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Sanding after priming

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  • Member since
    March 2021
Sanding after priming
Posted by bapowellphys on Tuesday, September 20, 2022 1:23 PM

Hi all,

I'm interested in polling the group on this question: How many of you sand after priming?  I know some modelers do it, but I do not and I honestly don't see a strong reason, as the primed surface is generally quite smooth.   Is it smooth enough?  Dunno...I guess a metallic finish but be an exceptional case, but for my 1/72-scale military aircraft that I typically build, I don't see an obvious need.  Am I missing something?

Thanks gang.

Brian

On the Bench: Realspace Gemin-Titan

On Deck: Fujimi 1/72 F-4 Phantom

Check out my latest builds here!

  • Member since
    January 2020
  • From: Maryland
Posted by wpwar11 on Tuesday, September 20, 2022 2:20 PM

This is a great question as I often wondered the same thing.  I'm thinking if there is dust or imperfections in the primer coat sanding would be a necessary step.  

  • Member since
    April 2020
Posted by Eaglecash867 on Tuesday, September 20, 2022 2:53 PM

wpwar11

This is a great question as I often wondered the same thing.  I'm thinking if there is dust or imperfections in the primer coat sanding would be a necessary step.  

 

Yup.  That's the only time I would sand after priming.  If some errant piece of schmutz ends up getting on something while I'm priming.  Otherwise, I think sanding primer kinda defeats the purpose of a primer, which is supposed to give something for subsequent paint layers to hold onto.

"You can have my illegal fireworks when you pry them from my cold, dead fingers...which are...over there somewhere."

  • Member since
    March 2003
  • From: Towson MD
Posted by gregbale on Tuesday, September 20, 2022 4:29 PM

Likewise will sand for imperfections, but here's a tip - giving it a good rubdown with a section of fine mesh like panty hose/ stocking material will sometimes polish out rough spots with less angst (and damage) than sanding...again, sometimes making re-priming unnecessary.

It's worth a try, especially for small flaws or bits of lint. (Also good for just buffing any painted suface to knock the grain down.) Big Smile

Greg

George Lewis:

"Every time you correct me on my grammar I love you a little fewer."
 
  • Member since
    April 2020
Posted by Eaglecash867 on Tuesday, September 20, 2022 4:49 PM

Oh...forgot to mention that when I'm sanding the imperfections, I'm usually using a 3200 micromesh stick, to avoid the possible damage and re-priming that Greg mentioned.  Its just aggressive enough to remove the schmutz without removing much of anything else.

"You can have my illegal fireworks when you pry them from my cold, dead fingers...which are...over there somewhere."

  • Member since
    November 2018
Posted by oldermodelguy on Tuesday, September 20, 2022 5:37 PM

Generally speaking No but I have. As others say, where sanding is needed. That piece of dirt that fell into the last coat in of course the most obvious place. Or maybe something was a bit out of range and the primer laid down fuzzy there. But overall no sanding, I have both Stynylrez and Mr Primer Surfacer going on nice and smooth for the most part.The only two primers I use are those anymore. Depending where the spot is or the fuzz I'll use OOO steel wool or 1500-2200 micro mesh pad. 000 or 0000 steel wool is capable of polishing primer though which defeats the primers purpose IMO. So I tread lightly, just get the grit out. The pads are a better choice in reality if careful. I suppose I could go to 2500-3000.

  • Member since
    July 2014
  • From: Franklin Wi
Posted by Bakster on Tuesday, September 20, 2022 5:50 PM

For me it depends on how good it goes down and seldom does it go down perfectly. Usually, I give it a light sanding to knock the peaks down. I like an overall smooth finish on my models and paint grain is cumulative. 

  • Member since
    October 2019
  • From: New Braunfels, Texas
Posted by Tanker-Builder on Tuesday, September 20, 2022 6:52 PM

Hi Brian:

      Well, it doesn't really matter, but when I do, I use a "Brillo" Pad, Yes, Guys and Ladies, A "Brillo" pad with warm water. The soap acts as a lubricant and the metal mesh cuts the "Smutz" off evenly. NOTE:

 You MUST NOT scrub heavily though. Or you'll have to prime again. Don't forget to use a childs toothbrush and clean away any soap that gets caught in tight spaces or spaces that a part has to locate in!

