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What's the purpose of glossing a surface if you're going to sand it?

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  • Member since
    May 2020
  • From: South Africa
What's the purpose of glossing a surface if you're going to sand it?
Posted by ohms on Saturday, May 23, 2020 12:29 PM

I don't wish to sound as inciteful as the heading suggests. But why add several layers of gloss only to sand/wet sand the surface afterwards? I've seen so many people on YouTube do this. 

Doesn't the sanding go through the gloss, or at least ruin it? 

If not (let's say you gently wet sand a 3x layer gloss surface), what's the purpose? Is it to flatten the surface and help give it that mirror finish? 

There's a guy on YouTube who said that he airbrushes a little bit of thinner over his gloss coats shortly after applying them to sort of 'melt it down' and even it out. If I did this, would I still need to sand over it? 

I just don't understand the purpose of the sanding over gloss. I know people then use the polishing compounds, but why not just use the compounds directly over the gloss without the sanding? Please help me understand this.

 

  • Member since
    May 2013
  • From: From the Mit, but live in Mason, O high ho
Posted by hogfanfs on Saturday, May 23, 2020 12:52 PM

ohms

 Is it to flatten the surface and help give it that mirror finish? 

Yes. 

At least when I was painting my motorcycle race skins. (And I am no professional painter) I would do this same procedure. Glossing then lightly sanding the surface would take out most imperfections. If I would have taped and painted with multiple colors. I would sand to take down the edges. Granted with progressively softer grit paper. I have a few autos and motorcycles in the model building queue, that l will take the same approach. 

 

I hope this helps,

 Bruce

 

 On the bench:  1/48 Eduard MiG-21MF

                        1/35 Takom Merkava Mk.I

 

  • Member since
    October 2019
  • From: New Braunfels, Texas
Posted by Tanker-Builder on Sunday, May 24, 2020 8:19 AM

Hi OHMS;

      We automotive types and model types do this to take out last minute imperfections before buffing and bringing out that beautiful gloss everyone seems to love, I used to do a misting of two parts thinner, one part retarder and one part paint. This created a glaze that didn't require buffing. BUT, the surface had to be sanded lightly to get it to stick good.

  • Member since
    November 2009
  • From: Twin Cities of Minnesota
Posted by Don Stauffer on Sunday, May 24, 2020 8:40 AM

Personally, if the gloss coat is dust- and imperction-free I do not sand it. I have found decals stick fine to gloss overcoats.

If I am doing a high-gloss custom car then I may polish it to get a better gloss, with wax after polishing.  However, for most gloss finishes the only reason to sand, with say 2000 or 4000 is to get rid of dust specs and other tiny imperfections.

 

Don Stauffer in Minnesota

  • Member since
    April 2020
Posted by Eaglecash867 on Sunday, May 24, 2020 9:58 AM

ohms

There's a guy on YouTube who said that he airbrushes a little bit of thinner over his gloss coats shortly after applying them to sort of 'melt it down' and even it out. If I did this, would I still need to sand over it? 

I recently used this kind of technique for the gloss white interior of a 1/32 F-16C intake tunnel.  In that scenario, due to how the air flows through a tube, even the gloss paint ended up with a flat, textured look.  Then I sprayed some more of the gloss white, but with mostly thinner, and ended up with a smooth, shiny interior of an intake that built up from 4 pieces and ended up with no visible seams.  I followed up with a good polishing, using Novus and cotton gloves.

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

  • Member since
    May 2020
  • From: South Africa
Posted by ohms on Sunday, May 24, 2020 1:24 PM

Thanks everyone, I really appreciate the replies. 

I suppose I'm going to have to go through good ol' trial and error. There are some things said above which I'm not sure I understand 100%. Got about 7 flat pieces of plastic which I'm going to use as a canvas and experiment on tomorrow.

None of my questions would be necessary if the model makers on YouTube made uncut, 15-hour long videos. Stick out tongue

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