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Materials Monday: Making a Mirai Cortex doll with blended seams

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Last week's topic was assembling the skeleton, which only applies if you got the Final Boss grade cortex kit.  This week's tutorial is about hiding seams will apply to both Ninja grade or Final Boss grade.  You can kindof sortof get it to work on a pre-assembled doll, but the most effective method of seam blending (using plastic model cement glue to fuse parts together) won't work if you've already had your doll glued together.

Wait, what about the assembling it bit? 

Watch Danny's video.  Yes, it's long.  Yes, you should still watch it.  I watched it when it first came out, before the dolls were even available to buy.  I had it on in the background while I sewed.  I got my cortex kit about a month later, and popped the shell together over the skeleton for a dry run (as in, no glue) in about 15 minutes.  It was very easy, because I had watched the instructions.

And yes, you should DO A DRY RUN.  Some of the bits can be a little tricky to fit together, and you obviously want to not be fiddling around trying to get them to match up while there's glue all over the place. Put pieces together, take them apart, put them together again.  Can do it smoothly without having any bits catch or not want to go together?  Then it's time for glue.


Like I said: this week's blog post is about assembling the shell with the goal of hiding the seams.  I was pretty sure I knew how to hide the seams like someone had in the 'seam hidden' demo doll Danny showed in his video.  I thought it would be a matter of using plastic cement to fuse the seams together, then just sanding them down and maybe applying a little filler and touching up hairline cracks. 

That's pretty much exactly how it went when I used the bust to test this method (because I bought a soft bust since the hard bust limits posing).

The seams were still visible, but they were only as visible as the mold seams on the doll itself.  Fantastic! 

Unfortunately, the rest of the doll didn't work out quite as perfectly. But I'll get to that later.

Here's the stuff I used:

  • Testors Plastic Model cement.  As I mentioned, this stuff works differently from super glue.  Instead of creating a clear bond between two pieces of plastic, it uses an acetone based formula to slightly melt and fuse two pieces of plastic together.  I know, some of you read "acetone based formula to slightly melt and fuse two pieces of plastic" and suddenly needed a fainting couch.  Yes, yes.  Get over it, this is a model kit.  Plastic cement has been formulated for model kits and used on model kits for a long time, it works well.  It also avoids the problem of old super glue yellowing and cracking.
  • Mr Base White 1000.  This is a modeling product that is supposed to level small defects while priming.  I also used Mr Surfacer 500 but if I did it again, I wouldn't, I'd just use multiple layers of Mr Base white to fill the bigger cracks. 
  • Razor Blade For scraping/smoothing anything that can be taken off more easily with a razor than with sandpaper.
  • Lots of sandpaper, in 400 to sand down the filler, and 800 to smooth everything out.  Wet/Dry sandpaper works best because wet sanding works faster/easier, BUT make sure you don't want to get water on the inside of your shell.  There are metal screws in there, and I'm not sure if they're rust proof.
  • Paint I use Golden Fluid Acrylics, but any acrylic designed for plastics should be fine too
  • Pastels (matched to the milk skin).  I used this to blend the painted bits with the non-painted bits.
  • Mr. Super Clear (or some other matte sealant).  This did a good job giving painted and non-painted bits a uniform surface look.  It also seems to be doing a great job of making the plastic shell less scuff-prone so I don't have to buff it out every 5 minutes.

The main problem was that Model cement worked great on 2-part molds that pressed together in a straight line (the bust, the torso) but NOT on parts that had a panel (upper and lower legs, upper arms). 

These seams didn't work well with the cement because the panel slides into the main part.  If you press one side tight enough to get a fuse that results in almost no visible seam, the other side is going to have a corresponding wider gap. It took me a little to figure out that was what was going on (vs me not pressing the right way or hard enough) and naturally, most of my best fused seams are on the inside.  Sigh.

TIP: When you use Plastic Cement, DO NOT WIPE SEAMS.  If you get little beads of cement squeezing out between your seams, it's fine, don't touch them.  It's plastic-melter.  Only put it on things you want melted.  Wait until it dries, then scrape it off with a razor blade.

After the plastic cement was applied I filled the big gaps with Mr Surfacer.  Remember, if I did this again I'd just use multiple coats of Mr Base White, which has a finer filler.  That's because color matching over white is easy, color matching over white and dark gray mottled together, not so much.

So just pretend this picture is layer 1 of Mr Base White.

