Sanding after priming

[blunce]

I prefer to prime all my models before paint, but I'm getting tired of having to sand down a grainy primer. Is it not possible to get the prime coats to go down smooth ?

Here's what I've done in the past:

Normally: I've been using Mr. Surfacer 1200 (jar) thinned 1:1 with Lacquer thinner and probably about 20psi. The result is a rough texture something like 400g sandpaper, maybe a bit finer.

Just tried: Hoping for better results and trying to avoid possible paint/thinner ratio errors, I thought I'd try some Tamiya surface primer (gray), but decided to decant it as I have a hard time shooting rattlecans at anything I'm building. So the can I decanted had been sitting around forever, and the way I decanted it was to just grab it, no shaking, puncture the top and let it gas out. When I did that, there was of course some clear liquid expelled. After about an hour or two I opened up the can and was surprised at how little primer was in there compared to the size of the can . I poured out all the primer into a storage jar (old, clean Alclad jar), and poured a bit of lacquer thinner into the can to try and get as much of the primer from the can as possible. So there was some lacquer thinner added to the mix, but very little. I thought I'd heard that you can just decant Tamiya SP and use it straight without any thinning-- is this true?

Anyways, long story longer , I sprayed it today and while it did go down much smoother than previous Mr. Surfacer adventures, but it's still a bit rough, and I've had to use the nail polishing squares (side 1&2) to smooth it out. It's a real PITA and I'd really like to know what I'm doing wrong to get the rough prime coats. I don't have this problem with my paints so I'm confused. Only thing I can think of is not thin enough primer, but then too much lacquer thinner would just make the primer dry before hitting the model wouldn't it?

So any and all tips on the stuff I've been using/doing or what are you using?

[toadwbg]

Tamiyas primer out of a can has given me near perfect results. Smith as a baby's bottom right out of the can with no drips or runs. I never had a reason to decant.

[PNW_Modeler]

Tamiyas primer out of a can has given me near perfect results. Smith as a baby's bottom right out of the can with no drips or runs. I never had a reason to decant.

But good luck finding a can anywhere.

[tempestwulf]

Oh my my my. Dear friend, 1:1 with Mr Surfacer is far from enough. At least 3/1 at a minimum for Mr Surfacer as it's basically a thinned putty not a pigment. Same if using Mr Color lacquers. Those you can get away with 2/1 minimum. Drop the spray down to 12-15psi max too, the airbrush should be about 1-1.5 inches away from the model when spraying too and don't try to puddle it too. Lots of light coats are the norm.

How do I know? Experience. I first used Mr Surfacer on a 1/72 F-86E using your method and found it left something resembling 400 grade sandpaper. It's about mixture and pressure, be patient as it'll take a good few coats to get right but will be substantially smoother. Also try buying some spongy nail pads, they work great for sanding it would without gouging the primer.

[blunce]

Oh my my my. Dear friend, 1:1 with Mr Surfacer is far from enough. At least 3/1 at a minimum for Mr Surfacer as it's basically a thinned putty not a pigment. Same if using Mr Color lacquers. T

Well, that must be the problem. I know I've had it thinned (or lack there-of) to the point where I was getting spiderwebs. I think when I googled thinning ratios for Mr. Surfacer, I thought the consensus was 1:1.

I'll give 3:1 or more a try and see how that goes. I know thats what Honza is using as I asked him about his prime coats on the Hornet he just did and just the primer alone looked amazing! I wonder if I ought to throw some more thinner into the Tamiya Surface primer I still have to get a smoother coat???

[Netz]

It's just not thin enough, I don't think the pressure is too high, I routinely run 20psi, but you need to get a thinner mix, also if your thinning with lacquer thinner, add about 20% paint thinner in with it, it will act as a retarder.

Don't be afraid of using the Tamiya Spray cans, the paint is very fine and goes on nice, it's not like your using Krylon.

I'm the same as you and would never contemplate spray canning a model, but I was given some Tamiya spray lacquers and did a base coat on my F-16, and am throughly impressed with the finish, now I have no fear in finishing my Calsonic Skyline (TS-44)

Curt

[randypandy831]

try using more thinner and spraying closer. it's most likely drying before it hits the surface causing the grainy feel.

[blunce]

try using more thinner and spraying closer. it's most likely drying before it hits the surface causing the grainy feel.

I'm know my distance is good. I'm sure now that I'm just not running enough thinner.

@Netz- Are you talking about adding regular paint thinner/mineral spirits as the retarder?

[Mike C]

I always use Tamiya primer straight out of the can. Lays down nicely. Try giving it a real good shake, 'till your arm feels like falling off! Will also help to warm the can first: put it in your pocket for 5 minutes or more before spraying. Or immerse in lukewarm water.

Also, which Tamiya primer do you use? I think there are two different "grades": "standard" and "fine". I usually use "fine".

[toniosky]

But good luck finding a can anywhere.

No pb, buy it on an European online store

[Netz]

I'm know my distance is good. I'm sure now that I'm just not running enough thinner.

@Netz- Are you talking about adding regular paint thinner/mineral spirits as the retarder?

