I mentioned a coupla weeks ago that I'd try making inexpensive synthetic stucco and that I'd let you know the results. Well, punctuality isn't my strong point, but I finally got around to experimenting.
Synthetic stuccos like I mentioned are glorified heavy latex exterior paint with a lot of sand mixed in (and various hardeners, etc). I mixed some exterior paint with silica sand and a little tint to make it show in a picture better, and it worked pretty well. I just spread some on an old Styrofoam cooler for the pics. Click the pics for the larger versions.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/StoneCap0001.jpg http://i36.photobucket.com/albums/e31/pjhawke/revenant/StoneCap0003.jpg
Mixing the stuff is easy. You know the consistency of sand-finish paint? That's not what you want. You want to keep mixing sand in so that it's no longer fully liquid anymore; you want it real thick and slushy like wet cement or thick oatmeal.
The right-hand side was my first try. I didn't trowel it on or use a putty or taping knife, I just sort of spread it around with a wooden stick. As you can see, it was too thick a coat, and it sagged and drooped a bit. Which might be an effect to go for if you want a poorly done cement job look. Or the Incredible Melting Gargoyle or something. The latex paint just doesn't have the viscosity that the syn-stucco stuff has to hold the weight of the sand. The side on the left was much better; I used a trowel and putty knife to apply the stuff very thin so it wouldn't sag. Nice flat surface; could be cement stucco or concrete, could be unpolished cut granite or limestone.
http://i36.photobucket.com/albums/e31/pjhawke/revenant/StoneCap0002.jpg http://i36.photobucket.com/albums/e31/pjhawke/revenant/StoneCap0004.jpg
You see above the nice sandy surface, flat but still not smooth. At a fraction of the cost of the stucco stuff. Light will diffuse over the surface and soften the shadows just like on stone. When the paint dries, it shrinks a bit and pulls back, exposing the sand grains more. You can enhance that by taking a damp sponge and LIGHTLY patting it over the surface, it removes the extra surface paint and exposes more sand. To eliminate trowel lines, just give it 15-30 minutes to set some, and lightly scrape a putty knife along the lines to flatten them down. Be careful to keep the edge of the blade completely parallel to the surface or you'll just gouge new lines. Rounded corners are tricky, you'll probably have to go over them a few times; the damp sponge trick helps with that too. And you're better off with silica sand than brown sand; silica sand is colorless (ranging from white to light grey), other sand will add its own color, appearing brown or even pinkish. If you want something to look like limstone it would blow the illusion.
I'd probably do this at least twice on my faux stonework so I know it has a nice thick protective coating; obviously, you needn't be so precise with your surfacing on the undercoats. It keeps water out, and adds impact and abrasion resistance. Go to the drywall section of your hardware store and get several widths of taping knives for your spreading; several from 1" to 6" are nice to have. They usually have disposable plastic ones for a fraction of the cost of the real ones, so if you're just going to use them for your tombstones or whatever and not real construction work you could have a full set for the cost of one good one. If you plan on doing something big, like a mausoleum, do yourself a favor and buy a real plasterers trowel, it will save you tons of time.
Hope this helps somebody.
