Large Scale Central

Now to make your own Cut Quarry Stones

Start of Mik’s 2017, and first day of construction. As I had promised young Devon, I would teach or show you all what and how to make your own cut stones.

Of course the end products are cast resin from RTV silicon molds. This is how I do it! It is not the only way, I’m sure, but this is what I took away from Ray Dunakin’s postings.

I cut my masters ( that I cast into the RTV Silicon molds) from 3 mm Sintra board. Why 3 mm cause thats what I have, and I wanted them to be not to thick as they were to be a veneer and not stick out to far from the base that they were mounted on. Any thickness that you have will work, use what you have.

Stones and bricks come in all sizes, but most all are 1:2 in ratio of height to width. This allows for offset of the courses and stacking. It also allows for the making of patterns when laying, such as herringbone and basket weave. Working with the 1:2 is the easiest. Also needed are 1/2 blocks and 1/4 to allow for fitting around things like doors and windows. The smaller sizes are also used as architectural highlights to add design elements into the stone work.

Let’s get started. I picked a size of 1ft x 2ft in 1:20.3 scale. I started by setting up my mini saw to rip long strips to the correct 1ft scale size.

Cut more then enough, The set that I cast had 75 pieces in it, some of all sizes. You don’t want to be casting a lot of sheets of only a few stones, so cut plenty of strips.

Now for the actual carving, I use a very cheep little carving gouge that I picked up somewhere over the years. I have seen these sets some times in Harbor Freight, and craft stores. Cheep is the thing here.

What we want to do is take little shallow nick cuts all over the entire surface of the long strip that we had cut.

Random is what we are looking for and small little nick cuts.

Do this for the entire length of the strips, Make sure that you cut from all directions by turning the strip around, and work from both ends, Again what were looking for is a total random pattern. Don’t be afraid to cut some deeper then others and to nick and cut down the sides also.

I have found it most helpful to just keep cutting away on the strips, It makes a bit of a mess but a TV table and a good movie work well together.

Once you have as many strips carved to your satisfaction, then we need to cut them down into individual stones. I set up my mini saw to cut to length by marking to the desired length with blue painters tape, and then cut to length. The full stones, and the 1/2 stones along with the 1/4 stones can be cut from the same strips. I also made a couple of extra long stones for window and door headers. You will be best served for the long 1/2 blocks to cut narrow strips and carve them by themselves.

After cutting the individual stones, I then go back and dress the cut ends with several cuts and nicks to make them look like the sides.

So Go Get Started, Lesson two will cover some added detail stones.

Many thanks for showing us your method of creating your master stones. Coincidently, my wife gave me a resin casting kit for my birthday last week so I will definitely try my hand at this.

Great Dave. I did make a mold of your stones so they will match. But this is a good technique and I will likely make some from the start.

Day Two:

Today we will make an embellishment or two. My 4/4 window is not the same size as any combination of standard stones, so referring to a window treatment that I saw on a stone house in NY, I made a surround that will highlight the window and size it out so a standard row of stones will fit around it without having to be cut to size.

I sized my Sintra to fit around the window with two sides and bottom and top, so that when added to the window opening they will fit the standard course of stones. In this case 2 1/2 stones wide X 7 stones tall.

Now to make a bit of embellishment, I want to add a keystone in the cap, and a pit stone in the bottom, the sides I will let be. I drew out the keystone on the cap using radical lines from the center point of the window. And just put a pit that looked pleasing.

I want this window treatment to stand proud of the rest of the wall, so it needs to be thicker to stand out. I doubled up the Sintra on all pieces. I then cut with my razor saw the kerfs between the stones so I knew where to nibble down what was to be the stone edges, I did the same on the bottom piece and the pit.

Working on the carving, as if each stone was a singular piece.

Note: I dirtied them up to show the carving.

I also wanted to make a round porthole window as used as either a vent, or a skylight. Used about the same technique.

After carving all the stones, I then cut the double layered window in half to remove the center section with the saw.

After separating all the stones, I added yet another 1/16" piece of wood to the bottom of the 4 keystones, to raise them up a bit more to have them stand out from the rest of the pattern.

Trimmed them up and Wahoo…

I really liked the added look of the raised keystones, So I did the same to the keystone on the window and the pit stone also, sorry no photos…

I also added the extra layer of Sintra to a bunch of standard stones to achieve the raised look for added architectural interest.

Ray D. would achieve the same effect of the raised stones by adding a built up layer to his building, and use his standard stones. I hope to achieve the same effect, without having to build up the underling building. I will have to cast additional pieces of the thicker stones.

Tomorrow we take the stone masters we carved, and make a mold box for casting the RTV Silicone mold, and cast the mold.

Dave…help me out here if you would…where do you buy Sintra? I like this carving you’re doing and it might work for me. I’m not real happy with what I’ve done in stone using insulation boards, pink, blue, or otherwise. I think I kind of know what Sintra is, but I’ve never seen it sold anywhere?

Ask at local sign shops for scraps of foamed PVC board. Comes in many thicknesses, 3mm, 6mm, 12mm, 19mm and 25mm. If that fails I can send you small scraps for the cost of postage on a flat rate priority mail box - you choose the size box and I’ll fill it.

or look in the ‘junk box’ you won from Dave 2 contests ago … Thanks Dave!(

Once it stops raining I can determine the Arch that fits.


