Okay I am going out on a limb here for the challenge build. So far for the indoor my rocks have consisted of carved foam only. In HO and in N I used foam bases (among other things) and glued on plaster cast rocks which I made using latex rubber molds. I was all set to make some plaster castings of basalt columns using latex molds I made from masters my friend Dick Whitney made. I have the molds all made up, there are three masters and I made a mold of each. I just figured I would do what I have always done and cast them in white plaster and paint them. Then I was lying awake in the middle of the night thinking about this and started thinking about how to dye plaster. It would sure be nice to start with a black or very dark grey base. This led to powdered concrete dye which then led to the big bag of black sanded grout I had bought at the ReStore last year for a buck. I am, as I am typing, waiting for the first casting made with 100% sanded grout. I am worried it will be very brittle as grout really isn’t very structural. I figure if this fails I will try a combination of say 70-30 or 60-40 plaster to grout. Maybe even add some cellulose insulation for reinforcement if I need to get real crazy. But these are indoor rocks and are small 2-3 inches wide and maybe 5-6" tall so I am not thinking I need a bunch of over the top reinforcement. At 1:24 these will be small basalt columns. I think he was thinking O scale when he made them. But basalt can come in small coulmns as well as giant ones for this I think it will work nicely if I can get a good casting. In all else fails I will just go back to plaster dyed with acrylic paint.

The idea behind the sanded grout is to not only give it color but texture. Basalt is not smooth, it is . . .well kinda sandy feeling. So i am hoping I will achieve a nice looking base rock from which to work with.

I thought by the title you were going to use your foil hat to make fake rocks, that look like your noggin…,

I have plenty of “fake rocks” on the T&LB that live outside.

There are two simple ways to do this. The first is to make your rock out of styrofoam and alternately sift dry powered hydraulic cement and mist it. The cement will build up to a hard waterproof layer thant lasts outside for years. This also works to make structures.

The other is to just form the rock from mesh/chicken wire and apply a layer of masking tape to the outside. Sift/mist the cement into and onto the tape and you have a hollow rock that you can use to cover whatever.

I can tell you already this is a patience game. It is taking way longer than I imagined for the grout to set up and dry. Not sure what i expected really but it has been several hours and it is nowhere near ready to demold. I am thinking just for my sanity I will go with dyed plaster.

Less heat generated when it ‘goes off’ and you have it enclosed, so it only has a small area to degas, relax, you have weeks yet.(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

John Caughey said:

relax,

No

Devon Sinsley said:

John Caughey said:

relax,

No

Then fret.(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Acrylic artists paint seems to colour/mix plaster ok…take it easy tho…

Devon Sinsley said:

Okay I am going out on a limb here for the challenge build. So far for the indoor my rocks have consisted of carved foam only. In HO and in N I used foam bases (among other things) and glued on plaster cast rocks which I made using latex rubber molds. I was all set to make some plaster castings of basalt columns using latex molds I made from masters my friend Dick Whitney made. I have the molds all made up, there are three masters and I made a mold of each. I just figured I would do what I have always done and cast them in white plaster and paint them. Then I was lying awake in the middle of the night thinking about this and started thinking about how to dye plaster. It would sure be nice to start with a black or very dark grey base. This led to powdered concrete dye which then led to the big bag of black sanded grout I had bought at the ReStore last year for a buck. I am, as I am typing, waiting for the first casting made with 100% sanded grout. I am worried it will be very brittle as grout really isn’t very structural. I figure if this fails I will try a combination of say 70-30 or 60-40 plaster to grout. Maybe even add some cellulose insulation for reinforcement if I need to get real crazy. But these are indoor rocks and are small 2-3 inches wide and maybe 5-6" tall so I am not thinking I need a bunch of over the top reinforcement. At 1:24 these will be small basalt columns. I think he was thinking O scale when he made them. But basalt can come in small coulmns as well as giant ones for this I think it will work nicely if I can get a good casting. In all else fails I will just go back to plaster dyed with acrylic paint.

The idea behind the sanded grout is to not only give it color but texture. Basalt is not smooth, it is . . .well kinda sandy feeling. So i am hoping I will achieve a nice looking base rock from which to work with.

Devon in my HO days I made "soft rocks’ out of sponge rubber coated in a mix of fine sand (similar to what bricklayers use to make mortar) and water based acrylic house paint.

I formed the rocks by plucking pieces of the sponge to shape (very therapeutic in front of the TV) them dipped it in the paint the rolled them in the sand.

When dry the paint/sand formed a crust that was quite durable, the paint/sand that didn’t stick I collected and put it in a sealable container then added some diluted PVA glue I kept this moist and used it like grout to cover the joins in the pieces.

I have pictures somewhere of the old layout and you can see that I made walls about 4-6" high.