After this dried, I sanded everything down smooth, and applied Mr Base White to everywhere the Plastic Cement hadn't fused a perfect seam and on top of the gray filler, and then sanded everything again.

Unsanded on the left, sanded on the right.  So much sanding.  So much.  By the way, I spread these steps over a week and it was still brutal on my hands.  I do not recommend doing this all at once. 

Next was the painting and... honestly?  I became pretty disheartened at this point.

Let me explain: The bust had come together perfectly.  I had barely needed to paint, and what paint I did apply was put on hairline cracks, which are pretty easy to match/blend.  The body, totally different.  Instead of hairline cracks, I have gaps up to 2mm wide with irregular edges.

I COULD have airbrushed the seams, which would have made them virtually invisible to the camera, but that's really not what I wanted to do.   Airbrushing is very fragile, even under layers of sealant, but the bigger issue is this:

Plastic is semi-translucent, just like real skin.  Paint is not (or at least it's not when it's thick enough to wholly recolor something vs tinting).  Paint reflects light differently too, so what might appear to be a perfect match in, say, white light, is obviously not a match in warm, yellow, incandescent light. The bigger the area you paint, the more obvious it becomes.  Hairline cracks, you can get away with.  2mm gaps, no. 

I've customized hundreds of dolls and done some really crazy things with paint.  I can tell you that when it comes to painting the skin to match the the plastic, if you want a perfect match in all light, it's all or nothing. 

Paint is a last resort.  It will make the skin flat and less luminous and super, super easy to damage.  The whole body becomes one big cheek blush waiting for a rub.  Painting Cortex, which already scuffs just from handling, is something I did NOT want to do.


So here's what I did do: I used translucent paint and pastels to make the fillers less obvious without having to coat the whole doll.  It's not perfect, it kind of looks like what happens if you have someone covering up a scar or tattoo with makeup.  Better than no makeup, but not better than no scar/tattoo.

First I painted, applying paint over the seams with a brush to bring the white up to match the skin.  Second, I blended the opaque seam to the translucent plastic on each side with a sponge.  Third, I applied a coat of MSC to the whole body so that the surface of the doll would be uniformly matte.  Fourth, I added flesh-toned pastels over places that were still obviously painted, Fifth I applied more MSC.


What I'd do second time around:

  • When dealing with panels, I'd make sure that the fused seam is on the outside of the body.
  • No Mr Surfacer.  Just Mr. Base White, and I would tint Mr Base white to match the color of the doll body before I applied it.  If the pigment was sitting in the seams instead of on top of the seams, I think I wouldn't have had to do as much (or possibly any) blending on the surface with paint and pastel.
  • I would still cover everything with a coat of Mr Super Clear.


If all that didn't work and I did it a third time, this is what I'd try:

Some Blythe customizers have used plastic shavings dissolved in acetone to create a putty that they use to build up areas.  The acetone evaporates, leaving the plastic solid again, working a lot like Plastic Cement.  The same method might be usable to fill gaps in Cortex instead of Mr Base White, though customers don't have an easy source of extra plastic.  Inside the bust, the pieces that you cut out could be used, but I don't think it would be enough to fill all the gaps.  By the time I did 3 dolls though, I'd probably have enough scrap plastic bits!


Final thoughts:

I have mixed feelings on Cortex.  It was the most enjoyable model I've ever assembled, and it needed far fewer adjustments than any other model I've worked on.  It's really well engineered, and comes together both aesthetically and functionally.

As a doll though, cortex is lacking.  I'm not even talking about the seams.  She could be totally seamless and she'd still fall short compared to both her vinyl and resin counterparts because of the soft plastic used in the shell. 

If you've handled one, you know exactly what I'm talking about.  If you haven't, let me put it this way: in Danny's video, he smooths down bent plastic bits on the shell with his soft cotton rag before assembling.  The shell is literally soft enough to be dented from rubbing with a cotton rag. Dressing causes scuffs.  Handling causes scuffs.  EVERYTHING short of 'looking at it' causes scuffs.

To prevent staining, I can pop on some stain protecting underclothes on the vinyls and not have to worry about it. Scuffs...?  MSC wears off, attracts dirt, and over time can discolor.  Plus, aerosol sealants aren't fool-proof: if the temperature or humidity is slightly off, it will dry with a white film. It's not a great solution.  Neither is having to use a sanding sponge every time I touch/pose/dress her.  The plastic is pretty thin already, and a sanding sponge will only wear it down more every time it's used.