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Highlander

Glass Smooth

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I need to create a glass smooth finish on a section of a figure -- even before final priming.  The casting has notable and numerous pits ... so there's gonna be some sanding.  To begin filling the pits, I chose  GW's Technical Ardcoat -- recommended by some -- applied as a coat straight out of the bottle.  The result, after about 18 hours of drying in a very dry climate, was a slightly sticky finish which sanded off, in times, as clumps and rolls.  But the pits seem to have filled in a bit.

 

I've decided I need another approach.  Tamiya putty, thinned, has worked for me in the past ... but thinning and applying it is messy an tedious and requires various chemicals.

 

Any other suggestions or corrections?

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How pitted?  I use one or more layers of Reaper brush on sealer to smooth figures. 

 

 

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You could try some self-levelling sandable automotive primer.

 

Just decant a bit from the spray can into a plastic cup or something, and flood it into the area that needs smoothing. You'll have to leave it to cure for at least 24 hours, I'd think, and depending on how bad the pitting is you might need a couple of applications, but with care and 2400 grit wet-&-dry paper it can give you a perfectly smooth surface.

 

Then, to get it mirror-smooth, flood-fill with a self-levelling acrylic like Future (or whatever it's calling itself these days).

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Thank you both.  Since  I have the Reaper sealer in hand, I'll try that first.

 

I also have Future, so I can follow with that.  Don't know if any auto shops are open.

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Methods I'm aware of for smoothing surfaces:

 

Just sanding and filing. For a very smooth finish you start with rougher tools and finish with higher value sandpapers. Feasibility affected by the shape of the surface. Relatively easy on a smooth flat surface, annoying on rounded cloak folds and the like, which are the very area most likely to end up pitted in my experience.

 

Some putties are water soluble after you mix them. Milliput is one, I think Apoxie Sculpt and MagiSculp probably have this property too. You mix a chunk, then put it in a little dish (like the plastic cube from a blister pack). Add a bit of water, and agitate the water against the putty with a brush. You will create a sort of putty 'slurry'. Paint this over your surface. Once it cures, you should be able to sand with higher value sandpapers to get a nice finish. Again, can be more or less of a pain depending on the shape of your surface.

 

Do as much surface prep as you can with the above methods and then apply sealer. For relatively minor issues, Reaper Brush-On Sealer works well though may require a few coats. For deeper pitting and scratches, you'll get farther faster with a gloss coat. 'Ardcoat or Reaper's Gloss sealer both work.  Future is going to be pretty similar here too. You need to apply this in as smooth a coat as possible. The issue with this is that you can end up _adding_ texture if you have a ridge around the edge where you add it, or brushstrokes if your sealer is super thick. (Thin it down a little with water if it's that thick.)

The sealer should be applied as the final step, I don't think it'd work well to sand it down. One thing to consider is that since all these products are transparent, you can't really SEE whether you've filled in all the texture. You may need to test by applying a thin coat of opaque paint or brush-on primer over the surface and then see what that looks like when it dries. If the surface still looks rough, do another coat or two of sealer, rinse and repeat.

Since these sealers are largely the acrylic binder portion of paint, it's fine to do this as a really last step. Prep as you can, use a good primer, and then check your surface. Add some coats of sealer as necessary, a coat of opaque paint to check the surface, and so on until you're happy with it. Note that this surface is to some degree a little more fragile while painting than you might think about. What I mean is, if you get a piece of lint or hair while you're painting, a lot of us scratch or scrape that out with a sharp tool or exacto blade or something, and that usually works fine. You've got just a few microns or whatever of surface built up from the miniature with primer and paint. If you're building up a smoother surface with a bunch of sealer, it's thick enough that it's noticeable if you scratch down to the figure surface, or you can dent it with a fingernail  while it's still curing. (Acrylic products take several days to fully cure.) It's generally not a big issue, just something to be aware of.

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2 hours ago, Corsair said:

Have you considered CA glue and baking soda? It should be sandable to smooth out.

 

I've used such on plastic models with mixed results.  The basic issue is that the resulting mixture fills well, but sets like stone and is devilishly hard to sand off without removing all the material round the pit.

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I use vallejo "plastic putty" alot. This is 100% acrylic resin and quite thin and sticky right out of the tube. Much like the tamiya stuff but without the need for chemicals, I just use water if I need to remove. 

 

Wipe it smooth with a finger or such and when dry it can be sanded.

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On 4/8/2020 at 1:24 AM, Maledrakh said:

I use vallejo "plastic putty" alot. This is 100% acrylic resin and quite thin and sticky right out of the tube. Much like the tamiya stuff but without the need for chemicals, I just use water if I need to remove. 

 

Wipe it smooth with a finger or such and when dry it can be sanded.

 

Does it sand?

