Regarding Use Of Paint Primer: When To ?


  #1  
Old 01-25-07, 02:10 PM
R
Member
Thread Starter
Join Date: Apr 2005
Location: MA
Posts: 309
Likes: 0
Received 0 Likes on 0 Posts
Regarding Use Of Paint Primer: When To ?

Hello:

Not too sharp in the painting area.

Regarding Paint Primers:

Are there general rules of thumb for when, and where, paint primer should be used before applying the regular paint ?
Interested in both interior and exterior.

Would the answers be different for oil vs latex paints ?

Guess I should also ask if there are times when it should not be utilized ?

Thanks,
Bob
 
  #2  
Old 01-25-07, 02:47 PM
S
Member
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Likes: 0
Received 2 Likes on 2 Posts
Well there's lots of possible specific situations out there

But in general, there's not a need for primer when re-painting a surface that's been painted
In general, there is a need for primer on non-painted surfaces

If there's been a drywall repair, or the paint is scraped to bare wood, those would be considered non-painted surfaces, and would need primer

That would apply to latex or oil

A few exceptions to the rule would be certain specific coatings in certain areas/situations
Like Porch & Floor Enamel on a clean basement floor (no primer), or a drastic interior color change like brown to yellow (primer)
And depending on the condition of what's up there now, and what's going up, priming before re-painting a high humidity bathroom might be in order also
...or painting over oil paint with latex, that'll need an oil primer first


Usually the specifics and/or exceptions will be on the back of the can of paint you are applying
Or ask at your local paint shop
...or here
 
  #3  
Old 01-25-07, 02:50 PM
T
Member
Join Date: Aug 2000
Location: USA
Posts: 15,815
Likes: 0
Received 1 Like on 1 Post
There's a saying: "If in doubt, prime it!"
 
  #4  
Old 01-26-07, 03:29 AM
R
Member
Join Date: Dec 2006
Posts: 58
Likes: 0
Received 0 Likes on 0 Posts
Hello Bob,
Primers as a broad brush rule (groan - bad pun), are used when:
- The surface is bare - bare drywall, raw wood etc.
- The surface has possible adhesion problems - glossy or slick for instance.
- Stains that may bleed through - magic marker, grease, smoke as in fire damage, odor as in pet stains (cat urine in particular). etc.
- Changing from one type of coating to another - from an oil semi gloss or high gloss to a flat or semi gloss latex, clear polyurethane to a latex semi gloss, etc.
- As a shop coat to protect the substrate during shipment/storage.
- To seal in the edges or backside of wood to prevent moisture from being absorbed or transmuted - wood siding is often backprimed before being installed.
- When the substrate is one that is problematic for adhesion - glass, glazed tile, Formica, slick vinyl, vinyl coated wallcoverings.
- To provide a smooth even substrate for a top coat that provides even hold out of a finish with a sheen. Enamel undercoats for instance or auto primer.
- To protect metal from rust &/or oxidation.
- As a galvanic barrier. Zinc is the most well known substrate that reacts to most typical oil based finishes to form soaps. These soaps cause the finish to lose adhesion.

These are a few I can think of off the top of my head.

There's really no universal primer which works on everything, for everything. Pigmented shellac comes very close though for interior use. Even pigmented shellac has it's limitations though.

Best advice I can give is read the directions on the back of the can of the finish coat you're using & shop at a regular paint store instead of the big box places - thier help is generally more up on what to use where than the big box stores.

Here - this forum - is a good place to ask if there's any question about a specific project you're working on. In the brief time i've been here, I've found nothing but solid advice.
 
  #5  
Old 01-26-07, 02:01 PM
K
Member
Join Date: Aug 2004
Location: Vancouver, Canada
Posts: 1,210
Likes: 0
Received 0 Likes on 0 Posts
Usually a prime coat just serves as a *quick, inexpensive* 1st coat. Latex wall primer is essentially just cheap, watery, white paint. Some primers adhere better than regular paints, stop stains from bleeding, inhibit rust, etc. so you needn't include those formulations in the finish coats.
 
  #6  
Old 01-26-07, 05:01 PM
S
Member
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Likes: 0
Received 2 Likes on 2 Posts
Usually a prime coat just serves as a *quick, inexpensive* 1st coat
A very common misconception

Latex wall primer is essentially just cheap, watery, white paint
That is also a common misconception

Some primers adhere better than regular paints, stop stains from bleeding, inhibit rust, etc. so you needn't include those formulations in the finish coats.
That is somewhat accurate
Primers are meant to adhere, that's what they are for, and they do block and seal, and putting those properties into a paint would make the paint quality suffer
But perhaps we should address the misunderstanding Kobuchi and so many others have about primers

Primers are not paint
Primers are designed to seal surfaces, adhere strongly, and block stains
They are not meant as a top coat, and do not perform as such
They do not repel dirt, wash well, take color well, or last long if not top coated

Paint is not primer
Paints are designed to be a top coat
They look pretty, repel dirt, wash well, and can add durability to the surface
They do not seal well, adhere well, and block stains as well as primer/sealers

Which is why, at least on new unpainted surfaces, one needs to prime first, then paint

Making the paint act as it does, means it really doesn't make a good primer
Just as making the primer act as it does, means it will never be a good paint
 
  #7  
Old 01-26-07, 10:10 PM
K
Member
Join Date: Aug 2004
Location: Vancouver, Canada
Posts: 1,210
Likes: 0
Received 0 Likes on 0 Posts
Okay, liquid is not water.

Slickshift's definitions hit nearer to the mark. I agree.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: