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The O Gauge Railroading On-Line Forum Scenery Ideas and Techniques Rock mold application to mountain?|
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I have seen two ways to make and apply rock (plaster) molds to the terrain. One is pour plaster into mold....let set completely and cement into place. The other method is to pour plaster into mold...wait until there is a slight sheen to surface (partialy set) then lift mold into place and let set...then peal mold free. I am working on my largest and last mountain and wondered what method I should use. Up until now I have let the plaster in mold set, removed rock form and used plaster to cement into place.
Steve Texas on the West Coast........  |
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I let it dry in the mold completely, then spray the rock and the spot on the mountain with some water and then put on some slightly thicker plaster to both surfaces...hold it in place for a few moments and tada.....got it from Rich Battistas DVD...works like a dream...
 Chris W. Don't call me irrational you know that makes me crazy!!! |
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I agree with Chris and Gizzmo.
I've never had any luck with the still-soft method. I always wind up leaving half the rock face in the mold. Maybe it's because I usually use plain, cheaper, plaster of paris instead of Hydrocal. Another reason why I like to use completely dry castings is that I can arrange them, look at them, rearrange, break pieces off, re-rearrange, etc., etc. If they are still soft, when they're down, they're down - no moving possible. Jim |
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I always pre-form my rocks, as well.
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I concur w/ the above. I precast - trim as necessary, position and then hot glue in place. They have to be good and dry for the hot glue to hold.
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Some other options are..
Using cured castings hot glued to plaster cloth sub base (ala jig saw puzzle) and then castings are grouted together with Sculpamold. This was the method used in the valley portion of this picture. The upper portions of the mountains are Sculpamold hand formed over plaster cloth. With both methods the medias were pre colored with mortar pigments and then sprayed with additional solutions of mortar pigments for texturing after it was dry.  See more at: http://www.tuveson.com/updates/updates.htm Carl |
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Jim, I tried the mold-in-place method with hydrocal and got the same poor results. I doubt it's the plaster you're using.
Steve, I've had some excellent mold-in-place results with Bragdon's foam rock method. After it's no longer tacky, you get as much as 30 minutes to form it in place on your scenery shell. Just peel it free of the mold, then press it up onto the shell, pushing it into the shape you want it to take. Yo can glue it in place while it's still warm and let it harden in place, or prop it into place with sticks and stuff to le it cure, or just keep workin' it til it firms up. You can make custom pieces by shimming under the mold here and there, and by molding it around without gluing it down. I even had good luck making a cradle for curving a 5x23 mold 150 degrees around a 38-inch diameter form... inside curve and outside curve. Last weekend I cast up & shipped off to my Dad 26 rock faces totaling 30 sq ft, half of it custom-formed to be assembled in place. |
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Steve, the AGHR layout uses both techniques. The pre-cast rocks seem to work best if they are being applied to a relatively flat contour, that is a smooth base on which to apply your castings regardless of the angle of the terrain. Gizzmo's tilted strata rock work is striking in its perfection. Our club members don't get geology. Everything is horizontal. We make our rock castings out of hydro cal using commercial and home made molds. The casting are as hard and strong as rock. The way get a controlled break is to scratch a line on the back of the casting before it gets hard. We get straight breaks that will mate with the bench work, simulated water in lakes, and structures that require a straight line, as behind the trestle bents on Dave and Mikes trestle The large castings that don't mate well with the base layer of the terrain we back fill with hydro cal of joint compound and texture with wrinkled aluminum foil
The AGHR layout has some pretty tortured terrain. We position the molds on the base layer of the terrain looking for the best fit. When satisfied we spray the mold and base with wet water, fill the mold with hydro cal, wait for it to start to thicken and slap it into position. It might be necessary to hold the mold and hydro cal in position until the hydro cal has started to cure. Could be several really boring minutes. Any mush out is textured with wrinkled aluminum foil. Well, that's my three cents. Howie Sorry I don't have any pictures. The fourteen steps to get photos on the post are over my head. I deal only in free form mud slinging. |
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First of all......thanks everyone for the responses....Chris, Gizzmo, Jim Vulcan, Deang, Carl, Bob and Howie.
I used the "let plaster dry" method on my first part of the layout but my areas of applicaton were fairly small. I am doing a large mountain this time and have a couple of large laytex rock molds....so I thought I would try attaching the mold while still flexible. Howie...I did not get your post when I tried doing the soft method....I built up a dummy mountain (small) and when I tried to get the right drying time to put the mold on...most of the plaster oozed out. I tried several times, but could not get it right. So I did my large rock molds...let them dry and used the tip to make a line in plaster while still wet....and will break apart and apply. Bob...I tried Bragdon's foam molds on club layout, but could not get the right color or use paints I wanted to make my rocks look real...thanks for the tip though. Some of this new tech scenery stuff I can master...but this one thing I failed at.... Thanks again......  Steve Texas on the West Coast........ |
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Steve, I just clicked on the link on Carl's post, and got an eye full. You can't argue with success of that caliber. What Carl, Gizzmo, and other have created and have posted photos of, to show us the possibilities, requires the creation of new word to describe the mastery of the art of model railroad scenery craft. AMAZING and STUNNING are inadequate.
Steve, the AGHR layout is a committee project and looks pretty good anyway. We have had our problems with both cured castings and wet applications. They have added to our vocabulary of colorful words. We use joint compound to apply the cured casting to the scenery base, and wrinkled foil to texture the the joint compound on gaps, bad laps, and casting edges. Hydro cal starts to set in about five to seven minutes, maybe. When the hydro cal gets viscus when you tip the mold, that may be a good time to slap the mold on the base material. Support the low side with your hand and have some wrinkled aluminum foil ready for any leaks. AGHRMATT has photos of our techniques and results. Steve, anyway that works for you is the way you should go. Howie |
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Howie.....the AGHR layout site was super! How many helpers do you have? My work force consists of ME! I'm glad to see that I did my mountain support like on the AGHR with cardboard strips with plywood supports to tie into. I also used plywood portal backings. I was thinking of placing my portals in-place after all the rock work was done...but I see the AGHR glued them in place prior to this being done. I wanted to protect my paint work during the dirty part of rock and plaster. I guess I can place them and tape over them to protect the paint job. I am not going to have as much rock as the AGHR because the terrain in Texas (hill country) is partial rock and grass lands. But I have pre-made enough to make it look real. I do appreciate all your kind help and reference to sites which provided me with so much info.
Thank you again everyone.... Steve Texas on the West Coast........ |
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This picture gives me some great ideas. I am struggling with how to build the mountain give my compact track plan. Thanks! George |
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Carl, beautiful layout and scenery. Neat and well organized, Great scinic technique.
Don |
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Thank you so much I been given so much from everyone on how to do when I start my layout it will be fun
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