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Unless Vallejo has changed the formula (I have a bottle not a tube), plastic putty is the same as liquid green stuff is the same as art store modelling paste. (Which cost per ounce is a LOT cheaper if you have friends you can go in with on a purchase.) I'm about 95% sure on that. It's flexible and probably pretty similar to the binder used for heavy body acrylic paints, if not pretty much just that exactly.

 

It's great for filling gaps as it's water soluble/smoothable. It's thick like frosting, so it seems to me like it would be a pain to work with to smooth a surface, but maybe I haven't played around with it enough.

 

I haven't tried sanding it. Next time I break some out I'll try to leave some globs set up on a piece of plastic to test sanding on. Since it's flexible and a lot like paint, my guess would be it's not going to sand down to a smooth finish like a hard putty will. A two part resin varnish that dries hard might, but that also sounds like a pain to deal with.

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I've tried Mr. Surfacer 1000 it has helped and it sands very well.  But the pits are not completely filled.  I'm reluctant to lay on a coat of acrylic paint -- gloss or otherwise -- after the unsatisfactory try with GW Ardcoat.  

 

More to come.

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12 hours ago, Highlander said:

I've tried Mr. Surfacer 1000 it has helped and it sands very well.  But the pits are not completely filled.  I'm reluctant to lay on a coat of acrylic paint -- gloss or otherwise -- after the unsatisfactory try with GW Ardcoat.  

 

More to come.

 

I think the issue you had with the gloss is related to sanding. You should be able to get a great smooth coat with gloss sealer, it's just not one you can sand down. Grab something like an old margarine tub or a piece of blister pack and do some tests. You could even scratch the plastic up with sandpaper or etch some gouges in and then test a few different options that you have to hand for smoothing it out. It's not exactly the same as metal pitting, but it's in the ballpark. Then paint a coat of paint over your tests and see which one ends up giving you the smoothest result.

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"Ah!", said he, a light dawning.

 

What I'm hearing is that one fills with putty's and green stuff and such.  And one should use the sandable versions.  However, one finishes a smooth job with a coat(s) of acrylic paint -- because it doesn't sand well  -- and which makes it smoother.

 

I'm doing tests for a clear acrylic gel in another application, but hadn't thought to do it with filling and smoothing.

 

Pardon the photos, but here's what I've been facing.  In the upper photo I have the front side of the board.  I tried to angle the photo so the light would catch the pits on the surface.  I have done nothing to this side but sand, sand, sand and polish, polish, polish.  It looks very good -- where there are not pits.

 

In the lower photo, I've attempted to fill pits on the back side of the board.  You can see the dark areas -- filled with Mr. Surfacer 1000 -- better, but not completely filled.  There are also some areas I have not attempted to fill.  You can probably see the difference.

 

Here's my plan going forward.  Have another attempt with Mr. Surfacer 1000.  Sand it down.  Then apply Mr. Surfacer 1200 -- which has the consistency of a thick acrylic paint.  If all appears smooth, lay on a coat of white spray primer and see if I've addressed my issues.

 

Sound reasonable?

 

 

IMG_3783.JPG

IMG_3781.JPG

Edited by Highlander

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1 hour ago, Highlander said:

"Ah!", said he, a light dawning.

 

What I'm hearing is that one fills with putty's and green stuff and such.  And one should use the sandable versions.  However, one finishes a smooth job with a coat(s) of acrylic paint -- because it doesn't sand well  -- and which makes it smoother.

 

I'm doing tests for a clear acrylic gel in another application, but hadn't thought to do it with filling and smoothing.

 

Pardon the photos, but here's what I've been facing.  In the upper photo I have the front side of the board.  I tried to angle the photo so the light would catch the pits on the surface.  I have done nothing to this side but sand, sand, sand and polish, polish, polish.  It looks very good -- where there are not pits.

 

In the lower photo, I've attempted to fill pits on the back side of the board.  You can see the dark areas -- filled with Mr. Surfacer 1000 -- better, but not completely filled.  There are also some areas I have not attempted to fill.  You can probably see the difference.

Here's my plan going forward.  Have another attempt with Mr. Surfacer 1000.  Sand it down.  Then apply Mr. Surfacer 1200 -- which has the consistency of a thick acrylic paint.  If all appears smooth, lay on a coat of white spray primer and see if I've addressed my issues.

 

Sound reasonable?

 

 

 

I think you're trying to skip steps. If you want a perfectly smooth finish skipping steps is just going to add to your work. First do more than one layer of 1000 before you sand. It shrinks while it dries so you need to account for that. Second if you still need to use 1200 you should sand it before priming. You need to put on enough to account for shrinking so if you're doing it right it won't be perfectly smooth. Third, if you can use a sandable primer. That way if you miss anything you can easy fix it with more sanding and filling instead of needing to try stripping the primer. If you want a truly glass finish you'd probably want to wet sand the primer layer, reprime, and wet sand again, but if you're painting with brushes once you've primed you can probably skip the wet sanding.

Edited by cmorse
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