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Do I need to prime first ??

8 replies
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  • Member since
    December 2014
Do I need to prime first ??
Posted by Goodwrench3 on Sunday, December 28, 2014 10:38 PM

I've built several NASCAR models over the past few years, each time using Testors enamel spray cans.  I've only used a primer on 1 of them (and only to affect the shade of the color coat).

I'm interested in trying the Tamiya lacquer spray on my next model (all white body color).  The model body shell is molded in white plastic.

My question -- do I need to use a primer first, and if so, why ?  I know I would if I was trying to cover a dark molded plastic color with white, but here the plastic is molded white.

Obviously, I'd like a nice smooth high gloss finish when done, so I want to do it right.

Many thanks in advance for the help.

  • Member since
    December 2003
  • From: Nova Scotia
Posted by Bainford on Monday, December 29, 2014 3:21 PM

It is not absolutely necessary to prime first in many cases, but there are several useful reasons for doing so. The paint you are using is compatible with the plastic, so that won't be an issue.

One of the biggest reasons for using primer on any kit is that it makes imperfections in the body easy to spot. The white plastic easily hides some mold lines, scratches and sink marks that a grey primer will make visible (and that paint will magnify). These can then be addressed before painting.

Since pretty much any body will require some degree of sanding/scraping to remove mold lines, primer makes areas that are not smooth enough after sanding easy to see and address. Primer also acts as a fine filler to help fill small sanding scratches.

If small sink marks are found and filled, primer will show if your repair is smooth and seemless afterwards, and will help in feathering the edge of the repair. The primer will also make the entire body all one colour before painting, covering areas of filler.

Most kit plastic has some degree of semi-transparency to it (even if it doesn't seem so). This semi-transparency greatly affects the colour quality and appearance of the finished product. A model painted without primer retains a plastic look, even after many coats of paint. Primer is opague, and makes the paint look solid and realistic.

Overall, primer makes all body work easier, and prepares the surface to accept paint. As you mentioned above, primer colour can be used to affect the final painted colour of the body. Grey primer is easy to work with when assessing if the body work is ready for paint, but can be recoated with white primer after the body work passes scrutiny, if a white base is desired.

There are other uses for primer as well, but these are the basics. Others will chime in with other reasons. Prior to joining this forum years ago, I never used primer. I figured that primer was used to promote paint adhesion, and I never had paint adhesion issues so why use it. Seeing the work done on this forum, I have learned the error of my ways. Primer is very useful and I can't imaging doing even the most basic build today without it. Primer is one of several basic processes that has resulted in a dramatic improvement in my body work, and resulted in dramatic improvements in the overall quality and appearance of my builds. If you are interested in upping your game and making better models, I highly recommend getting familiar with primer.

"It would be unusual, if the unusual didn't occur."

- Steamboat Gariepy


  • Member since
    December 2014
Posted by Goodwrench3 on Tuesday, January 6, 2015 7:55 PM

Thanks so much for the great reply.  I really appreciate your time.  It sounds like primer and I need to start spending some time together!  I see a lot of mentions of the Tamiya primer in the magazine and on the posts here, so that may be what I start with.

  • Member since
    August 2013
  • From: West Seneca, NY (Buffalo)
Posted by Snork56 on Tuesday, January 6, 2015 8:10 PM

Great educational reply, Bainford!  All newbies should be referred to your mini-clinic.  Maybe It can be put on BTD's (Ray) tutorial area!

To get back up when you are down, fight when you are struggling, give the extra effort when you are in pain, come back when no one expects you to and stand up tall when people try to pull you down.    That is what makes up a true champion!!   Snork56 (S56) Henry D.  

  • Member since
    January 2015
  • From: East Leroy, Michigan
Posted by bcthunderbolt on Monday, February 23, 2015 9:58 PM

Very detailed explanation bainford, I think you must have been in the auto industry in your previous life!

I like reading your reply's. Detailed and spot on.

Build um if you got um !

  • Member since
    January 2015
Posted by Kinshun Mui on Sunday, March 29, 2015 5:34 PM

Great reply.

Kinshun Mui

  • Member since
    January 2005
  • From: Cape Coral Florida
Posted by BigTallDad on Sunday, March 29, 2015 8:01 PM

Great reply! The only things I can add would be

  1. If starting on a fresh body, alternate the primer colors on the first few iterations of sanding; a dark/light combo will make any irregularities stand out and therefore easily addressed.
  2. Add this to the Tutorial collection, located at


"In order to teach a dog, you must first be smarter than the dog" P.R. Ferguson

  • Member since
    October 2018
Posted by RafaelShirk on Tuesday, October 16, 2018 1:26 AM

It is better to use dark colors to spray. I am a term paper writer and I suggest dark colors because which are easy to use. It you use white, you will be take extra care about it.

  • Member since
    August 2015
  • From: Hamptonville, NC
Posted by TarheelRick on Tuesday, October 16, 2018 3:30 AM

I am 70 years old, why would I need a term paper? SPAM!

I build models because I can't afford the real thing!


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