I also made my own “ground foam” using the same sponge put through a meat mincer then a blender, in the blender I added acrylic poster paints to colour the foam then once it dried I fluffed it up in the blender. I made heaps of “foliage” for only a couple of $. I still have some left over and may use it on my new layout that is planned to have an indoor section.

Devon I have attached a pdf of how I made my “soft rocks” out of sponge rubber back in my HO days.

Graeme Price said:

Devon I have attached a pdf of how I made my “soft rocks” out of sponge rubber back in my HO days.

Graeme,

Thanks for that tutorial. I am always looking for good ways to do new things. I will put it to use on the indoor for sure.

So the 100% grout is a bust. Not just because of my patience. After 24hrs I tried taking it out of the mold and it just crumbled as I figured it might. The pieces that lived looked awesome in color and texture bt just were so fragile. So I am on round two. I dusted the mold with the grout and then mixed 5 parts plaster and 2 parts sanded grout. Well its setting much faster so that’s good on my nerves. The color of the plaster is a lighter grey than I prefer but that will be as easy as adding black paint which I have done before. The texture is weak on sand but I can’t see yet the side in the mold to see if the dusting took hold and if it gives the right texture. If this one doesn’t work out it will be good old plaster.

The mold itself is great. The shape and the detail of the mold came through nice and will make great basalt formations.

Devon Sinsley said:

So the 100% grout is a bust. Not just because of my patience. After 24hrs I tried taking it out of the mold and it just crumbled as I figured it might. The pieces that lived looked awesome in color and texture bt just were so fragile. So I am on round two. I dusted the mold with the grout and then mixed 5 parts plaster and 2 parts sanded grout. Well its setting much faster so that’s good on my nerves. The color of the plaster is a lighter grey than I prefer but that will be as easy as adding black paint which I have done before. The texture is weak on sand but I can’t see yet the side in the mold to see if the dusting took hold and if it gives the right texture. If this one doesn’t work out it will be good old plaster.

The mold itself is great. The shape and the detail of the mold came through nice and will make great basalt formations.

Devon,

Email these folks in Southern California. Near me in North Hollywood. My friend and I, involved in building seven 1/8th scale Baldwin electric locomotives, needed to make a nesting mold to produce a pattern to make extra cast iron wheels for these engines. These are fairly simple wheels (about 5 3/4 inches in diameter) in most respects except they have nine spokes radiating from the center. There is very little draft on these spokes and we needed to remove the pattern mold from the master easily and NOT damage the master. Both of us are very familiar with making molds and the casting process. BUT we needed help in finding the proper “parting agent” to release the master easily. I contacted a movie SFX supply house near me (they’re all over this area) and they were able to provide the casting material and the parting agent we needed.

Here is the link: https://www.reynoldsam.com/la/

Reynolds Advanced Materials. They are not just for movie people, they deal with hobbyists all the time! The guy we dealt with about six months ago recommended the casting material and even calculated how much we needed to pour TWO pattern molds. Either phone them or contact by email. I am sure they will help you do this right!

Gary,

Thanks I am already familiar with Reynolds. They helped me with totally different process of cold casting metals in resin and then using chemicals to patina them. I have yet to put it to practice but they were very very friendly and helpful people.

With that said, this casting project is a very specific look. Basalt column rocks are prevalent in my neck of the woods. A generic rock will not do. My friend Dick was obsessed with basalt. And he made the masters I am using now. So the idea is to get a very specific look and texture.

Here is the base I came up with. This was attempt #2. Dusting the mold with grout and then the mix of 5-2 plaster/grout yielded what I think will work. Great base color and has a grainy texture. Some weathering powder and lichen and what not will make it perfect I think.

Went at it with some red weathering chalk and then glued on some ground foam. I am done playing with it until I can mount it but I think it looks good

Devon Sinsley said:

Went at it with some red weathering chalk and then glued on some ground foam. I am done playing with it until I can mount it but I think it looks good

Looking real good there Devon, that ground foam is similar to what I produced following the tutorial.

Another product I used to make stratified cliffs was the stuff used to make suspended ceiling, I just layered it then scuffed it up with a screwdriver.

I got the idea from a “model Railroader” magazine article. It was very heavy but easy to use and it could be molded when it was wet, it set like concrete.

I was lucky to be working on a building site during a renovation and they were throwing out tons of the stuff so I ask fro some and was told to help myself to it.

After a few castings a wall is forming. The three on the right are the different molds. Th left one is just some leftover plaster that made a nice shorter section.

Here is the end result. I am happy with this method. The texture is right the base color works and then the red weathering chalk adds that rusted look and the green and yellow ground foam make a nice lichen. BTW the red for those of you that don’t know is very typical of basalt. The main mineral in basalt is iron. And just like the real deal when exposed to air it rusts.

The basalt came out very well, Devon. The color and lichen add another level of reality. Good job.

Devon