How do you----???

Discussion in 'Scratchin' & Bashin'' started by XavierJ123, Apr 8, 2005.

  1. XavierJ123

    XavierJ123 Member

    How do you build plaster of paris piers and viaducts from scratch? I guess you have to make a mold and use a release agent but I wanted to check with you experts first. I read where one guy carved the orginial in wood first and then made a rubber latex mold to duplicate several but there must be an easier way----I hope.
  2. G Pfeifer

    G Pfeifer New Member


    You can pour a sheet of plaster of paris about a quarter inch thick, then cut shapes such as a viaduct, portal etc, then take the smallest screw driver from a micro set and carve rock shapes into the plaster. Works good. I just take a flat piece of scrap plywood, glue some quarter inch square balsa sticks down to form the size square that I need, lay piece of wax paper down, put a piece of fiberglass mesh tape down to re-enforce it, and pour the plaster. After a little practice, carving the rock shapes is easy.

  3. XavierJ123

    XavierJ123 Member

    Thanks George----
    I have the day off and will try your suggestion immediately. I really appreciate your instructions and will let you know how it turns out.
  4. XavierJ123

    XavierJ123 Member

    Hey George:
    Everything turned out great--except the paint job. I made a mold for a tunnel portal and poured in the plaster-of-paris which needs to be a little thinner the next time. It didn't pour too well because it was too thick--but I managed. Almost immediately I removed the wood and the styrofoam arch pattern. This was easier than I thought. Then I used a pencil to sketch the large stone which decorate the portal arch, etc. I used an old wood chisel to lower the depth of the plaster so the decorative stone protuded somewhat and created a horizontal stone decor at the very top of the portal. After trying a small screwdriver to carve the stone, I found using my Dremel tool with the smallest attachment available worked best. At first, I could not control the Dremel to my liking. I then used a small piece of scrap wood as a straight edge to keep the Dremel tool from wandering. The decorative stone turned out nice. I decided to paint it right away and used burned umber with lots of water. I think it is too dark--no matter how much I dilute it with water. So I started washing it with a light grey paint but I can't overcome the dark burned umber. It looks more like stained wood than stone. I had read somewhere to use burnt umber. Live and learn. Maybe it will dry lighter and look better.
  5. XavierJ123

    XavierJ123 Member

    Hey gang: My second attempt was a disaster. I think I used too much water in an attempt to make the plaster pour easier. Consequently the piece broke when I removed its' supports. At first I thought I could glue it back together after it dried more but needed to carve it first while the plaster was still soft. I started to carve the soft plaster but it broke again. I think I need to learn the proper proportions of plaster and water.
  6. ezdays

    ezdays Out AZ way

    You could try strengthening the plaster by putting some fine wire mesh inside, or even a piece of cloth. Also, if you need more set time, you might check with a local art store and see if they have anything that would retard the hardening process, or even some slower setting plaster.

    Good luck
  7. jimmybeersa

    jimmybeersa Member

    Two wee tips....I use the plaster that the Dry walling guys use ,here it called Rhinocrete,its a gypsem based plaster. Next mix it with water that has a few drops of dishwasher liquid added . Another thing I have used is that playdough the kids play with and Bake it in the Oven or micro wave oven ( when the management has gone shopping ) found a tip in a cookbook that says play dough can be made with flour and wallpaper glue to which can be add paper mulch for strength Have fun !!!!
  8. XavierJ123

    XavierJ123 Member

    Third time's charm

    Third time's charm. Sunday morning I poured a fresh batch of plaster-of-paris into the same portal form; only this time I watched my mixture more carefully and didn't make it "too soupy." I guess you could use a "soupy mixture that is easier to pour---you just have to let it dry longer. Perhaps I am impatient. At any rate, I just barely got the plaster into the form when it started to set up---in no time---just like the first batch. Maybe after a minute or so, I removed the form and and saw a nice portal before me. I immediately started carving the stone face on to the portal with my dremel tool. I carved massive decorative stones that follow the interior arch of the portal and the horizontal top. Brick was etched everywhere else with an exacto knife. I guess it is true; practice makes perfect. Can't wait to paint it. I would like to here any and all paint recommendations. I am always open to new ideas.
  9. 77railer

    77railer Member

    How about some pictures. I think they woudl be most helpful.
  10. jim currie

    jim currie Active Member

    if you can find it hydrocal is a exultant plaster for casting's strong fast setting also carves well.
  11. jasbourre

    jasbourre Member

    How are you coming allong with your portal, have you been able to take any pictures.
  12. XavierJ123

    XavierJ123 Member

    I have been vacaioning with my family in Myrtle Beach, South Carolina at the beach. Couldn't surf fish so we went to Broadway at the Beach, a Disney-like shopping complex around a lake. There is a Christmas store there that has a tri-level train display ( Lionel, HO and N scale ) with trains running around lots and lots of department 56 houses. They also sell the G and O gauge. The prices are about the same as a LHS. They have a lot of train sets, track and supplies including Woodland Scenics. I didn't buy anything.
    My wife is the digital picture wizard. Hopefully, she can figure out how to include a picture of the viaducts in the next post when we return home. My daughter was kind enough to allow me to use her laptop to type this reply. We are still lost down South in the sticks somewhere.
  13. vanda32547

    vanda32547 Member

    How about some pictures of your plaster project?

  14. CAS

    CAS Member

    I was wondering the same yhing.
  15. doctorwayne

    doctorwayne Active Member

    You can make moulds from .060 sheet styrene, most of the ones that I've made are two piece moulds. I use cooking oil, wiped on sparingly with a paper towel, as a mould release. For the actual pier or abutment, I use a product, available at places like Home Depot, called Durabond 90. It's a patching plaster that you mix with water to whatever consistency you require, and is available in anything from 2 lb. boxes to 33 lb. bags. In about 90 minutes it will set and the mould can be removed. Depending on the size of the casting, it may take a couple of days to completely harden, and I do mean harden. If you wish to carve in stone detail, etc., do it before it gets too hard. It can be filed, drilled, or cut with a saw, but it will dull tools quickly. I have cast bridge piers and abutments in HO scale from 10' to 50' high, some with integral wings and with stepped or notched tops. When I require several similar style piers of varying heights, I make a mould for only the tallest. By designing the mould to stand upside down while being filled, the shorter piers can be cast in the same mould by filling it only to the required height. The finished castings can be stained or painted: I use a very thin wash of Polly Scale (a few drops in a cup of water, applied with a brush. When this dries, I use an airbrush to add rust stains and high water marks. Hope this is of some assistance.

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