I don’t do carving of the sides of my foam rocks. I will stack them to get more elevation and then coat them with a Gypsolite slurry and other scenic material, including plaster cloth, depending on the effect I want. Because once it’s glued down it has no mechanical stresses, I find that white glue works well enough. I do give it several days to harden because the foam sheets seal together tightly and it takes a while for the glue to get enough air to dry.
I have a lot of hydrocal castings I use for vertical cliffs, and I really like Bragdon Foam castings for up-front scenes I want to highlight.
The Bragdon castings (and his method) are fantastic. I chose them because I was building a layout that required me to work alone and climb up on the benchwork and his method/products allowed me to put up 2’X2’ castings that weighed only a few ounces!
The molds themselves are high quality latex like Hollywood uses for masks, etc. and Bragdon was a geologist so his molds are very realistic and regionally specific (granite, sandstone, whatever).
I don’t have photo sharing abilities here but there should be examples online. I personally think they’re the most realistic molds around.
I’ve found that as long as I don’t leave an “air hole” in the tip of the nozzle, the caulk tube will remain useable for a seemingly endless period of time. When done with the project-at-hand, I’ll give the caulk gun handle a few light pumps, until the caulk in the nozzle doesn’t get sucked back into the tube. At the end, I’ll use my finger to smear the last blob of caulk across the nozzle tip, making an air-tight seal. When the caulk is needed again, some forceful pulls on the trigger will push the hardened blob out. If not, cut a small amount off the nozzle (1/4") and try again.
I used to leave a small lump of caulk on the end after doing my work, pull that off and it was still good six months later, after about a year you would have to dig it out some or cut off more of the tip. I always use the stuff pictured, used to use by the case in the old days.
To seal a partially used tube of caulk, I stick a 16 penny nail into the tip of the caulk tube all the way down to the head of the nail. Then, I twist a small piece of Saran Wrap around the tip of the caulk tube and secure it with a rubber band. The remaining caulk will remain usable forever.
