Scenic dope is a general term for a number of materials used for a number of techniques. In the late 19th and early 20th centuries, a ceiling paint known as calcimine was popular. It was essentially whiting mixed with animal glue and a bit of water. Whiting is powdered and washed white chalk, aka calcium carbonate. Set builders used it to prime flats for painting, or a thicker form to adhere muslin to flats. Along the way, it evolved into recipes and formulations which could be used for all sorts of texturing.
If you add linseed oil to whiting, you can make a simple caulk. If you mix whiting with casein (milk protein used as a binder in casein paint) and water (and borax if you want anti-fungal qualities) you can also make a simple joint compound. With the introduction of latex paint (really, acrylic paint, as it contains no actual latex), we now have the modern equivalents for the building blocks of scenic dope.
As it is a material which undergoes frequent experimentation and improvisation, no set recipe exists. A good place to begin your own experimenting is with a gallon of latex paint, 2–5 tubes of painter’s latex caulk, and 1–2 cups of joint compound. The thinner recipes (more paint, less caulk and joint compound) make good coatings for foam, while the thicker recipes (some push the ratio to equal parts paint and joint compound) can hold some heavy texture as it dries, almost to the point of being sculpt-able.
Note that the recipe calls for latex caulk and not silicone caulk. Silicone caulk is more common and easier to find in hardware and home improvement stores, but silicone does not bond with anything, which makes it impossible to mix into a recipe.
For a more flexible recipe, you can mix joint compound with glue (animal, or PVA). This is especially helpful when you are coating surfaces that have a bit of “give”. The harder dope recipes may crack under strain, whereas this one will bend.
You can add any number of additives to your recipe. Water putty and plaster allows it to dry harder but more brittle. Paper pulp really thickens the mix, and it can become almost like a thin clay, which is great for sculpting bark or rough stone on your surfaces. Sand can be added for a, well, sandy surface. Really, if you want a chunky texture, you can add almost anything chunky that you have laying around. In addition to mixing materials like sand into the mix, you can also sprinkle or dust it onto the surface while the dope is still wet. This will give it a coating, or crust, that you may find to your liking.
Theatrical suppliers make any number of products which mimic scenic dope, each with slightly different properties, but formulated to give consistent results. Rosco’s Foamcoat and Sculptural Arts’ Sculpt or Coat are just a few.
Because the recipe consists of latex paint and joint compound, both of which are water soluble, the resulting surface needs to be water-proofed if it will be outside or around moisture.
The properties of dope are similar to the wheatpaste used in papier-mache, and it is frequently used in conjunction with fabric. Strips of fabric are coated with dope and lain over a surface to create textures.
“Monster mud” is a term which began to appear in the late twentieth century to describe a mixture used frequently in the haunted house industry. You mix five gallons of joint compound with one gallon of latex paint. You can then submerge cloth—a large weave like burlap works best, though clothing or other fabric works as well—into the mixture, squeeze the excess mud out, and shape it. You may also spread the mud on straight to add texture. It may take up to several days to dry, but it becomes rock-hard (though not water-proof). It’s a clever way to mimic sculpted fabric, though any kind of flowing surface lends itself to this technique.