Very cool Dave.

Lets make some molds! We have our masters ready, that we want to replicate.

Here are a few thoughts on the actual molds that we need to make:

1: The RTV Silicon is relative expensive, so we want to use only a much as we need to make a good mold.

2: The mold box can be made from most anything, wood, cardboard, plastic, even Legos. The Silicon pretty much won’t stick to much of anything, other then to itself. But it should not be too porous, as it may be to hard to remove the mold from all the micro pores.

3: When laying out the masters, you should leave a Minimum of 1/4 inch or more from the edges of the mold to the master. This will give the added support needed to keep the mold from deforming under its own weight. IF the Master is deep, you need to increase this size. If your mold material is very flexible (soft) you will need to increase even more, or you will have to make a box to support the sides of the mold when casting.

4: For a simple one side mold ( as we will be using here) you need to have also 1/4 inch of mold minimum under the bottom of the cavity your casting into. Which is, that the mold box needs to be taller by 1/4 inch then the highest point on your master.

5: When you lay out you masters to make the mold, side proximity to each other is depending on the depth of the master you will be replicating. Very thin castings can be placed closer together, and thicker castings need to be placed with a greater spacing. This allows removal of your castings without tearing the mold, an if the original is textured or has a complex shape, or has undercuts, the greater the spacing the less chance of tearing the mold. Again, if you are using a soft silicon you will need to increase the spacing even more. The softer the silicon the easier it is to tear. Added thickness allows greater stretching before it reaches it’s tear point.

How big of a Mold Box do we need? I take the masters and lay them out on the table, and arrange in some kind of order, using the guide lines above, until I get what I think is the most compact layout.

I then measure the size needed for the base including the required side clearance for the depth of the master I’ll be casting. When I make my mold boxes, I have found that cutting the base to size, and adding the side boards to the side of the base works well for sealing the box, and for removing the finished mold.

I use 1/4 in “Masonite” type composite board, with the glossier side up. For regular wood bases, Sand to smooth, to help with mold removal, and if in doubt give a light coat of clear poly to seal. I cut to the desired size for the base board. This gives me a good firm stable base to work from.

Arrange the masters on the base board to the desired layout.

I use “Rubber Cement” to attach the masters to the mold. Using the rubber cement allows me to remove the mold from the box, with the masters embedded in the mold. I prefer this as it allows for the careful removing of each master individually, which is most important if they are complex or heavily textured, and difficult to extract. It allows you to bend the mold to assist in the release of each master, and not put excessive pressure on any one point while removing the mold from the box.

Once the masters have been glued down on the base board, I then measure the height of the side boards, making sure to add the minimum needed for the thickness of the mold above the master.

I attach the cut down side boards in an overlapping at the corners. I use my trusty pin nailer to put a few pins into the base board and into the corners of the sideboards. If you don’t have a pin nailer, you can use your rubber cement to glue the edges and corners to provide a good seal, and then duct tape it all together. Nothing real critical here, you just don’t want your expensive silicon to escape, and you do want to have a levelness to the top of the side boards.

You’r now ready to pour your mold…

Dave years ago I made molds using a liquid latex product. Baking the finished mold in the oven vulcanizes the latex and makes it extremely tear resistant. Is there any procedure, like that, for making the silicon molds more tear resistant?


I don’t know for sure, if that product is still available. What we are now using is called RTV ( Room Temperature Vulcanizing ) because it does not need the heat to set up, as it is a chemical reaction, and not a thermal reaction. I don’t know if low temperature ( < 400 degrees F.) would have any effect on the Silicone. I do know that there are about 1000 different formulas of RTV Silicone, And there just might be one that benefits from a thermal assist. I do use a formula that is rated for up to 700 deg. F, for casting low temp metals. But it is not as soft and pliable as the regular RTV I use, but really tough and the molds hold up to repeated castings way much better. It is a commercial product, and about 50% more expensive.

Dave, do you still have pictures for this MasterClass, and maybe a follow up on how the stones are holding up?

Bill, I wasn’t aware that all the pics have lost their links, I’ll see what I might be able to re-link…

Thanks for the heads up…

Dave T.

I second that it would be great if you could resurrect the pictures. I am new to G scale and am enjoying reading how to do the many different modeling techniques. I would love to build a stone house. Your efforts are greatly appreciated. Mark

Fantastic MasterClass Dave!

The pictures added a lot and your instructions were quite clear and concise. Could we have a glamour shot of the building you made with mouldings?

I do like Bob’s proposal to have a MasterClass near the other solstice.

LSC. Come for the classes. Stay for the banter

This was my Mik build in 2017…

That turned out quite well.
What sort of paint did you use on the stone?

Did you make your goose neck light or is it a commercial product?

I have some dye “Colorants” to mix into the resins.

AFTER: several years in the NM sun, I have noticed that the color has started to fade…

I recommend painting the stones…

Yes I turned the light myself.

Dave, I don’t think I’ll be able to catch up to you!

Thanks for getting the pictures back. I thought you were casting the whole wall and not individual stones, the pictures cleared that up. The resin, an epoxy ? Glue the stones with epoxy? The lamp is very cool.