Can I use the “plaster of Paris” I cast rocks with to blend them into the foam scenery or do I need to use sculptamold or something similar? My apologies if it’s a dumb question, new to the hobby and building my first layout. Didn’t realize how big of a learning curve it is 
No dumb questions, if you don’t know the answer.
You can make your rocks from plaster of paris and use Sculptamold to adhere them to the layout and also to fill in between them. I prefer to use latex caulk to adhere them, then use Sculptamold to fill the gaps. Made most of my castings from plaster of paris. I did use Sculptamold for a couple of large castings for large, curved “cut” walls, using tin foil for a mold, that I wanted to dry a bit slower. so that I could place it properly.
Some folks put either product on their layout and carve the stone faces into the soft material before it sets.
Good luck,
Richard
If you plan on using stains on the plaster rocks, they take up the stain differently than the Sculptamold. Best to use plaster to fill in between or plan on covering with some ground foam, for instance.
If you’re painting, it’s less of an issue. Once you have a prime coat over everything, you should be good. If not, try another coat.
Im painting all the “scenery” (plaster and foam) with flat tan first then was planning on acrylic washes and then adding ground foam in places
I am not completely new to this, but its been about 25 years and a lot has changed. So sometimes it feels all new to me too. I am working on terrain on my new layout (foam bits are flying everywhere!) and at the same time trying out new landscaping techniques on a test board. Getting advice here is very useful, but suggest you actually experiment and try stuff out before applying it to the layout. I learned a ton playing around on my test board the last few weeks.
For rocks my best results so far are actually using the same methods I used back then, but with a twist. The “test” rock face in the pic was done by applying wet plaster directly to the foam using tinfoil to control the shape. But instead of a hobby knife (my old method) I carved the plaster after it dried with a dremel using different bits to get different “effects”. Actually pretty quick and easy using the dremel. And then I colored it with acrylic washes, again trying out different color combinations to see how they looked.
Some things I learned as I went along:
Wet plaster sticks to carved foam pretty good, especially if the foam is rough. But it does not stick that well if the foam has already been sealed (painted) with regular wall paint.
If you paint the foam after applying rocks (whether gluing them on or applying wet plaster) make sure not to get any paint on the plaster because the painted plaster won’t “take” acryilic washes.
I also tried blending the plaster to the foam using Sculptamold for the first time and found it works OK. The Sculptamold can be painted along with the foam and it blends in nicely. But it will not color the same as the plaster if you use acrylic washes to detail the rock face. So be careful or you can end up with an odd color if you get too much Sculptamold on the rock and don’t use some sort of ground cover over it. I am still not convinced that Sculptamold is the bes
Our posts last night crossed. To clarify, staining rocks with acrylic washes really looks great, but it requires that the plaster not be painted first. And the trick (for me anyway) is how to do the blending so that everything but the plaster gets sealed with the tan base paint and there are no odd looking seams between the materials. It can be done using various methods- and there’s nothing like a little trial-and-error experimenting to develop techniques that work good for you.
I just got my first Dremel, what bits are good for this?
Matthew
I discovered dremel when building RC airplanes, also made extensive use of it detailing parts for car restorations. Now finding good uses for the MRR. I like the cordless, vari-speed version. My first cordless disappeared with my ex-son in law. My new cordless dremel is much bigger for some reason but still works the same.
The bits I use most often with a dremel are abrasive cutoff wheels, wire brush, tiny drill bit kit, and those that look like drill bits but designed to cut to the side (drywall cutter?) Also if you look at the accessories shelf you can buy a regular chuck to attach the bits which is much more convenient than the collets that come with the dremel kits. And the chuck is a necessity in order to use drill bits.
To do a rock face I apply plaster in sections using tinfoil. I crinkle the tinfoil first to give the surface some texture and shape and lift the edges to form a bowl of sorts. Then pour in the plaster. When it just starts to thicken up I apply it and press it into place. Give it a few minutes and pull the foil off as soon as the plaster begins to set, and then use an Xacto knife to blend the new section in while the plaster is still soft. You have to work quickly because the plaster hardens fast once it starts setting. This was always the biggest downside to this method for me- there is very little time to work in strata with the knife before it gets very hard to cut. So it always ended up taking hours to get it to look really good.
The new trick (for me) was the dremel. After the plaster was dry I used mostly a wire brush bit and a cutoff wheel bit to form the rock strata and crevices. And also to flatten the rock faces in places. Both of these bits cut through the hard plaster like butter but were pretty easy to control. Then just a little touch-up and scoring with an Xacto knife to add some detail. The idea is to work the strata into the basic rock shape that
Thanks HObby Guy
im doing N Scale and will have to do an awful lot of cutting with any of the commercial molds that I have sseen please post some of your aluminum foil castings
thank you
Matthew
The foil goes straight into the trash as soon as I pull it away from the plaster, so none are alike. Best I can do is take some photos right after the plaster is applied and then again after it is carved. I should be ready to start with the rock faces on my layout within the next month and I can post pictures as I go. This method looks like it will work best for sedimentary rock like in the picture, which is what I mostly need. Not so sure about N scale or other types of rock structures. Give it a try- it costs nothing except a bit of plaster.
Do you spray anything non stick on the foil? Matthew
To be clear here I am no expert at making rocks! The only innovation I have to share is the dremel carving technique (and I am sure I am not the first one to ever give the dremel a try.)
Using foil is a very old method that I learned maybe 30 years ago, and if you do an internet search you can find lots of variations. Here is a page from a 1971 publication that shows how I would do it for N scale.
http://d1ke3s7oc9e1xt.cloudfront.net/public/article/d4/d0/05/5c609_ba43.jpg?c=98b4
I don’t use anything as a release agent. The tricky part is knowing how thick to make the plaster and how long to wait for it to cure, but it’s pretty easy to figure out with a little trial and error. If you get it right the plaster won’t stick to the foil. Even if it does it’s not hard to dress the face with a knife as it hardens. I am never satisfied with the rock as formed by the foil and always get a few bubbles to carve out but for me it’s a good starting point to work with.
I use wet water, but I’m not sure it is necessary.
Also, I keep a crumpled piece of tin foil handy when I am pouring other castings. If I have a little plaster left over I pour it in. I can either use it as a small rock face or break it up for talus at the foot of a large rock face.
Have fun,
Richard
Our posts did cross, im glad I took a break from Working on the layout that night before I read the post regarding not painting the castings (was in the process of painting foam)
So far I’ve only used hydrocal and the consistency is closer to liquid than any sort of moldable material, am I mixing it too watery or is plaster of Paris less liquidy?
Matthew
None of the plasters are “moldable” like clay. I don’t try to measure the materials, just mix it by eye to a consistency that varies a bit depending on what I am going to do with it. If the surface flattens by itself then it is probably too thin for making rocks with foil so try using less water. I aim toward more of a cream consistency.