Quick and dirty method for making decent custom terrain bases in 40k. Alright so here is what you are going to need.
-A pair of latex or rubber gloves
-a tub of drywall Spackle
-a putty trowel or Spackle spreader
-a cheap large tip brush (the kind you get in a pack of 5 for $2)
-a generic matte brown acrylic paint (I used reaper master series)
-dark gray acrylic also matte preferable a cheap kind (I use Formula p3 Greatcoat gray)
Alright first off you will want to move to your garage or outside since this stuff gets everywhere, usually you can clean it off once it drys but if it gets on furniture or carpet its going to be a task cleaning so just best to do it where you don't mind a mess.
That being said you'll want to open the tub and hold your base in your other hand, or you can hold it in place on the table while you dig out a finger full of Spackle, now judge how much you think should be used by eye, if you want a little platou you'll want to glob a bit more in the middle, if you want more or less average ground a big finger full of the stuff should do, adjust amount as needed.
Now you will want to spread the glob of Spackle out evenly with the drywall trowel, don't worry if it looks to flat, now with your finger dab at the smoothed layer until its got a little less smooth. Now this is the part where I recommend the artists sponge cause its an easy way of texturing the wet Spackle, just lightly dab the sponge on the Spackle until you see a good even grain/texture. If you don't have an artists sponge you can use a cheap bushy tipped brush, just dab and roll over the layer and use it to push and mold the wet Spackle into any shape or foundation you want.
Before letting it sit to dry take the model you will be placing on it and gently press the base of it in making slight indentations. This is an optional step but it will help greatly when its time to glue the models onto the base.
After the Spackle has dried chip or sand away any loose Spackle on the edges of the base and use the same texturing brush to wipe away any dried loose Spackle on the top, you do not want any dust to accumulate of the sealing primer layer wont harden right and it will chip.
Now that you have cleaned up the base simply take it outside/to your painting area and give it a good primer making sure to get a complete coat, make sure there is no white spots remaining cause it will stand out or chip later on. I use black primer because I make muddy dirt bases but I will tell you an alternative way to make snow/ice bases at the end of this tutorial.
After waiting at least 30 minutes for the primer to dry and seal the Spackle now take that same bushy tipped brush (after washing the Spackle out) and dip the better part of the tip in your gray acrylic and just roll it over the Spackle layer, don't press down to much but make sure everything has a good even coat and try not to go over the edges. After that's dry do the same with the earth/brown acrylic but don't use as much as you did with the gray just enough to cover and only lightly roll over the edges, this will make it look like a mushy clay/earth color and contribute to the aesthetics of the piece.
After everything is dry I like to add just a light layer of black wash, again this is optional but it will add some tone and shadow and fill in any cracks that might have developed when drying. After that a little bit of glue on the contact points of your models and then position them on the base, some glues might slosh over a little bit around the edges of the contact points, simply apply a little bit of that earthen brown or gray on these spots and it should look ok.
All you need to do is use the artists sponge to flatten and texture the Spackle, then switch out your black primer for a matte white primer. After that drys brush on a generic coat of acrylic white paint, then when that drys use a light blue wash and just gently apply that over the textured surface and around the edges. I have not tried this variation yet but if you do please let me know how it turns out and maybe send us some pictures.
The beauty of this technique is that the foundation material is so pliable and versatile not to mention cheap that you can really do what every you want with it depending on what base colors you use and how you shape it. Indeed you can easily add all manner of flocking be it gravel, sand or greenery and be assured that it will hold, you can also add bits of rubble or little metal plates, as long as you have a good sealed primed base there really is no limit to what you can do with this stuff so toy with it and let me know what you come up with.
BH Senior Editor