With all the sculpting that I do, I've developed a way to turn simple cardstock into plasticard and make a very sturdy base for me to sculpt on when I need it. Using plasticard and greenstuff is an art. Some folks do it better than others... I'm not one of those and that's how this trick came about.
I've been asked before how I do this particular thing and I figured it was time to show exactly what I do to make the change from cardstock to plasticard.
You'll need two things
Cardstock and Superglue
When it comes to cardstock, I prefer the simple stuff like a regular index card. You can use posterboard if you want, you just need to make sure it's not the glossy kind or that it has any kind of coating to it. You want the stuff that will absorb liquid.
As for the superglue, I use the cheap stuff myself. The trick though is getting a kind that is like water. You want it to be very runny and nothing like a gel. You want to be able to apply it to the cardstock and have it be absorbed into it easily.
What I use this technique for
While I'm sure there are more uses, I tend to focus on just a couple of things. Purity seals (the long flowing kind), and support structures for when I sculpt things like tabards. Those are the two main things.
I also use this approach when I'm building armour plates like my Pre-Heresy Terminator shoulderpads and greaves.
How it works in practice
In the case of things like purity seals, I simply cut out the shape I want, bend it into position carefully and then attach the piece to the model with a tiny drop at the connection point. Once it's secured, I go through and "coat" the cardstock with superglue by adding a few drops here and there and allowing them to absorb into the cardstock.
When it comes to tabards, it's the same thing. Cut your cardstock to shape, attach it to the model and then coat with glue.
I usually only coat one side of the cardstock and that's the side I'll be applying the greenstuff or any paint to. The other side is left alone. It can still be worked on since the glue has soaked through the cardstock and solidified the whole thing.
What to be careful of
The big thing is applying too much superglue. This only matters on things like the purity seals since too much superglue will dry and once the cardstock has absorbed all it can, the rest will pool up on the surface creating unwanted texture.
In the case of half tabards, it doesn't matter since you'll be covering the whole thing with greenstuff anyway.
The second problem comes when you rush the drying. Don't mess with the superglue as it's drying or you run the risk of pushing it around on the surface and creating waves of texture. The idea is for all the glue to absorb and leave a smooth surface you can work over it without having to worry about the water in your paints affecting the cardstock underneath and eating away at the stability of your model.
And there you have it, how to take regular index card (cardstock) and turn it into "plasticard" so that you get the rigidity and support you need in the end while keeping the flexibility and ease of working with cardstock in the beginning.