Yes, I like to thin with Lacquer thinner as it cuts the paint better, but as we all know it also will dry the paint faster, so adding a but of regular paint thinner will help keep the mix "wetter" when it comes out of the brush.

Curt

[Janissary]

I have had the same problem in the past with Surfacer 1200 + regular lacquer thinner. I have found Mr. Hobby leveling thinner (not the regular version) to be the answer to my problem.

[balls47]

I have used 0000 steel wool to work down primer that sandpaper or sanding sticks won't get to (wing to fuselage joint, etc.). You'll just have to clean it up well.

[Uncle Uncool]

I have had the same problem in the past with Surfacer 1200 + regular lacquer thinner. I have found Mr. Hobby leveling thinner (not the regular version) to be the answer to my problem.

:blink: Noooiiiceee...!!! Mr Hobby levellin' thinner ya say? Or is it Mr Colour levellin' thinner? Mind uplodin' some info regardin' it or at least a picture od "them" bottle, please, Jay-mate? Whut ratio do ya use with it 'n' Mr Surfacer 1200?

I have used 0000 steel wool to work down primer that sandpaper or sanding sticks won't get to (wing to fuselage joint, etc.). You'll just have to clean it up well.

0000 steel wool? D'ya happen to know whut company commercialises it, lad?

Cheers now,

Unc²

Edith Piaf: Also, whut do ya get rid of the dust with after ya scrub "them" primer with the steel wool?

Edited May 28, 2011 by Uncle Uncool

[toadwbg]

: put it in your pocket for 5 minutes or more before spraying.

Is that a can of Primer i'n your pocket or are you happy to see a 1/32 Tamiya Mustang?

[Mike C]

Is that a can of Primer i'n your pocket or are you happy to see a 1/32 Tamiya Mustang?

:rofl: :rofl:

[RAIN]

Can you sand down the Tamiya light gray fine primer?

[blunce]

Can you sand down the Tamiya light gray fine primer?

Yes, its possible, but a pain especially in detail areas. The goal is to not have to sand your prime coats.

[RAIN]

Yes, its possible, but a pain especially in detail areas. The goal is to not have to sand your prime coats.

But isn't primer supposed to be done to shoe possible blemishes?

[TXCajun]

Oh my my my. Dear friend, 1:1 with Mr Surfacer is far from enough. At least 3/1 at a minimum for Mr Surfacer as it's basically a thinned putty not a pigment. Same if using Mr Color lacquers. Those you can get away with 2/1 minimum. Drop the spray down to 12-15psi max too, the airbrush should be about 1-1.5 inches away from the model when spraying too and don't try to puddle it too. Lots of light coats are the norm.

How do I know? Experience. I first used Mr Surfacer on a 1/72 F-86E using your method and found it left something resembling 400 grade sandpaper. It's about mixture and pressure, be patient as it'll take a good few coats to get right but will be substantially smoother. Also try buying some spongy nail pads, they work great for sanding it would without gouging the primer.

Wulf is right, but I go a step further. I thin it down so I can spray at 10-12 psi and I never shoot that close to the model. 4-5 inches is the closest I go unless I am shooting very narrow lines for camo demarcation.

[blunce]

But isn't primer supposed to be done to shoe possible blemishes?

That is one reason to prime. I do it a different way by applying the same type of panel line wash most do after paint, on the bare plastic. The color seeps into all errant scratches, holes and so on. So by the time I'm ready for primer, I'm still priming to make sure everything is ok, but the last thing I want to do is spend hours smoothing out the primer I just laid down, working around delicate details and such. To me, by the time you're pulling the trigger on primer, you ought to be 95% ready for paint. Just a few spot fixes here and there, no need for a full sand all over again. That's the goal anyways, as you can tell from this post, I've not been having success at that lately! Somewhere along the line I forgot how much to thin it I guess, because I never used to have this problem.

I'll be using the tips mentioned here to refine my technique.

Thanks all!

[PetarB]

Can you sand down the Tamiya light gray fine primer?

There should never be a need to do this. Tamiya light gray fine primer is what it says - fine. I only model 1/72 and I've yet to see it fill any detail, ever. Never had a need to sand it.

[blunce]

Oh my my my. Dear friend, 1:1 with Mr Surfacer is far from enough. At least 3/1 at a minimum for Mr Surfacer as it's basically a thinned putty not a pigment. Same if using Mr Color lacquers. Those you can get away with 2/1 minimum. Drop the spray down to 12-15psi max too, the airbrush should be about 1-1.5 inches away from the model when spraying too and don't try to puddle it too. Lots of light coats are the norm.

HOLY CRAP, what a difference! I used your method. 3:1 lacquer thinner to Mr. Surfacer 1200, and about 10% Mona Lisa thinner (mineral spirits) and it went on like a dream. I did underestimate how much I would actually need though, not taking into account how much thinner it is. NO MORE SANDING! Thanks guys! I guess somewhere along the lines I forgot how much to thin that stuff, either that or just assumed that if I wasn't getting spider webs, then it was thin enough.