Today’s adventure is cave tiles made from expanded polystyrene foam. I’m going to take the time to apologize for the lack of pictures on this post. It was kind of a last minute decision to make it.
I start out by drawing my basic shapes on the foam and get it all laid out. I don’t usually have a specific shape in mind for any individual piece, but by laying them out I can get a sense of how to shape things as I go along. Doing this also keeps me from being limited by space restrictions by the board dimensions.
The next step is to cut out your pieces. The most useful knife to use here is an extendable break off utility knife. Make sure you have a fresh blade, as a dull blade (even a slightly dulled blade) will tear the foam rather than cutting it. To be fair, though, sometimes that torn look can add an element that you can’t get otherwise.
At this point you can shape it down with the knife if you want, adding a bevel to the edges and carving or scooping out gouges for a more rock-like look. I usually just bevel the edges and do the detail work in the next step.
Now I take some kind of heating element, a heat gun or some sort of fire spewing device (a blow torch, a dragon, or if your boring a lighter) and lightly go over it to give it shape and definition. I have gone to using a heat gun, this creates an interesting formation with the foam as it seems to make individual balls melt more rather than whole sections.
You could also take this time to make valleys and specific craters or what have you in the foam. Once that is done (depending on the method used) you can go straight to painting using craft store acrylics (my process outlined below), or you can cover it with patching plaster. I recommend using the plaster if you are going to take a heat gun to it as the effect of the heat gun makes it difficult to paint on its own. The plaster will take a few days to dry. (Note: this is not the strongest substance so I do not recommend trying to crush it)
Once the plaster is dried to your liking (I gave it about a week) you can go ahead with the painting process. (Note: if you water down the paints it will get into hard to reach places better and will make your paint last longer) I give it a base coat in black, then go over it with whatever you want the main color to be (I like my caves to be dirt colored) with a heavy dry brushing. The number of coats can be whatever you feel looks best to you. I had to do two on these because the brown and black were so close. Then I did two coats with a lighter shade of brown using a less heavy dry brushing. I finished this part off with a typical dry brushing with a light brown that matched my scheme best. I would like to add that when I do my dry brushing for highlights I always stroke from the top down, it makes the most sense to me to do it this way, and as long as you are consistent with all your pieces it will look good.
The final stage is something that I borrowed and adapted based on the materials that I have, from Black Magic Craft. He uses a spray on lacquer finish, but I don’t have spray on so I use the brush on stuff left over from my woodworking that I had to put aside for the time being. I can’t say to any comparison here because I don’t know how the spray on ends up but I am satisfied with my current results. Anyways, enough rambling, I apply a coat or two of this stuff, usually using the satin to keep the glare down. In the future, I plan to add a coat of matte finish paint to break the glare down even more. I will put up a small post for that later to let you know how it turns out. Give it about 24 hours to dry and then you can start playing on it.