  • Member since
    March 2022
  • From: Twin cities, MN
Posted by missileman2000 on Wednesday, September 21, 2022 3:32 PM

I always sand primer if it will be under gloss finish.  If I get a perfect primer coat and it will be under a matt finish I may elect to skip sanding (but I don't frequently get a perfect coat).

  • Member since
    September 2006
  • From: Bethlehem PA
Posted by the Baron on Thursday, September 22, 2022 9:48 AM

It can depend on the primer, too.  I use Tamiya's Fine Surface Primer for most jobs now, and it produces a nice, smooth surface.  I used to use Rustoleum's primer, and Walmart's house brand automotive primer, till I ran into problems with the cans clogging.  Those primers produced a surface that was a little rougher, and for some projects, the primer did benefit from a little bit of sanding.  Though it was often sufficient to use a green kitchen scouring pad, or even a piece of coffee filter paper.

The bigger the government, the smaller the citizen.

 

 

  • Member since
    March 2022
  • From: Twin cities, MN
Posted by missileman2000 on Saturday, September 24, 2022 8:17 AM

the Baron

It can depend on the primer, too.  I use Tamiya's Fine Surface Primer for most jobs now, and it produces a nice, smooth surface.  I used to use Rustoleum's primer, and Walmart's house brand automotive primer, till I ran into problems with the cans clogging.  Those primers produced a surface that was a little rougher, and for some projects, the primer did benefit from a little bit of sanding.  Though it was often sufficient to use a green kitchen scouring pad, or even a piece of coffee filter paper.

 

Yes, I do use the Tamiya fine primer when I want a super finish.  However, it is more expensive than the primers I often use, and not as easy to find around here.  I ordinarily use auto body primer.  I had been using Rustoleum sandable primer, but they seem to have changed formula recently and I won't use it any more.

 

 

  • Member since
    September 2006
  • From: Bethlehem PA
Posted by the Baron on Monday, September 26, 2022 1:39 PM

missileman2000
 
the Baron

It can depend on the primer, too.  I use Tamiya's Fine Surface Primer for most jobs now, and it produces a nice, smooth surface.  I used to use Rustoleum's primer, and Walmart's house brand automotive primer, till I ran into problems with the cans clogging.  Those primers produced a surface that was a little rougher, and for some projects, the primer did benefit from a little bit of sanding.  Though it was often sufficient to use a green kitchen scouring pad, or even a piece of coffee filter paper. 

Yes, I do use the Tamiya fine primer when I want a super finish.  However, it is more expensive than the primers I often use, and not as easy to find around here.  I ordinarily use auto body primer.  I had been using Rustoleum sandable primer, but they seem to have changed formula recently and I won't use it any more. 

Yeah, I used Rustoleum and the Walmart primer, too, because it was cheaper by volume.  Then I tried the Tamiya primer, and I found that though the cans are of a smaller volume, the contents went farther and covered better than the larger cans of automotive primer.  I also found that both Rustoleum and Walmart changed something with the design of their rattle cans, that they clogged consistently with about half the contents left in the can.  Not the nozzles, but the neck of the can where the nozzle inserts.  Rustoleum changed its caps, too, and they clogged after a few minutes of spraying.  I found online that some people wound up drilling out the aperture to deal with it.  But that's too much fuss.

That was another reason I stopped using those brands.

The bigger the government, the smaller the citizen.

 

 

  • Member since
    April 2020
Posted by Eaglecash867 on Monday, September 26, 2022 1:51 PM

If you decant and airbrush your Tamiya primer, it goes even further.  I decanted the entire contents of a can of Tamiya primer into a 4 ounce mason jar probably 3 or 4 months ago, and I still have plenty of it left...I prime everything with it, and prime something at least 3 or 4 times a week.

"You can have my illegal fireworks when you pry them from my cold, dead fingers...which are...over there somewhere."

  • Member since
    November 2018
Posted by oldermodelguy on Monday, September 26, 2022 5:21 PM

If I'm going to use lacquer primer this is all I stock and in bottle not rattle can, this is copy and pasted from the Mr Hobby web site:

MR. PRIMER SURFACER 1000

Detail

This is a surfacer with primer (base filling paint).
The material used in Surfacer 1000, which is gaining overwhelming popularity for plastic models has been improved for this product.
Surface attachment has been enhanced not only for plastic models but also for metal in etched parts and resin.
Spray type and bottle type are available. Color is gray.

 

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