we might need to find a chemist

The basic sheens are flat, satin/eggshell, semi-gloss and gloss. The problem is there isn't an industry standard for sheens so 1 manufacture's [or even line of paint] might have more or less sheen than the competitors. I've been told what the main ingredient is that controls the sheen but I've long since forgotten what it was Basically any paint as long as it's the same type [oil, latex,etc] can be intermixed no matter what the sheen level is although mixing equal amounts of flat latex with gloss latex won't necessarily give you a semi-gloss - more than likely the result will be a somewhat flatter sheen. While that's an over simplification of what paint manufactures do, they do it with precision so they always get the same sheen. Intermixing paints in the field will work but it would be next to impossible to duplicate later.

Any special reason for your interest?

 

The reason I am asking is because I have some paint I would like to use for a temporary wall to keep out dust from the rest of the place but it has to look good for a couple months. I have paint but wonder if I need to spring for some primer first. The wall is fire taped only and a uniform color will be acceptable. If I mix all I have together in a 5 gal bucket I will likely get a beige or light taupe. Main thing is uniformity.

 

If you thin the paint about 10% or so, you can use it for a primer. A separate primer is better but it is possible to use coatings for jobs other than their intended uses. If the wall is clean of all drywall dust, the thinned finish paint will adhere ok, it might not do a good job of holding a consistent sheen with the top coat but that shouldn't be an issue if your using flat paint.

Just reread where you say 'temporary wall' Does that mean the wall will get torn down later? If so, I'd just sweep off the dust and apply a liberal coat of unthinned paint [assuming the paint is flat latex, enamels would need a primer] Most painters and those who are extra picky will be able to tell it isn't quite right, but it should be good enough for a temporary wall.